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Effects of environmental moisture and precipitation on insects: A review
Abstract
Climatic factors are closely related to the individual's development and growth, and the population dynamics of insect pests. Environmental moisture (including atmospheric relative humidity and soil moisture content) can directly cause the changes of insects' water content and destroy their water balance in vivo, and consequently, affects their individual's development and population occurrence. As resulting in the changes of environmental moisture, precipitation can also affects field population dynamics of insects by physically washing out. Therefore, the studies on the impacts of environmental moisture and precipitation on insects have a wider significance for the integrated pest management (IPM). This paper reviewed the impacts of environmental moisture and precipitation, as well as other environmental factors ( e. g., temperature), on the growth and development, survival, behavior, reproduction, and population ecology of insects, and introduced the applied studies on the regulation of environmental moisture (e. g., via irrigation) to control the occurrences of insect pests (e. g., Helicoverpa armigera) in fields.
... The relative humidity is believed to influence the water balance of insect organisms, induce outbreaks of pathogenic microorganisms, and indirectly influence insect feeding by controlling the moisture content of host plants Lin et al. (1998), Bale et al. (2002), Chang and Gao (2008) Total precipitation during the growing season ( The same as ETP -Effects of meteorological factors on the defoliation dynamics of the larch caterpillar… structure of our sampling data allows us to add a flexible random effect in the regression model to address individual differences among forestry bureaus. Such mixed effects modeling consists of fixed and random components. ...
... Humid environments, especially those that have almost continuous drizzle, may exacerbate spore dispersal of Beauveria bassiana, recognized as an important pathogenic bacterium that can trigger a sharp decrease in larch caterpillar populations because the early instar larvae are vulnerable to disease (Xu et al. 2008a;. Nevertheless, exposure to high or insufficient humidity for lengthy periods can generate adverse effects on development or survivability of insects because such conditions can directly modulate the interior water balance of the insect body (Tauber et al. 1998;Han et al. 2004;Chang and Gao 2008) Persistent low humidity can lead to high mortality in insects via dehydration (Rouault et al. 2006). From this perspective, relationships between relative humidity and defoliation area were expected to be nonlinear as a result of adverse effects at both extremes. ...
... Trends of a annual mean temperature, b relative humidity, and c precipitation represent a warmer and drier climate in the Great Xing'an Mountains since 1975, based on five weather stationsTable 1Review of the potential effects of weather conditions on larch caterpillars (and some other forest insects) at different periods of the life cycle Period of life cycle Egg stage and hatching period (June-July) Mean daily relative humidity (BMRH) Extreme variation in relative humidity can influence the egg hatching process and subsequent survival rates, and it may exacerbate dispersal of pathogenic microorganismsYu and Yin (1980),Lin et al. (1998),Han et al. (2004),Chang and Gao (2008),Bale and Hayward (2010) Total precipitation (BTP)Precipitation may produce adverse effects on adult copulation and mechanically injure eggs and hatched larvaeHan et al. (2004),Tang and Niu (2010),Björkman et al. (2011), Hou et al. (2012,Yu et al. (2013),Khaliq et al. (2014) ...
Larch caterpillars are widely distributed in the Great Xing’an boreal forests; however, the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood. The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors. The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics. The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area, while rainy and humid growing seasons decrease the defoliation area. Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect, followed by the accumulative temperatures of the late instar larval period which had a positive impact, and precipitation during the middle instar larval period which had a negative impact. Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40% of the explained variance. This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.
... This observation aligns with the findings of Vidya et al., (2011) [11] , where the abundance of insect pests on cruciferous vegerables increased with higher temperatures in the Nilgiri district of India. Relative humity also has a significant impact on insect life, influencing their development and reproductive activities either directly or indirectly (Chang et al., 2008) [12] . In this study, insect pest frequency showed a negative correlation with relative humidity, indicating that as humidity increased, pest frequency decreased. ...
... This observation aligns with the findings of Vidya et al., (2011) [11] , where the abundance of insect pests on cruciferous vegerables increased with higher temperatures in the Nilgiri district of India. Relative humity also has a significant impact on insect life, influencing their development and reproductive activities either directly or indirectly (Chang et al., 2008) [12] . In this study, insect pest frequency showed a negative correlation with relative humidity, indicating that as humidity increased, pest frequency decreased. ...
... This observation aligns with the findings of Vidya et al., (2011) [11] , where the abundance of insect pests on cruciferous vegerables increased with higher temperatures in the Nilgiri district of India. Relative humity also has a significant impact on insect life, influencing their development and reproductive activities either directly or indirectly (Chang et al., 2008) [12] . In this study, insect pest frequency showed a negative correlation with relative humidity, indicating that as humidity increased, pest frequency decreased. ...
... This observation aligns with the findings of Vidya et al., (2011) [11] , where the abundance of insect pests on cruciferous vegerables increased with higher temperatures in the Nilgiri district of India. Relative humity also has a significant impact on insect life, influencing their development and reproductive activities either directly or indirectly (Chang et al., 2008) [12] . In this study, insect pest frequency showed a negative correlation with relative humidity, indicating that as humidity increased, pest frequency decreased. ...
The present study examines the insect diversity in the Poba Reserve Forest, identifying 8 families, 2 orders, and 17 insect species. The two insect orders observed were Coleoptera and Hemiptera, with Coleoptera being the most abundant, constituting 75% of the total insect population, while Hemiptera accounted for 25%. Among the 9 insect families recorded, Cerambycidae was the most dominant, representing 40% of the total insect diversity, followed by Chrysomelidae at 32%. Other families observed in smaller proportions include Scarabaeidae, Bastrichidae, Curculionidae, Rhopalidae, Cicadidae, Flatidae, and Pyrrhocoridae, each making up 5% of the total. The study highlights the significant dominance of beetles (Coleoptera) within the forest ecosystem and underscores the need for further investigation into the ecological roles these insects play in forest health and biodiversity. The findings provide valuable baseline data for future conservation efforts and pest management strategies in the Poba Reserve Forest, emphasizing the importance of understanding insect dynamics in maintaining ecological balance.
... Climatic factors exert a great influence on the growth, development, distribution and population dynamics of insect pest (Chang et al., 2008). Both the physical and biological factors are much vital causing the variations in the densities of aphid population (Naeem, 1996 A range of maximum temperature 20.5-27.5°C ...
... Climatic factors play an important role in the fluctuation of the population of the insect pests and put forth a great pressure on the population Chang et al. (2008). (Naeem, 1996) suggested that physical and biological factors cause variation in the insect pest population. ...
Vegetables are grown in the widely diversified agro-climatic zones of Pakistan. Insect pests of vegetables are one of the main factors affecting the production of vegetables. They attack vegetable plants immediately after planting and continue till harvest. The aim of the present study was to investigate the seasonal outbreak of insect pests of vegetables in relation to the abiotic factors and to obtain comprehensive information on pest management practices of the farmer growing vegetables and the pesticide use pattern in commercial vegetable cultivation in the pocket area in vegetable production in Faisalabad, Punjab. The results of present study revealed that tomato and brinjal aphid Aphis gossypii attained peak during the 2nd week of February and showed negative correlation at maximum and minimum temperature while a positive correlation was recorded for relative humidity. Tomato fruit borer Helicoverpa armigera attained peak during 4th week of May and showed positive correlation with maximum and minimum temperature whereas negative correlation was observed between tomato fruit borer Helicoverpa armigera population and relative humidity, while the farmer practices indicated that the farmer adopt differently plant protection strategies which mainly focus on over and heavy use of pesticides on these crops. As the pesticide applications are repeated at three days interval, therefore, there is much chance that the application of pesticides will not only damage the environment but also incurs severe health concerns on the end consumers.
... We aimed to model the current distribution of species, as well as to infer the current patterns of taxonomic and phylogenetic diversity (as described further below) for hawkmoth species in the study area. We proceeded as follows: (1) (temperature seasonality), Bio05 (max temperature of warmest month), Bio12 (annual precipitation) and Bio15 (precipitation seasonality; Chang et al., 2008;Hasenpusch et al., 2012). Compared with other limiting environmental factors (e.g. ...
Aim
Rapid loss in global insect diversity has generated substantial public worry due to their critical ecological roles. However, there is controversy about the effectiveness of the global‐scale hotspots in guiding the conservation of diversity at the regional scale. Even worse, little is known about the knowledge of insect distributional dynamics in many understudied regions, such as East and Southeast Asia. Here, to guide for setting regional‐scale conservation priorities for insect diversity, we explore hawkmoths (Lepidoptera: Sphingidae) for their distributional dynamics and identify regional hotspots requiring protection.
Location
South China (including Guangdong, Guangxi, Hainan, Hong Kong and Macau) and northern Vietnam (17°~26.5° N, 102°~117.5° E).
Methods
Species distribution models were generated for 194 hawkmoth species based on 3597 occurrence records to predict their distributions. We calculated the spatial patterns of taxonomic and phylogenetic diversity and identified regional hotspots. Furthermore, the potential assembly mechanisms underlying insect diversity were explored by analysing the rates of speciation, extinction and dispersal between phyloregions.
Results
(a) The coastal regions of South China and northern Vietnam represent a regional hotspot of hawkmoths in East and Southeast Asia, with significantly higher α‐diversity than that in inland regions. (b) Dispersal played a more important role than local speciation and extinction in the formation of regional hawkmoth hotspots.
Main Conclusions
In this study, the ‘Out‐of‐the‐tropics model’ can explain the formation of the hawkmoth regional hotspots and the enhanced version of the ‘Pure dispersal model’ can explain the formation of the hotspots in Hainan Island. Compared with the local speciation and extinction, dispersal is the main driving factor that promoted the formation of the regional biodiversity hotspot of hawkmoths in South China. The case of Hainan Island suggests that protection within hotspots needs to account for specific regional macro‐evolutionary dynamics rather than indiscriminate coverage of identified hotspots.
... In southern China, the dry season is usually from February to April, when locust eggs hatch. Therefore, precipitation of wettest quarter (bio14) is important factors affecting the survival of C. nigricornis (Chang et al. 2008). Similarly, June to August is the key period for adult emergence, and insufficient precipitation will increase the risk of water loss of larva (Dang and Chen 2011). ...
Ceracris nigricornis Walker is an insect of the Acrididae, which can harm bamboo, rice, corn, sorghum and other crops, and can cause serious economic losses. In this study, based on 234 occurrence sites of C. nigricornis obtained from the Global Biodiversity Information Facility and literature, and data of three future climate scenarios presented by CMIP6, two niche models (GARP, MaxEnt) were used to predict the suitable area of C. nigricornis in China. The result shows that the main environmental factors affecting the distribution of C. nigricornis are min temperature of coldest month (bio6), mean temperature of coldest quarter (bio11), precipitation of driest month (bio14) and precipitation of wettest quarter (bio16). From the result of MaxEnt model, it can be seen that the suitable area of C. nigricornis in China is 128.91 × 10⁴ km² under current scenario. It will decrease by 3.19% in the 2050s and then increase by 12.04% in the 2090s under the SSP1‐2.6 scenario, increase by 5.79% in the 2050s and then decrease by 7.53% in the 2090s under the SSP2‐4.5 scenario, and increase by 33.03% in 2050s and then decrease by 23.31% in the 2090s under SSP5‐8.5 scenario. From the result of GARP model, it can be seen that the suitable area of C. nigricornis in China is 166.09 × 10⁴ km² under current scenario. It will increase by 8.41% in 2050s and then continue to increase by 6.11% in 2090s under SSP1‐2.6 scenario, increase by 23.84% in the 2050s and then decrease by 0.88% in the 2090s under the SSP2‐4.5 scenario, and increase by 34.37% in 2050s and then decrease by 1.75% in 2090s under SSP5‐8.5 scenario. The boundaries of suitable areas will expand to the north and southwest of China under future climate change scenarios, specially in Sichuan, Chongqing and Yunnan. Local forestry authorities should strengthen the monitoring of bamboo forests to prevent the damage caused by the introduction of C. nigricornis.
... This is consistent with the results of our work ( Figure 8B,C). Furthermore, lots of studies have shown that environmental humidity can affect the growth and development of insects [52][53][54]. The tolerance to humidity was relatively high, and O. rhinoceros can develop normally at a relative humidity of 85-95% [12], and the distribution of O. rhinoceros was positively correlated with humidity [55]. ...
The Asiatic rhinoceros beetle, Oryctes rhinoceros (Linnaeus, 1758) (Coleoptera: Scarabaeidae), is a destructive invasive species that poses a serious threat to palms, oil palms, and other plants. Defining a suitable area for the distribution of O. rhinoceros is essential for the development of appropriate policies and preventive measures. In this work, the MaxEnt niche model and ArcGIS software were used to predict the potential geographic distribution of O. rhinoceros in the world based on occurrence data and related environmental variables and to speculate on the influence of environmental variables on the distribution of O. rhinoceros. The results showed that the suitable areas of O. rhinoceros beetle were mainly distributed in 30° N–30° S, and the highly suitable areas were concentrated in South Asia, East Asia, Southeast Asia, and northern Oceania. The key environmental variables that determine the distribution location of O. rhinoceros are Precipitation of Wettest Month (bio13), Temperature of July (tmin7), Minimum Temperature of November (tmin11), and Precipitation of September (prec9). The prediction results of the MaxEnt model can reflect the global distribution of O. rhinoceros. This study can provide a theoretical basis for the prevention and control of O. rhinoceros and the development of relevant quarantine measures.
... Climate including temperature and precipitation plays a crucial role in the distribution of insects [6]. The survival and development of insects are influenced by temperature, which impacts their metabolic processes [35], and precipitation, which affects their water balance within the idiosoma [36]. In this study, we found that the contribution (91.4%) and the permutation (96%) of climate factors were significantly greater than those of soil, indicating that the distribution of N. asiatica was primarily influenced by climate rather than soil. ...
Climate warming affects the growth and development of pests, resulting in changes in their geographical distribution, which increases the difficulty in terms of prevention and control. The fruit fly, Neoceratitis asiatica (Becker), is a predominant frugivorous pest that causes serious yield loss in the goji berry, Lycium barbarum L. In recent years, with the expansion of cultivation area, the damage induced by the pest has become increasingly severe, significantly impeding the production of the goji berry. In this study, the potential suitable habitats of N. asiatica under current and future climate scenarios were simulated and predicted using the optimal MaxEnt model, based on the screening distribution records and environmental factors. The changes in the pest distribution under climate change were determined using ArcGIS. The results showed that the best combination of parameters for MaxEnt were feature combination (FC) = LQPT and regularization multiplier (RM) = 1. The dominant environmental factors influencing pest distribution were mean temperature of driest quarter, mean temperature of coldest quarter and precipitation of coldest quarter. Under different climate conditions, the suitable habitats of the pest primarily ranged between 27°–47° N and 73°–115° E. Under current climate conditions, the area of moderately and highly suitable habitats was 42.18 × 104 km2, and mainly distributed in Inner Mongolia (13.68 × 104 km2), Gansu (9.40 × 104 km2), Ningxia (5.07 × 104 km2), Qinghai (4.10 × 104 km2), and Xinjiang (3.97 × 104 km2) Provinces. Under future climate scenarios, the suitable area was projected to be lower than the current ones, except SSP245–2050s and SSP370–2070s, and the centroids of suitable habitats were mainly shifted to the northeast, except SSP370–2050s and SSP585–2070s. Our results provide valuable guidance for the monitoring and management of N. asiatica, as well as the selection of pest-free goji berry cultivation sites.
... June to August is the wettest month and the warmest month, and is the key period for adult emergence from the biological characteristics of C. kiangsu. At this time, insufficient precipitation will increase the risk of water loss of larva 30 , while excessive precipitation www.nature.com/scientificreports/ will increase the mortality of larva. ...
Ceracris kiangsu Tsai (C. kiangs) is a kind of forest pest, which can harm nearly 100 kinds of weeds and crops. In this study, based on 314 species distribution points of C. kiangsu which were obtained from Chinese herbaria, literatures and investigation, and data of three future climate scenarios presented by CMIP6, two niche models (Garp, Maxent) were used to predict the suitable area of C. kiangsu in China. The result shows that the main environmental factors affecting the distribution of C. kiangsu are precipitation of driest month (bio14) and min temperature of coldest month (bio6). No matter now and future, the potential distribution areas of C. kiangsu in China are mainly in the south of Qinling–Huaihe River. Under current scenarios, the areas of the total, highly, moderately and poorly suitable of C. kiangsu in China are 160.65 × 10⁴ km², 31.70 × 10⁴ km², 60.36 × 10⁴ km² and 68.59 × 10⁴ km² respectively. The southern Hubei, western Jiangxi and eastern Hunan are highly-suitable areas. Under SSP1-2.6 and SSP2-4.5 scenarios, both the total suitable area and the highly suitable show a decreasing tread in 2050s. Compared to the 2050s, the total suitable area will coninue to decease in 2090s under SSP1-2.6, while it will increase under SSP2-4.5. The highly suitable area will increase in both scenarios, and the increased percentage under SSP2-4.5 is greater than that under SSP1-2.6. Under SSP5-8.5 scenarios, the total suitable area will increase by 1.83% in the 2050s, and decrease by 1.17% in the 2090s. The highly suitable area in the 2050s and 2090s under this scenarios is larger than under current scenarios. No matter what the scenario, the southern part of Yunnan, the southeast of Sichuan and the southwest of Chongqing will become highly-suitable areas as the climate continues to warm and should be monitored more cosely.
... Soil type and soil moisture that affect the survival of the subterranean pupae (Beirne 1970) could explain the disparity between the predicted and realized results. Chang et al. (2008) reported that moisture could directly alter the water balance in insects, which may affect their growth and population dynamics. Indeed, the minimum precipitation of the driest month was determined to be the most important variable in the models. ...
Two Mexican leaf-feeding beetles, Zygogramma piceicollis (Stål) and Zygogramma signatipennis (Stål) (Coleoptera: Chrysomelidae), were released in South Africa for the biological control of the invasive species Tithonia rotundifolia (Mill.) S.E. Blake (Asteraceae: Heliantheae). The aim of this study was to predict the potential of these beetles to establish and spread in South Africa, using MaxEnt climate modelling that incorporated locality data recorded in Mexico between 2008 and 2019 and data from the Global Biodiversity Information Facility. Zygogramma signatipennis displayed a wider distribution than Z. piceicollis in Mexico, with some overlap between the two species. The average receiver operating characteristic curves obtained for Z. piceicollis and Z. signatipennis predicted high mean area under curve values of 0.910 and 0.885, respectively. Jackknife tests revealed that mean annual temperature had the highest gain when used in isolation for Z. piceicollis , compared with minimum precipitation of the driest month for Z. signatipennis . These tests also revealed that the highest and lowest contributing environmental variables for Z. piceicollis and Z. signatipennis were minimum precipitation of the driest month (37.9 and 46.7%) and maximum annual temperature of the warmest month (3.8 and 12.3%), respectively. MaxEnt modelling predicted that at least six of South Africa’s nine provinces provide regions that would support the proliferation of both beetles, with conditions best suited for Z. piceicollis . Despite predictions that both beetles should establish throughout the range of T. rotundifolia in South Africa, their realized establishment has so far been poor. Other factors, besides climate, including release size, site destructions, drought, soil moisture and texture could be constraining establishment.
... This could suggest that these temperature and relative humidity best-practices might not be feasible for collections in other climates such as tropical or subtropical regions (Bickersteth, 2014;Kirby-Atkinson, 2014;Staniforth, 2014;Inuzuka, 2016). Multiple previous studies in agriculture have linked the effects of temperature and humidity to reproduction, growth, and development of invertebrate pests (Chang et al., 2008;Norhisham et al., 2013;Zulfiqar et al., 2010). These studies suggest that surpassing certain levels of maximum temperature or relative humidity in a closed environment such as our herbarium could stimulate invertebrate growth. ...
Herbaria are natural history collections that host a vast amount of information on plant taxonomy, biology, distribution, and genetic diversity, and are therefore are a key resource for scientific research. However, changes in environmental conditions can make these collections highly susceptible to pest infestations. Maintaining relative humidity (RH) and temperature control within herbaria can help preserve plant specimens. The role of these variables has not been properly studied in tropical regions, especially in relation to the abundance of invertebrates that can infest collections. In this study we use daily temperature and RH measurements, and data from invertebrate pest traps collected quarterly between 2017-2021 in the CDS herbarium of the Charles Darwin Research Station. With these data, we test for 1) the effect of ambient conditions on invertebrate abundance in the herbarium, 2) the effect of surpassing the recommended temperature and RH thresholds on invertebrate abundance, and 3) the correlation between herbarium ambient conditions and outdoor weather data, in order to evaluate the effectiveness of environmental controls. Our results show a significant positive correlation between periods of high temperature and the abundance of invertebrates, increasing the number of individuals by 32.4% per 1ºC (±12.7 S.E., p = 0.02), but no significant effects on potential pests. We also found a significant correlation between outdoor and indoor environmental conditions. These results suggest that despite imperfect environmental controls, best practice recommendations of 40-55% humidity and temperature of 21-23ºC are most appropriate for maintaining invertebrate pest control. In this case, work is needed to ensure temperature is maintained below 23ºC to prevent growth and spread of invertebrates in collections. Altogether, this study shows the direct relationship between environmental conditions and the abundance of invertebrates, and stresses the importance of maintaining ambient control in natural history collections in tropical climactic regions.
... Therefore, FAW could pose a danger to several crops in a region. These biotic potentials of FAW could provide an ability to invade a wide range of host plants and to be adapted with appropriate climatic factors to reproduce with a higher reproductive rate in many world regions (Chang et al., 2008). ...
The fall armyworm [FAW; Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae)], is considered a serious invasive pest that poses a serious threat to world food security. It can completely devastate a whole country's cereal crops. Therefore, the present work is the 1st field trial in Egypt to elucidate some ecological aspects of S. frugiperda on maize plants (Single-Hybrid 168 Yellow Corn cultivar) at Esna district, Luxor Governorate, Egypt, throughout two sequential growing seasons of maize (2021-2022). Three insect parameters were used, i.e., egg masses, number of larvae, and percentage of damaged corn plants. Effects of certain climatic conditions and corn plant ages on S. frugiperda seasonal activity and damaged plants percentage were also estimated. S. frugiperda population initiated to attack maize plants from the 3rd week of June until the harvest in every season. S. frugiperda had two seasonal activity peaks in terms of egg masses numbers and three peaks regarding the larval population density/season. Its damage percentage increased with increasing plant age weekly. The mean of S. frugiperda egg masses were 2.83 ± 0.40 and 2.96 ± 0.45 mass /10 corn plants in 2021 and 2022, respectively. While, the overall mean larval populations were 13.41 ± 0.52 and 13.03 ± 0.46 larvae/10 plants, during the two growing seasons, respectively. Corn plant damage percentages reached 68.54 ± 2.71 and 60.42 ± 2.92% in 2021 and 2022, respectively. The combined effects of both the weather conditions and maize plant ages were highly significant on egg masses, larvae population density, and damage percentage, and varied from one season to another. The mean daily maximum temperature was the most effective variable on egg masses and the larval population. Maize plant age had a clear effect on the damage percentage caused by the larvae in the field during the two years of the study. The dramatic spread of FAW and the consequent damage (that appeared in different countries of America, Africa, and Asia) mean that different management approaches must be sought for the small and large-scale producers by using available technologies for smallholder farmers will eliminate pest damage without access to reach to an economic Injury level. This information may assist the decision maker when planning the S. frugiperda IPM program for maize plants and its surveillance.
... • Humidity and Precipitation In general, precipitation as a non-biological factor affects the environmental temperature and humidity. Since temperature and humidity tend to cause changes in pest behavior, precipitation has a definite effect on pest phototropic rhythms (Chang et al., 2008), precipitation has a huge impact on the phototropic rhythm of pests. Pests are forced to land when it rains. ...
Pest management has been a great challenge since the beginning of human agricultural activities. Since the 1930s, chemical pesticide control has been a major control technology that can solve some of the pest problems in agricultural production. Still, it is harmful to food safety and the ecological environment. Meanwhile, the extensive use of chemical pesticides may lead to the rapid development of pest resistance. Because of the advantages of low cost, eco-friendly advantage, and low side effects, Solar Insecticidal Lamp (SIL) as the main physical control technology has been widely used for pest management in agricultural production in China. Owing to the phototaxis of pests, they have a phototropic rhythm during the nighttime. We can adjust the SIL insecticidal time according to the phototropic rhythm of pests. The purpose of this paper is to provide a comprehensive review of the pest phototactic rhythm in a selection of 24 pest species. It is the first comprehensive survey on the phototactic rhythm of pests and the time segments of this survey are accurate to the hour. The phototactic rhythm of pests are investigated in two different varieties of crops: 1) food crops and 2) economic crops. We also discuss and analyze the various factors (e.g., meteorological conditions, insecticidal devices, physiological states and others) that affect the changing phototactic rhythm of pests. Finally, we highlight some open research challenge issues and future directions.
... In relation to the use of water in agriculture, Climatic factors are closely related to the individual's development and growth, and the population dynamics of insect pests. Environmental moisture (including atmospheric relative humidity and soil moisture content) can directly affect their individual development and population occurrence (Chang et al., 2008). ...
... Precipitation variables also had direct and indirect effects on the distribution patterns of L. humile. Changes in precipitation affect the humidity and temperature of L. humile habitats, and thereby affect growth and development, survival, reproduction, and overwintering [41][42][43]. Our results indicate that the probability of the presence of L. humile was greatly affected by the precipitation of the coldest quarter. ...
Linepithema humile (Mayr, 1868) (Hymenoptera: Formicidae) is one of “100 of the world’s worst invasive alien species” listed by the International Union for Conservation of Nature and Natural Resources (IUCN). Although native to South America, this ant has spread worldwide via international trade. Currently, L. humile has not been found in China, and if it invades China, it might pose a potential risk to the native invertebrates, vertebrates, plants, and human livelihoods. Based on 2432 global occurrence records and ten bioclimatic variables, the optimized MaxEnt model was used to predict the potential suitable areas of L. humile in China. We analyzed the important bioclimatic variables affecting the potential suitable areas, and determined the changes in potential suitable areas under future climatic scenarios. Our results indicated that the mean temperature of the coldest quarter (Bio11), precipitation of the coldest quarter (Bio19), mean temperature of the wettest quarter (Bio8), and precipitation of the warmest quarter (Bio18) were the most important bioclimatic variables. Under the current climatic scenarios, the potential suitable area of L. humile in China is 80.31 × 104 km2, which is mainly located in Fujian, Zhejiang, Hunan, Jiangxi, Guangxi, Yunnan, and Hubei. Under future climate scenarios over coming decades, the potential suitable areas of L. humile showed an overall increase and a shift to higher latitudes, which indicated the invasion risk of L. humile in China will increase under climate change. Our findings provide the theoretical guidance for the early warning and monitoring of L. humile in China.
... Insects are adapted to live in wide temperature ranges, all the way from subzero to extremely hot temperatures, although each species has an optimal range of temperatures where their fitness is maximized (Chapman, 1998). Thermal and humidity stress are two of the most important barriers to the development and survival of insects (Chang et al., 2008;Richter et al., 2010). Since temperature gradients in the field can affect the physiology, reproduction, and distributions of insects, many of them with significant agroecological importance, research on their thermal thresholds remains a relevant scientific endeavor. ...
Climate change, particularly global warming, is disturbing biological processes in unexpected ways and forcing us to re-study/reanalyze the effects of varying temperatures, among them extreme ones, on insect functional traits such as lifespan and fecundity/fertility. Here we experimentally tested, under both laboratory and field conditions, the effects of an extreme range of temperatures (5, 10, 15, 20, 30, 40, and 45 °C, and the naturally varying conditions experienced in the field), on survivorship/lifespan, fecundity, and fertility of four pestiferous fruit fly species exhibiting contrasting life histories and belonging to two phylogenetic groups within the genus Anastrepha: A. ludens, A. obliqua, A. striata, and A. serpentina. In the field, we also measured the length of the entire life cycle (egg to adult), and in one species (A. ludens), the effect on the latter of the host plant (mango and grapefruit). Under laboratory conditions, none of the adults, independent of species, could survive a single day when exposed to a constant temperature of 45 °C, but A. striata and A. serpentina females/males survived at the highly contrasting temperatures of 5 and 40 °C at least 7 days. Maximum longevity was achieved in all species at 15 °C (375, 225, 175 and 160 days in A. ludens, A. serpentina, A. striata and A. obliqua females, respectively). Anastrepha ludens layed many eggs until late in life (368 days) at 15 °C, but none eclosed. Eclosion was only observed in all species at 20 and 30 °C. Under natural conditions, flies lived ca. 100 days less than in the laboratory at 15 °C, likely due to the physiological cost of dealing with the highly varying environmental patterns over 24 h (minimum and maximum temperatures and relative humidity of ca. 10–40 °C, and 22–100%, respectively). In the case of A. ludens, the immature’s developmental time was shorter in mango, but adult survival was longer than in grapefruit. We discuss our results considering the physiological processes regulating the traits measured and tie them to the increasing problem of global warming and its hidden effects on the physiology of insects, as well as the ecological and pest management implications.
... Also, during the analyzed two seasons, the dew point and mean daily minimum temperature were the most accurate variables for explanation differences in the insect population and, on the percentages of infestation incidences, as compared the three other variable (mean daily of maximum temperature, relative humidity and plant age). Climatic factors exert a great influence on the growth, development, distribution, and population dynamics of insect pests (Chang et al. 2008). Both the physical and biological factors are much vital causing the variations in the densities of aphid population (Naeem, 1996). ...
... For example, reproductive rates and metabolism of arthropods is often higher under warm conditions, possibly leading to higher densities and/or activity levels under low tunnels (Régnière et al., 2012). Lastly, the impact of moisture on invertebrate presence is less clear, but imbalances in relative humidly can disrupt water balances in vivo leading to reduced population density (Chang et al., 2008). However, humidity levels were similar across treatments for two of three years observed in this study, thus the impact of differential humidity on beneficial invertebrates is likely minor. ...
Although growing strawberries under low tunnels is increasing in popularity across the northeastern United States, little is known of how they impact the presence of natural enemies and pollinators that provide key ecosystem services on strawberry. We employed passive (fruit collections, sticky cards and pitfall traps) and direct (direct observations, leaf brushing and fruit bagging) monitoring over 2-3 growing seasons to compare the abundance and impact of beneficial insects and mites on strawberry grown under low tunnels versus the open field. Three different low tunnel plastics ranging in UV-selectivity were included to determine any effect of UV exclusion on natural enemy and pollinator presence. Plant yield and fruit marketability was higher under low tunnels compared to the open field for two of three years observed. The abundance of predators, and to a lesser extent parasitoids, was similar or higher under low tunnels compared to the open field. However, catch on sticky cards revealed lower densities of parasitoids under tunnels. There was some evidence that UV-selecting plastics resulted in poorly pollinated fruit compared to UV-transmitting and open-field treatments. However, there was no difference in pollinator presence among treatments, so the mechanisms causing the plastic effect are unclear. Overall, we conclude that growing strawberries under low tunnels, regardless of UV selectively, can support higher and more marketable yield in some years while likely having neutral to positive impacts on beneficial predators, parasitoids and pollinators.
... Moreover, the increased frequency of climate extremes can promote pest outbreaks (Gan 2004). Precipitation influences environmental humidity and the dynamics of insects, thereby affecting geographical distributions (Chang et al. 2008). In addition to precipitation, irrigation, another source of field water, affects the occurrence of species by influencing humidity and atmospheric conditions (Liang et al. 1998). ...
The codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) is a destructive pest of apple (Malus domestica (Rosales: Rosaceae)), pear (Pyrus spp. (Rosales: Rosaceae)), and other pome tree fruits; outbreaks cause significant ecological and economic losses. In this study, we used CLIMEX model to predict and evaluate the global risk of C. pomonella based on historical climate data (1989–2018) and simulated future climate data (2071–2100) under the RCP4.5 scenarios. Cydia pomonella exhibited a wide distribution under both historical and future climate conditions. Climate change is predicted to expand the northern boundary of the potential distribution from approximately 60°N to 75°N. Temperature was the most dominant factor in climatic suitability for the pest. Combinations of multiple meteorological factors (relative humidity and precipitation) associated with a failure to break diapause in certain regions also affect suitability, particularly in northern South America and central Africa. Irrigation only had a slight impact on species favorability in some areas. The projections established in our study present insight into the global potential suitability of C. pomonella under climate change scenarios by the end of the 21st century. Farmers should be aware of the risk associated with the pest based on the results, which would provide guidance for quarantine agencies and trade negotiators worldwide.
... Furthermore, higher soil moisture status in RC systems without winter fallow can reduce the occurrence of a range of insect herbivores whose emergence, oviposition, survival, and habitation have been shown to be adversely affected by high moisture. 36 Specifically, high soil moisture has been shown to reduce the occurrence of moths (cotton bollworm, Helicoverpa armigera), 37 cutworms (Agrotis segetum), 38 common cutworm (Spodoptera litura) and beet armyworm (Spodoptera exigua). 22,39 Rice also supports crayfish production by providing habitats for crayfish, regulating temperature on hot days, 21 and providing additional feed sources, including from rice planthoppers and other planteating insects that fall into the water. ...
BACKGROUND
Rice‐crayfish coculture (RC) uses 10% of the paddy field area for crayfish ditches, with rice cultivated in the remaining area, providing staple carbohydrates alongside fish rich in protein and essential oils. These systems rely on complex interactions, involving nutrient cycling, fish feeding, soil physicochemical modification, and insect‐pest predation, and have important socio‐economic effects. Past studies have considered only one or a few of these aspects pertinent to food system sustainability, and there remains a need for an integrated assessment of RC systems. In this mini‐review, we collate data from two field experiments and three field surveys published across eight papers to synthesize the overall sustainability of RC systems in Jianghan Plain in China.
RESULTS
In deep groundwater fields, the RC rice yield was 30–55% lower than for typical rice‐rapeseed (RR) rotations, while CH4 emission and pesticide use were 41–96% and 50% lower, respectively. In shallow groundwater fields, RC rice yield was similar to typical rice monoculture (RM) cultivation, while CH4 emission and pesticide use were 28–41% and 17% lower for RC cultivation. Field survey data indicated that RC can improve soil nutrient and organic matter content significantly compared with RM cultivation, and also increase the diversity of fauna and flora in the paddy field whilst reducing the incidence of chilo suppressalis (a major rice pest). Feed inputs to RC systems increased crayfish yield by 31–71% and reduced the fraction of N inputs lost to the environment from 71% to 41%.
CONCLUSION
We conclude that RC systems with feed inputs in areas with shallow groundwater can deliver improved food security, sustainability, and resilience through ecological intensification. © 2020 Society of Chemical Industry
... Populations of herbivorous insects may have also been reduced by higher soil humidity, as excessive moisture has been showed to have disadvantageous effects on growth, reproduction, habitation and overwintering of herbivores (Esbjerg, 1988;Shipp et al., 2003;Chang et al., 2008). For example, high soil humidity interfered with the oviposition and development, and had an adverse effect on the population growth rate of S. litura (Yang, 2008). ...
Increasing agricultural biodiversity by diversifying crops or by co-culture of crops and aquatic animals has been widely recognised as a way to promote ecological intensification of crop production and reduce the use of pesticides. However, the potential of multi-trophic-level production systems, such as the co-culture of vegetables, flowers and aquatic animals, has received little attention. We performed a two-year experiment comparing multispecies (cauliflower, taro, flowers and aquatic animals) co-culture, and mono-cauliflower farming practices on the Chongming Eco-island of China. The abundance of herbivorous insects and their predators, pesticide input and cauliflower yield were recorded. The results indicated that multispecies co-culture decreased the abundance of insect herbivores by 19.9–26.0% and thus decreased pesticide use by 22.2–30.0%. Meanwhile, we found that co-culture of crops, flowers and aquatic animals increased the abundance (29.5–34.1%), and species diversity of invertebrate predators (3.3–3.8%), and increased cauliflower yield (6.9–7.5%). There were significant positive relationships between the abundance, species richness (or diversity) of arthropod predators and cauliflower yield. Multispecies co-culture has great potential to promote ecological intensification of vegetable production and the associated ecosystem services.
... Higher soil moisture is another factor that might affect the occurrence of insect herbivores, as excessive humidity has an adverse impact on emergence, oviposition, survival and habitation (Chang et al., 2008). For example, 83.3% moths (cotton bollworm, Helicoverpa armigera) failed to emerge when the soil moisture exceed 60.0% (Wu and Guo, 1997). ...
Global societies witnessed rapid increase in population and accelerating demand for vegetables from cities along the coastal areas (e.g., Shanghai). Development of “multiculture”, “polyculture”, or “co-culture” systems along the coastal areas in Southeast Asia in turn become a preferred choice for installing future aquaculture. To build much needed knowledge guiding the design, ecological benefits, and performances of these newly explored vegetable-aquaculture systems, we designed a nested block experiment and conducted a 3-year study of cauliflower-aquaculture farming on the island. We found that farming type significantly affected the arthropod herbivores and predators, including herbivore abundance and the abundance, species richness and Shannon's diversity of the predators. More importantly, farming type had a significant effect on insecticide use, cauliflower yield and economic returns. The reduction in insecticide use promoted predator diversity and cauliflower yield in co-cultured cauliflower aquaculture as indicated by a significantly negative relationship between amount of commercial insecticides and arthropod predator diversity, as well as between amount of commercial insecticide and cauliflower yield. We conclude that co-culture practice in cauliflower-aquaculture enhanced agricultural production while decreasing use of insecticide and herbivore abundance, and increasing the abundance and diversity of predators, vegetable yield and economic value.
... Climatic factors exert a great influence on the growth, development, distribution, and population dynamics of insect pest (Chang, et al. 2008). Both the physical and biological factors are much vital causing the variations in the densities of aphid population (Naeem, 1996). ...
... Weather factors play a vital role on the population dynamics, distribution growth and development of an insect pest (Chang et al., 2008). Rainfall, relative humidity and Temperature of the surrounding of the crop influence on build up and outbreak of insect pest population. ...
Five major cauliflower producing localities viz., Faisalabad, Chiniot, Sargodha, Sheikhupura and Gujranwala of Punjab, were selected to check the population fluctuation of S. litura larvae through regular ten days interval on cauliflower crop during 2013-14. The data were recorded at fixed schedule of Period I (22 to 31 August), Period II (01 to 10 September), Period III (11 to 20 September), Period IV (21to 30 September) and Period V (01to 10 October). During 2013 maximum larval population was recorded in Sargodha during 4th period of observation and minimum population was observed in Gujranwala during 1st period of observation i.e. 4.55±0.117 and 1.96±0.105 larvae/plant respectively. While during 2014 minimum population was recorded in Gujranwala (1.05±0.024 larvae/plant) during the 2nd period of observation and maximum population was observed in Sargodha during 1st period of observation i.e. 4.37±0.086 larvae/plant, respectively. Relative humidity and rainfall was negatively correlated with the larval population while, temperature was significant and positive correlated with larval population.
... The development, growth and population dynamics of an insect pest is greatly influenced by weather factors (Chang et al. 2008). Regression equations were developed to determine the role of climatic factors of temperature and relative humidity on the larval population after each observation and fruit infestation caused by H. armigera at the maturity of the crop at all the localities. ...
A survey was conducted in tomato fields at different localities to assess the distribution of tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) in Punjab Province, Pakistan. The effect of weather factors on its population was also investigated. Eleven tomato-growing districts were selected and data for larval population and fruit infestation were recorded. The maximum larval population (5.2 larvae/plant) of H. armigera was recorded in Bahawalpur district with 32.6% fruit infestation. However, the minimum larval population (1.4 larvae/plant) inflicted 14.7% fruit infestation in Rawalpindi district. The temperature was positively correlated while relative humidity showed negative interaction with the larval population and fruit infestation.
In order to find out the potential suitable areas of Ceracris Kiangsu Tsai in China, and do a good job in early monitoring. Based on 314 species distribution points of C.kiangsu which were obtained from Chinese herbaria, literatures and investigation, and data of three future climate scenarios presented by CMIP6, two niche models (Garp, Maxent) were used to predict the suitable area of C.kiangsu in China. The result shows that the main environmental factors affecting the distribution of C.kiangsu are precipitation of driest month (bio14) and min temperature of coldest month (bio6). No matter now and future, the potential distribution areas of C. kiangsu in China are mainly in the south of Qinling-Huaihe River. The southern part of Hubei, the western part of Jiangxi and the eastern part of Hunan are highly-suitable areas for C. kiangsu under current scenario. As the climate warms in the future scenarios, the southern part of Yunnan, the southeast of Sichuan and the southwest of Chongqing will also become highly-suitable areas. It can be seen that the local vegetation and climate conditions of these areas mentioned above are more suitable for the survival of C. kiangsu. It is recommended that the local forestry authorities strengthen the monitoring of bamboo forests to prevent the damage caused by the introduction of C. kiangsu.
Ambient humidity can directly affect the water balance in insects. The migratory fall armyworm, Spodoptera frugiperda Smith, has spread to more than 60 countries and regions in Africa, Asia, and Oceania that have a great difference in average ambient humidity. Understanding the effects of ambient humidity changes on its development, survival, and reproduction can help to predict its population dynamics in different habitats. Therefore, we evaluated the effects of atmospheric relative humidity (RH) on the development, survival, and reproduction and soil moisture on the pupation and emergence of fall armyworm. As a result, survival and pupal mass increased significantly with increasing RH. Among the five RHs tested, 80% RH was the most suitable for fall armyworm with the highest intrinsic rate of increase (r), finite rate of increase (λ), and net reproduction rate (R0). The population growth at the different RHs in decreasing order was 80 > 100 > 60 > 40 > 20%. A relative moisture (RM) of soil from 6.80 to 47.59% was suitable for fall armyworm pupation, survival, and eclosion, but fall armyworm could not pupate normally in soil with 88.39 and 95.19% RM. The survival and emergence rate of fall armyworm pupae were reduced by irrigation that increased the RM after the mature larvae entered the soil. These findings may be helpful for refining laboratory rearing protocols, population forecasting, and management of fall armyworm.
Zanthoxylum bungeanum is one of the important economic tree species in the programs for reforesting some of the cultivated land, afforestating barren hill, and conserving water and top soil in some areas of China. The relationships between the arthropod community characteristic and the meteorological factors, which include the lowest, highest and even air temperatures, the lowest, highest and even relative humidity, and the total rainfall in a month, in Z. bungeanum gardens near the Jinshajiang River in Yongshan County, Yunnan Province, China, were analyzed. The results showed that the species and individual number of phytophagous insects had the highest ratio in the arthropod community; the species diversity, evenness and abundance of the predatory and parasitic enemies were higher than those of phytophagous insects and neutral insects, and their dominant concentration index was relatively lower also; the neutral insects had higher dominance index and dominant concentration index, and the ratio of individual number of the dominant species was relatively higher. The arthropod community characteristic appeared seasonal variation rule evidently. The individual number of arthropod community increased rapidly from March, and reached the peak value in April. And then, the species and individual number of the nature enemies and neutral insects increased also. From late April to early June, the species diversity, abundance and evenness index reached the peak value, and the dominant concentration index decreased to the lowest value gradually. The heavy rainfall decreased every characteristic index of the arthropod community in July and August. The individual number of the community reached the second peak value in September. From the late October to January of the nest year, the species diversity, abundance and evenness index of the community decreased evidently. The lowest relative humidity was the most important factor affecting the individual number and the species number of the community, and the relationship of them was the positive correlation; the species diversity, abundance and evenness of the community correlated highly with the highest air temperature and the highest relative humidity, which indicated that in the higher temperature and humidity environment, the community had higher species diversity, abundance and evenness; the dominant concentration index and the dominance index correlated highly with the highest air temperature and the lowest relative humidity, which indicated that the higher air temperature or lower relative humidity was more suitable for the population increase of the dominant species; the stability indices Ss/Si and Sn/Sp, correlated highly with the mean relative humidity, which showed that the appropriate relative humidity was suitable for the increase of the restraining effect among the species. The affection of rainfall on the community characteristic was the weakest. From March to June, and from September to February of next year, which had less than 99.3 mm precipitation a month, the community characteristic index was positive correlation with the rainfall. In July and August, which had more than 164.5 mm precipitation a month, the community characteristic index was negative correlation with the rainfall. Comprehensive analysis showed that there were the close relationships between the meteorological factors and arthropod community characteristic. As the measurement and analysis of the air temperature, humidity and rainfall was more convenient, the analysis method of this paper has its practical significance for the research of variation rule of the arthropod community characteristics and the occurrence of pest population.
The occurrence of climate changes is evident from increase in global average temperature, changes in the rainfall pattern and extreme climatic events. These seasonal and long term changes would affect the fauna, flora and population dynamics of insect pests. The abiotic parameters are known to have direct impact on insect population dynamics through modulation of developmental rates, survival, fecundity, voltinism and dispersal. The study was carried out in Vegetable fields of Ghulam Muhammad Abad, Faisalabad using randomized complete block design (RCBD) during Rabi season 2009-10. The observations on aphid incidence were carried out simultaneously on 5 randomly selected plants per plot, taking 3 leaves, that is, each from upper, middle and lower strata. Aphid population showed significant negative correlation with minimum and maximum temperature, whereas significant positive correlation with relative humidity, and non-significant negative correlation with rainfall. The determination of effects of different weather factors on population of aphids in tomato was essential for effective pest management.
The size of Aphis gossypii population in brinjal (Solanum melongena L.) crop field was assessed using a randomised complete block design in the Rabi crop season (2009–10) at Ghulam Muhammad Abad, Faisalabad, Punjab, Pakistan. The maximum aphid population was recorded in February. In this study we observed that aphid population started decreasing with time as the environmental temperature increased. Abiotic conditions played an important role and significantly affected the reduction in the number of aphids. Environmental variables, such as the maximum and minimum temperature, had significant negative effects, whereas relative humidity had a significant positive effect, precipitation had a non-significant negative effect on the Aphis gossypii population. Farming practices indicated that different plant protection strategies were adopted, which mainly involved the excessive application of pesticides. Given the frequency of aphids on brinjal crops and farming practices, there is a need to develop a crop protection package based on modern integrated pest management practices.
Zanthoxylum bungeanum (Rutaceae) is one of the most important economic plants in some areas of China, because Z. bungeanum could be used to mitigate water and soil loss through the reforestation of barren hillsides where cultivation and tree removal has occurred. The mechanisms of insect community dynamics and pest insect outbreaks can be identified through their relationship with environmental factors such as altitude, temperature, humidity and insect community characteristics. This study investigated the relationship between the environmental variables and insect communities in Z. bungeanum gardens near the Jinshajiang River, Yongshan County, Yunnan, China. Insect communities were sampled from seven different gardens at varying altitudes (low 450-750 m; medium 750-1300 m; high 1300-1550 m) from March to September, 2008. All data were analyzed using multivariate analysis of variance (MANOVA) and the level of correlation using the Gray-system theory. The results were: 1) Insect community structure varied with altitude, suggesting altitude is a key factor influencing insect communities in Z. bungeanum gardens; 2) Increases in altitude resulted in higher species diversity, evenness, richness, Ss / Si(the number of species divided by the number of individuals) and Sn / Sp(the number of natural enemy species divided by the number of phytophagous species) at lower altitudes followed by a decline at higher altitudes. However, the species abundance and dominance indices decreased at lower altitudes then increased at higher altitudes; 3) Where Z. bungeanum gardens grew under more extreme climatic conditions, such as higher temperatures and lower humidity at lower altitudes, or lower temperatures and higher humidity at higher altitudes, there were less diverse insect communities. Thus, insect community characteristics such as species diversity, evenness, richness, Ss / Si and Sn / Sp indices were lower and more unstable in gardens at lower and higher altitudes. The seasonal dynamics of insect communities at lower and higher altitudes changed more quickly compared with those at medium altitudes. The climatic conditions at the gardens at medium altitudes (750-1300 m) were more suitable for diverse insect communities with ideal temperatures and humidity. Thus, the number of insects at the individual and species level in gardens between 750 and 1300 m (medium altitude) were relatively higher compared with gardens at lower and higher altitudes. The insect communities at medium altitudes indicated better stability based on insect community diversity, evenness, richness, Ss / Si and Sn / Sp indices, which were higher compared with the other two altitudinal groups. In comparison with the gardens at low and high altitudes, the seasonal dynamics of the insect community at medium altitudes changed slightly; 4) The dominance indices for the insect communities were higher at 450-750 m and 1300-1550 m altitude gardens, but lower in the 750-1300 m gardens. Furthermore, the dominance indices at the low and high altitude gardens showed a more significant change among seasons compared with the medium altitude gardens. Overall, insect community dynamics in Z. bungeanum gardens (Yunnan Province) may be influenced by altitudinal factors such as temperature and humidity, affecting insect species and abundance in various sub-communities. The key influencing factors were the extremes of temperature and humidity. The stability of insect communities in Z. bungeanum gardens could be improved under suitable temperature and humidity conditions similar to those found between 750 and 1300 m.
The gnat Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) is an important pest of Chinese chive (Allium tuberosum Rottler ex Sprengel). Although B. odoriphaga outbreaks are thought to depend on soil humidity, the mechanism by which humidity affects the outbreaks is poorly understood. In this study, the life history of B. odoriphaga (Diptera: Sciaridae) on Chinese chive was studied with an age–stage, two-sex life table and with relative humidity (RH) at 50, 60, 70, or 80 %. The developmental time of eggs and larvae, total preoviposition duration, and total preadult duration were longer at 50 % RH than at higher RH values. The mean total preadult duration was 34.16 days at 50 % RH and ranged from 27.34 to 31.81 days at 60–80 % RH. The mean fecundity was significantly higher at 70 % RH (as high as 62.88 eggs/female) than at 50, 60, or 80 % RH (from 33.41 to 50.52 eggs/female). The intrinsic capacity of increase (r), net production rate (R
0), and finite rate of increase (λ) increased as RH increased from 50 to 80 %, and mean generation time (T) showed the opposite trend. This study provides insight into the phenology of B. odoriphaga and shows that high RH promotes outbreaks of B. odoriphaga.
Movements, distribution, and survival of Cyrtomenus bergi Froeschner were investigated in experimental vertical and horizontal soil moisture gradients. Soil moisture acted as an important guide for movement, and the insects were attracted to moist soil. In the horizontal soil moisture gradient, most insects remained at soil moisture levels far beyond field capacity, but emigrated at moisture levels below the wilting point. In vertical soil moisture gradients, C. bergi showed positive geotaxy when the top soil was moist. Conversely, emigration was induced in dry top soil even with favorable soil moisture below. High relative air humidity stimulated activity above the ground. C. bergi was generally found closer to the soil surface in the morning than in the afternoon, especially during the dry season. High relative humidity induced flight regardless of the soil moisture level.
A field experiment was carried out to elucidate movement of the burrower bug, Cyrtomenus bergi Froeschner, and its distribution in soil profiles under dry and rainy season soil moisture conditions. By combinations of dispersal restrictions we demonstrated that flying, walking on the soil surface, and shallow burrowing were all equally important ways of dispersal for insect adults during the rainy season. During the dry season, however, burrowing was inhibited, but flying and walking on the soil surface were significant. Nymphs dispersed by walking on the soil surface while burrowing capacity was low. Damage caused by C. bergi feeding did not vary between the 2 seasons, and the habitat of both adults and nymphs remained between the surface of the soil and 20 cm below. Interaction between vertical distribution and seasons was due to low survival at 0-10 cm during the dry season. The relatively higher abundance at 10-20 cm during the dry season was explained by low survival at 0-10 cm; this result contradicts previous suggestions that the higher abundance was due to downward movements.
Eggs of Heliothis armigera and H. punctigera were exposed once to a high temperature (35–44°C) at 2 humidities for various periods (1/12–4 h) 12–24 h after oviposition. In both species exposure to 35 and 38°C had little affect on hatching, but prolonged exposures to temperatures above 38°C decreased it. H. punctigera eggs withstood short exposures to high temperatures better than H. armigera. Long exposures to high temperatures retarded development in both species. H. punctigera required more time than H. armigera to complete development at all temperature-exposure combinations. High humidity prolonged development at high temperatures(> 35°C).
Cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a major pest of cotton and corn crops in northern China. A phenological differentiation between fourth generation cotton bollworms from cotton and those from corn fields was observed in northern China during 1999–2000. The proportion of pupation in late fall was marginally higher in cotton fields compared to that in corn fields; however, the proportions of fall emergence of moths from cotton fields were significantly higher than those from corn fields. The proportion of spring emergence of moths was also significantly higher for larvae collected from cotton (28.0%) than from corn (14.5%). The overwintering duration of females was significantly shorter than that of males in both crops. Moreover, the overwintering duration of bollworm populations from cotton was significantly longer than that from corn. The early spring population of H. armigera came from both cotton and corn fields, but the spring emergence of moths from larvae collected from cotton took about 5 days longer to reach 100% emergence compared to that from corn.
We performed a series of laboratory experiments to determine the effects of shade, soil moisture, and soil compaction on the selection of pupation habitats by wandering late-instar Oriental fruit flies, Bactrocera dorsalis (Hendel). Larvae showed a strong preference toward pupating in shaded rather than brightly lit areas, in moist rather than dry soil, and in soil with larger particle sizes. These behavioral preferences are likely to lead to clumped distribution of Oriental fruit fly pupae in natural habitats. The implications of this for management of localized populations by chemical and biological methods are discussed.
Desert stream insects may use rainfall cues to anticipate and escape flash floods, but this has been studied in few taxa.
We used controlled, replicated experiments to quantify the use of rainfall cues for flood escape in seven common desert stream
insects. The hemipterans Curicta pronotata and Aquarius remigis responded consistently to rainfall cues by crawling vertically away from the water, in such a way that they may escape flash
floods in nature. The coleopteran Gyrinus plicifer showed no response to rainfall cues. The hemipteran Ambrysus woodburyi did not exit the water but sought refuge under submerged rocks. Three taxa (Ranatra quadridentata, Corydalus texanus, and Rhantus atricolor) gave ambiguous results, although the latter apparently responded to environmental cues other than rainfall. We conclude
that rainfall cues are a sufficient mechanism for flood escape in some taxa, but other desert stream insects may employ different
strategies (behavioral, life history, or morphological) to survive floods.