Small-scale farmers in Northern Tanzania grow vegetables that include tomatoes, cabbages and onions and use many types of pesticides to control pests and diseases that attack these crops. Based on the use of questionnaires and interviews that were conducted in Arumeru, Monduli, Karatu, and Moshi rural districts, this study investigates farmers' practices on vegetable pest management using pesticides and related cost and health effects. The types of pesticides used by the farmers in the study areas were insecticides (59%), fungicides (29%) and herbicides (10%) with the remaining 2% being rodenticides. About a third of the farmers applied pesticides in mixtures. Up to 90% had a maximum of 3 pesticides in a mixture. In all cases there were no specific instructions either from the labels or extension workers regarding these tank mixtures. Fifty three percent of the farmers reported that the trend of pesticide use was increasing, while 33% was constant and 14% was decreasing. More than 50 percent of the respondents applied pesticides up to 5 times or more per cropping season depending on the crop. Insecticides and fungicides were routinely applied by 77% and 7%, respectively by these farmers. Sixty eight percent of farmers reported having felt sick after routine application of pesticides. Pesticide-related health symptoms that were associated with pesticides use included skin problems and neurological system disturbances (dizziness, headache). Sixty one percent of farmers reported spending no money on health due to pesticides. These results can be used to develop a tool to quantify the cost of pesticide use in pest management by small-scale vegetable farmers in Northern Tanzania and contribute to the reformation of pesticide policy for safe and effective use of pesticides.
‘Double-low’ (00) varieties of oilseed rape (Brassica napus L. var. napus) have lower seed concentrations of certain astringent chemicals than have ‘single-low’ (0) varieties and as a result it has been suggested that plants of the 00 varieties may suffer higher damage by mammal and bird pests. Regular damage surveys were conducted over the winter months on 23 farms where 0 and 00 varieties of oilseed rape were being grown in close proximity. Samples of foliage were taken each month and analysed for levels of S-methylcysteine sulphoxide (SMCO) and various glucosinolates. There was no evidence that either rabbits (Oryctolagus cuniculus) or woodpigeons (Columba palumbus) preferred to feed on the 00 rather than the 0 varieties. The two types did not significantly differ in the foliage concentrations of SMCO or any glucosinolate. The concentrations of all the chemical constituents analysed fell significantly between February and April. There were no significant correlations between the level of damage in a field and the concentrations of SMCO or glucosinolates in the foliage of the plants grown there. There were significant correlations between the SMCO and glucosinolate concentrations in the 0 and 00 varieties grown on the same farm. This suggests that factors associated with climate, geographical location, soil type and/or cultivation may have a greater effect on the foliage concentrations of these chemicals than has the variety of the plant.
The potential of benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) to trigger systemic acquired resistance (SAR) in tomato (Lycopersicon esculentum. Mill cv. Vollendung) plants against a yellow strain of Cucumber mosaic virus (CMV-Y) was investigated. Application of BTH, as a drench, 7 days before inoculation with CMV-Y, protected plants against the necrosis caused by CMV-Y. The resistance was evident as a decreased disease incidence and severity in BTH-treated plants. Twenty-one days after challenge inoculation with CMV-Y, the disease incidence in plants with SAR did not exceed 12.5% whereas, 91.7% of control plants were severely infected. The development of primary disease symptoms in BTH-treated plants was delayed for 7 days. The disease spread rapidly in control plants and by the end of the experiment almost all control plants showed severe mosaic and leaf necrosis. Results of enzyme-linked immunosorbent assay (ELISA) indicated that BTH treatment affected virus replication in protected leaf tissues. Analysis of the newly developed leaves of BTH-treated plants for virus antigen revealed that symptomless plants failed to support the replication of CMV-Y and the concentration of the virus in these plants was similar to that in uninoculated control plants.
A mixture of 1,3-dicloropropene 60.5% w/w and chloropicrin 33.3% w/w (Telone C35 EC) may be registered in Italy for soil drip fumigation. Five experiments on greenhouse tomatoes in Northern, Central and Southern Italy compared the effectiveness of this mixture in comparison with methyl bromide to find the optimum application rate in soils infested by Fusarium oxysporum f.sp. lycopersici, F. oxysporum f.sp. radicis lycopersici, Sclerotium rolfsii, Meloidogyne javanica and M. incognita. Its efficacy against F. oxysporum f.sp. radicis lycopersici and M. incognita was confirmed when applied to soils at 100, 200, 300 and 400 l ha−1 (132.4, 268.4, 402.6 and 536.8 kg ha−1) under gas-tight films with 15–45 mm of application water (900–1200 mg Telone C35 EC l−1). In sandy soils, with slight F. radicis lycopersici infections and with heavy nematode (M. incognita) attacks, the mixture, drip applied at 900 mg l−1 during late summer (fumigation: late summer; transplant: late-summer/autumn; last harvest: early spring), performed well up to 132.4 kg ha−1 (100 l ha−1). In sandy loam soils with slight F. radicis lycopersici infections and severe infections of F. lycopersici and galling nematodes (M. javanica), 268.4 kg ha−1 (200 l ha−1) of the mixture applied at 900 mg l−1 as a drip provided yields similar to those of methyl bromide treated plots both in spring and summer cycles. In sandy loam soils, the diseases (F. lycopersici, F. radicis lycopersici) were controlled at rates ⩾268.4 kg ha−1 (containing 90 kg ha−1 of chloropicrin), but the mixture was ineffective against Sclerotium rolfsii occasionally observed in sandy loam soils. In both sandy and sandy loam soils, no significant relationships were found between the rates of mixture applied (132.4, 268.4, 402.6 and 536.8 kg ha−1) and the degree of nematode infestation.
InLine (Dow AgroSciences LLC, Indianapolis, IN, USA), a commercial formulation of 1,3-dichloropropene (1,3-D; 61%) plus chloropicrin (33%), is one of the potential replacements to methyl bromide for soil fumigation. The efficacy of 12 InLine concentrations (80–19,520 μmol kg−1) to control five species of weed seeds and four soilborne pathogens was evaluated in a laboratory dose–response study after 24 h of exposure to fumigants in a sandy loam soil at 20 °C in microcosms. Logistic dose–response models were used to estimate the effective concentration to reduce weed seed and pathogen viability by 50% (LC50) or 90% (LC90). Among the weeds, the seed of Portulaca oleracea was the most sensitive to soil fumigation with InLine (LC50=352 μmol kg−1, LC90=583 μmol kg−1), followed by Stellaria media and Polygonum arenastrum with LC90 values of 780 and 1636 μmol kg−1 soil, respectively. The seeds of Malva parviflora and Erodium cicutarium were not sensitive to fumigation up to the highest InLine dose of 19,520 μmol kg−1 soil. Among the pathogens, Pythium ultimum (LC50=30 μmol kg−1 soil, LC90=46 μmol kg−1 soil) was the most sensitive and Verticillium dahliae (LC50=625 μmol kg−1 soil, LC90=2735 μmol kg−1 soil) was the least sensitive to InLine fumigation. Phytophthora cactorum and Fusarium oxysporum exhibited intermediate susceptibility to this soil treatment (LC50⩽397 μmol kg−1 soil, LC90⩽1113 μmol kg−1 soil). In this sandy loam soil, InLine at a concentration of 1636 μmol kg−1 reduced the viability of Portulaca oleracea, S. media, Polygonum arenastrum seeds and all fungi pathogens tested (except for V. dahliae) by 90% at 20 °C after 24 h exposure.
Small-plot research and large-field validations were conducted to determine the effect of 1,3-dichloropropene (1,3-D)+chloropicrin (Pic) application methods in combination with the herbicides pebulate and napropamide on pest control in fresh market tomato (Lycopersicon esculentum Mill.). In both the small-plot trials and the large-validation fields, various treatments compared the efficacy of soil fumigants and herbicides based on methyl bromide, in-bed and broadcast applications of 1,3-D+Pic, pebulate, and napropamide. The results consistently indicated that either in-bed or broadcast applications of 1,3-D+Pic in combination with pebulate and napropamide are equally effective against the weed Cyperus spp., the nematodes Tylenchorhynchus spp., Belonolaimus longicaudatus, and Meloidogyne spp., and the soilborne disease Fusarium oxysporum f.sp. lycopersici in fresh market tomato. Therefore, broadcast 1,3-D+Pic application can reduce personnel exposure and poisoning risks, without losing pest control efficacy.
Two application methods, single- and double-chisel injection of the fumigant nematicide 1,3-dichloropropene (1,3-D) were evaluated for efficacy and environmental fate in pineapple field experiments. The objectives were to compare the 1,3-D soil distribution between injection methods, evaluate volatile losses to the atmosphere, and to determine efficacy with each method. In a small-plot field experiment, 1,3-D (224, 337, and 393 1 ha−1) was manually injected 30 cm deep with fumiguns to simulate the commercial practice of a single- or double-chisel injection per planting bed. 1,3-D concentrations in the soil atmosphere and in soil samples were determined and compared to nematode control. In two large-scale field experiments, 1,3-D (224 1 ha−1) was applied with commercial injection equipment with and without polyethylene mulch. Air monitoring for 1,3-D showed a reduction in 1,3-D air emissions with single-chisel injection compared with double-chisel injection. In all experiments, the two injection methods resulted in equivalent 1,3-D concentrations in the plant line. Single-chisel injection resulted in improved retention of 1,3-D within the planting bed as shown by low 1,3-D soil concentrations in the interbed. Nematode counts and bioassay studies found equivalent nematode control in the planting bed with either injection method. The single-chisel method, however, resulted in reduced nematode control in the interbed region.
One hundred and fifty F6 inbred durum wheat lines derived from Kunduru-1149×Cham-1 cross were characterised in terms of their response to yellow rust (Puccinia striiformis) race population including Yr2, Yr6, Yr7 and Yr9 virulence genes. The results revealed that there is a considerable amount of genetic variation among these lines and yellow rust resistance in durum wheat is highly heritable (92%). Twenty-five of 150 lines (16.67%) were found totally immune, 104 of them (69.33%) were found to be resistant or moderately resistant while only 21 of them (14%) were found to be susceptible. Hence, 86% of the lines tested in this study could be used as a source of yellow rust resistance in breeding programmes.
We tested persistence and effects of dilution of a hydrolyzed protein edible insecticide bait for control of tropical fruit flies (Tephritidae). The bait, commercially marketed as GF-120, is a mixture of the insecticide spinosad, a microbially hydrolyzed protein, sugars, adjuvants and a series of conditioners. Bait is formulated to have both an attractant and feeding stimulant function. In experiments to determine the maximum persistence of the commercial formulation we found that if bait is protected from rain but exposed to other environmental factors (heat, sunlight, humidity) the bait remained effective for about 14 days in field cages. In a laboratory cage test experiment to determine the effects of spinosad concentration in the commercial bait after exposure to field conditions, concentrations of 8 mg AI l−1 bait did not differ from the control (no spinosad). Concentrations of 80 mg l−1 had significantly lower knockdown (kill flies within 2 h) than 800 mg l−1, but the two concentrations did not significantly differ in numbers of survivors over a 4 day treatment period time. Field cage tests showed significant differences among spinosad concentrations and bait ages for knockdown of flies but 80 and 800 mg spinosad l−1 were similar for rates of survival over 4 day tests. A final test was performed to measure the effects of bait+insecticide dilution on function of the bait after 14 days aging in the field cage. Results showed that a four-fold dilution of the complete bait did not significantly reduce attraction or knockdown. The undiluted bait was superior to eight-fold dilution but did not differ from four-fold dilution.
From 20 August to 19 September 1993 and 1994, we assessed the effects of treating ripening sunflower fields with DRC-1339-treated rice baits on blackbird (Icterinae) damage to sunflower fields found within ⩽ 3.2 km of blackbird roosts. The number of blackbirds () using roosts centered within the treated and untreated test areas were similar (P = 0.432). The number of blackbirds using sunflower fields in the test areas did not vary among days after treatment (P = 0.538) or between treated and untreated areas (P = 0.203, averaging 3203 ± 361). The percentage of sunflower damage did not differ (P = 0.736) between treatments (). It appears broadcasting DRC-1339-treated rice baits in ripening sunflower fields does not reduce local blackbird populations or sunflower damage.
[14C]Cymoxanil was applied to either the root system or to the foliage of tomato plants and its uptake, translocation and degradation was followed using autoradiography, combustion and thin-layer chromatographic analyses of water or methanolic extracts. Cymoxanil was taken up by the root system within 1 h and translocated to cotyledons, stem and leaves within 16 h. The compound was degraded, mostly to glycine, within 16–44 h, in the root and all parts of the shoot. When applied to the surface of leaf 2 of five-leaf plants, enhanced uptake, translocation and degradation (mainly to glycine) of [14C]cymoxanil was observed in plants treated with a mixture of oxadixyl and [14C]cymoxanil, compared with plants treated with [14C]cymoxanil alone. Root application data confirm that cymoxanil is a systemic compound with a short persistance in tomato plants. Foliage application data suggest that the well-documented synergistic interaction between cymoxanil, oxadixyl and mancozeb in controlling plant diseases caused by Peronosporales does not result from a delayed degradation of cymoxanil in the presence of the other fungicides; the mechanism of synergism has not yet been elucidated.
Systematic rat control was developed in oil palm plantations in the 1960s and 1970s by comparing bait mixtures and application techniques mainly for anticoagulant poisons, in trials with related ecological studies. Rattus tiomanicus populations of 100–600/ha were estimated in plantings of a range of ages and localities, and numbers fluctuated slowly within these limits in a single plot without control, monitored over 20 years. Optimum control was with maize based wax-bound baits (ca. 12 g), applied one per palm (generally 114–138/ha) with “replacement rounds” of those taken, at 4-day intervals until acceptance declined below 20% (usually about 5 or 6 rounds), doing large areas at 6-month intervals to minimise intermediate build up. Potential losses are estimated at 5–10% of the palm oil product, worth, within the wide price limits of recent years, from $(US)48 to 288/ha. Baiting cost is around $15/ha. Events since 1982 include appearance of warfarin resistant populations (but “second generation” anticoagulants remain effective); the replacement of the formerly ubiquitous and virtually sole rat of mature oil palms, R. tiomanicus, by R. rattus diardii, in several localities; and some populations displaying non-acceptance of baits.
Fungicides are routinely used to prevent yield losses in winter wheat in southern Sweden. Yield and 1000 grain weight (TGW) data from 432 trials in farmers' fields were evaluated to review long-term yields (1977–2005) and control of eyespot and Leaf Blotch Diseases (LBDs, including Septoria tritici blotch, Stagonospora nodorum blotch and tan spot), powdery mildew, brown rust and yellow rust. Regression analyses revealed that control of LBDs explained 74% of the yield increase achieved by fungicide treatment at GS 45–61, followed by powdery mildew (20%), brown rust (5%) and yellow rust (1%). Yield of both untreated and fungicide-treated plots increased from approx. 6000 to 12 000 kg ha−1 over the period 1983–2005. Single eyespot treatment improved yield by ∼320 kg ha−1 yr−1 during the period 1977–2002, mainly due to occasional years with severe eyespot. Single leaf disease treatment at GS 45–61 increased mean yield by 10.3% or 810 kg ha−1 yr−1 (9.9% or 660 kg ha−1 yr−1 for 1983–1994 and 10.7% or 970 kg ha−1 yr−1 for 1995–2005) due to increased TGW and grain numbers, especially in high-yielding stands. Additional extra early treatment at GS 30–40 against LBDs increased yield by ∼250 kg ha−1 yr−1. Estimated variance in yield and TGW was higher between years than within years, while that in yield increase and plant diseases was lower between years than within. The results confirm potential and limits of fungicides and the need for supervised control strategies including factors affecting disease, yield and interactions.
Suspected cases of poisoning of honeybees by agricultural pesticides are investigated by the Ministry of Agriculture, Fisheries and Food (in England and Wales) and the Scottish Office Agriculture and Fisheries Department (in Scotland). Studies include field visits to sites where bee mortality is recorded, examination of dead bees for disease, and analysis for the presence of pesticide residues. This paper reviews the results of these investigations for the period 1981–1991. Pesticide poisoning is diagnosed from the detection of residues in dead bees, through interpretation in relation to the median lethal dose (LD50), and ‘subsequent residue level’ (SRL) determined from laboratory studies in which bees were exposed to one LD50 dose. Overall, an annual average of 50 incidents were confirmed as due to pesticide poisoning, involving 30 pesticide active ingredients during the 1981–1991 period. In England and Wales, the principal hazards were caused by misuse of the insecticide triazophos on oilseed rape, a problem that has been reduced to low levels during the 1980s, and by dimethoate use on a variety of arable crops. In Scotland there were fewer incidents, most of which were associated with use of fenitrothion on raspberries, and gamma-HCH on oilseed rape. Opportunities for reducing the risks of poisoning, and for refining the investigation of suspected incidents, are discussed.
Weather factors are driving forces in plant disease development and differ between years and locations. Results from long-term fungicide field trials 1983–2007 and disease surveys 1988–2007 in winter wheat in southern Sweden were used to evaluate relationships between yield, the yield increase obtained by fungicide treatment, thousand grain weight (TGW), disease severity and disease incidence, and the independent variables air temperature and precipitation as monthly means. These two weather variables explained more than 50% of the variation between years regarding yield increase, TGW, LBDs (Leaf Blotch Diseases, including Septoria tritici blotch, Stagonospora nodorum blotch and tan spot), brown rust, yellow rust and eyespot, but less than 50% of the variation in yield and powdery mildew. Precipitation in May was the factor most consistently related to LBD disease intensity, and adding another two weather factors further improved the degree of explanation. Weather factors in the preceding growing season influenced growth stage, powdery mildew and brown rust. Mild winters and springs favoured the biotrophs such as powdery mildew, brown rust and yellow rust. Statistically significant correlations between incidence and severity were found for LBDs, brown rust and eyespot, but not for yellow rust and powdery mildew. Regression models with disease incidence as dependent variable generally had a higher degree of explanation and lower P-value than models with disease severity as dependent variable. Our results confirm that weather data can be successfully used in wheat disease prediction models.
A survey of aphicide use in winter wheat was carried out in the summer of 1984. The survey of more than 60 000 ha revealed that many crops were treated late, dimethoate was the insecticide most frequently used, tank mixes with fungicides were common, and there were regional differences in spray timing and pesticide usage. An existing model of the economic benefits of spraying against the grain aphid (Sitobion avenae F.) was used in conjunction with aphid population assessments in two counties and aphid population predictions from a model, based on aerial samples of aphids, in a third county. The combination of a wide range in aphid population levels between fields, and economically irrational spraying, often resulted in low profits or financial losses. It is proposed that field-by-field decision-making, initiated by a regional forecast and guided by an accessible advisory system based on variable economic thresholds, would improve the accuracy of the decision-making process of cereal farmers in the UK.
Attempts to direct policy according to scientific findings are hampered by the multidimensionality of the potential impacts of pesticides which may affect consumers, operators, wildlife and the environment. Pesticide risk indices seek to reduce these multidimensional impacts to a single dimension and are increasingly used to understand variation in the hazard inherent in pesticides at the farm, regional and national scale. In this study, we used one such risk index, the Environmental Impact Quotient (EIQ), to estimate the hazard posed by pesticide usage from 1992 to 2002 on four UK grown arable crops (wheat, winter barley, spring barley and oilseed rape).Results are reported for three key indicators of hazard. Firstly, the EIQ which rates a pesticide's hazard profile. Secondly, the Environmental Impact (EI) which is the product of the EIQ rating and data on actual usage of a pesticide at a GB level in a given year, and provides an indication of the overall hazard arising from actual historical use at a national scale. Thirdly, EI per hectare standardises the hazard by dividing total EI in year by the area of crop grown in that year.The results suggest that between 1992 and 2002, the overall hazard posed by the pesticides applied to these crops declined substantially, as evidenced by a 10% decrease in pesticide usage, an 8% increase in yield per hectare, a 14% decrease in overall EIQ rating, a 15% decrease in EI rating and a 7% decrease in EI per hectare. Both Government and the industry may wish to take some encouragement from these trends, which seem to be wholly in line with societal demands of agriculture.
Aerial spray field trials were conducted in 1992 and 1993 to evaluate the feasibility of reducing the dosage of nuclear polyhedrosis virus applied against gypsy moth, Lymantria dispar (L.), larvae from a double application of 5 × 1011 polyhedral inclusion bodies (PIB) ha−1 (total 1012 PIB ha−1) to double applications of 5 × 1010PIB ha−1 (total 1011 PIB ha−1) or single applications of 5 × 1010 or 1011 PIB ha−1. The reduced dosages were applied with a virus enhancer, Blankophor BBH, in conjunction with a wettable powder formulation developed by American Cyanamid Co. Replicated virus treatments were compared to double applications of Bacillus thuringiensis (B.t.) at 50 BIU ha−1 (Foray 76B) in 1992 and 30 BIU ha−1 (Foray 48B) in 1993. In 1992, three double applications of nuclear polyhedrosis virus at 5.0 l ha−1 application−1, 5 × 1011 PIB ha−1 in water with 25% molasses, 6.0% Orzan LS and 2.0% Bond sticker, 5 × 1011 PIB ha−1 American Cyanamid Co. wettable powder and 5 × 1010 PIB ha−1 American Cyanamid Co. wettable powder plus 1.0% Blankophor BBH, were applied to 13 plots with a combined area of 91.1 ha. One B.t. treatment, a double application of Foray 76B at 50 BIU ha−1 in 2.5 1 ha−1, was applied to three plots with a combined area of 37.0 ha, and four plots with a combined area of 62.0 ha were used as untreated check plots. The reduction in egg mass densities in all treatments was considerable and all post-spray counts were less than the treatment target threshold of 1250 ha−1. Egg mass densities for pre-spray and post-spray counts were similar in the untreated check plots. Corrected population reductions (Abbott's formula) for the three virus treatments were 66, 74 and 84%, respectively, and 95% for the Foray 76B treatment. However, defoliation of red oak, Quercus rubra L., and white oak, Q. alba L., was light and there were no significant differences in defoliation of oak trees between the treated and untreated check plots. In 1993, there were three nuclear polyhedrosis virus treatments using the American Cyanamid Co. wettable powder formulation plus 1.0% Blankophor BBH at 5.0 1 ha−1; a double application at 5 × 1010 PIB ha−1 (total 1012 PIB ha−1), a single application at 5 × 1010 PIB ha−1, and a single application at 1011 PIB ha−1, were applied to 15 10-ha plots, and a double application of Foray 48B at 30 BIU in 2.4 l ha−1 was applied to five 10-ha plots. Five untreated 10-ha plots served as checks. Overwinter mortality of eggs caused a major population decline in the area, and egg mass counts in check plots declined by 77%. Nevertheless, all treatments had a significant impact on the gypsy moth population and corrected population reductions were 68, 63 and 61% for the three virus treatments, respectively, and 63% for the Foray 48B treatment. Mean defoliation was 50% in the check plots, but significantly less in all the treatments. In addition to egg mass counts and defoliation estimates, pupae in burlap traps and male moths in pheromone traps were sampled in both the 1992 and 1993 studies and these results are discussed.
MCPA, 2,4-D and their salts, amines or esters have been the most widely used herbicides for many years, especially in cereal crops. They kill broad-leaved plants but not grasses. These phenoxyherbicides have been detected in soil in concentrations reaching 0.63 mg/kg of dry matter. The present work was undertaken in order to study the toxicological effects of commercial preparations: Aminopielik 720 (2,4-D–NH4+ salt, 68% of active ingredient) and Chwastox Extra 300SL (MCPA—Na salt, 30% of active ingredient) on vascular plants. The species tested were the broad-leaved plants Lepidium sativum, Sinapis alba and grasses (cereal plants) Avena sativa, Triticum aestivum. The influence of the commercial products on seed germination and root or shoot growth inhibition of the plants was studied. The tests lasted 168 h. Comparison of the IC50 values for the seed germination and shoot growth inhibition of grasses and broad-leaved plants showed great differences. IC50 values obtained for L. sativum and S. alba were in some cases nearly 100 times lower than the IC50 values for A. sativa and T. aestivum (both in seed germination and shoot inhibition tests). In the case of root growth inhibition, the differences between IC50 values for broad-leaved plants and grasses were less significant for Chwastox Extra. The IC50 values for germination were very high (ranged from 104 to 6704 mga.i. l−1), but for shoot (S) or root (R) growth inhibition they were lower and ranged from 0.15 to 73 mga.i. l−1 (S) and from 0.07 to 12 mga.i. l−1 (R) for broad-leaved plants and grasses, respectively. Thus phenoxyacetic herbicides have been found to inhibit root and shoot growth for both broad-leaved plants and grasses.
Four European countries on a north to south trajectory were sampled for their crop protection policies. Selected respondents were interviewed about their expectations with respect to the eventual reduction of pesticide use in the near future. Crop protection, policies among these countries are out of phase: Sweden has successfully completed a plan to reduce pesticide usage to 50% of a base-line value; the Netherlands are in the process of implementing such a plan; France is aiming to achieve supervised control; Spain is trying to reduce pesticide residues in export commodities. Before the year 2000, considerable reductions in the volume of pesticides used can be expected only in the Netherlands. Among the reasons for scepticism with regard to the reduction of dependence on pesticides and pesticide use are ‘lack of alternatives’, ‘inadequate research capacity’, ‘inadequate supervision for observance of regulations’, ‘absence of clear national policies’ and ‘absence of EC policy’.
Jalali, S.K., Mohan, K.S., Singh, S.P., Manjunath, T.M. and Lalitha, Y., 2004. Baseline-susceptibility of the old-world bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) populations from India to Bacillus thuringiensis Cry1 Ac insecticidal protein. Crop Protection, 23 (1): 53-59, January 2004.
The baseline-susceptibility of Indian populations of Helicoverpa armigera (Hübner) to the insecticidal protein Cry1Ac, from Bacillus thuringiensis (Berliner) was determined through bioassays conducted in 1999 and 2001. Populations of H. armigera were collected from cotton fields of nine major cotton growing states in India, which included (field locations in parentheses) Punjab (Bathinda), Haryana (Sirsa), Rajasthan (Sriganganagar), Madhya Pradesh (Barwah and Khandwa), Gujarat (Rajkot, Vadodra and Anand), Maharashtra (Jalgoan, Jalna, Akola and Yavatmal), Andhra Pradesh (Adilabad, Warangal, Khammam and Guntur), Karnataka (Raichur, Davangere and Ranebennur) and Tamil Nadu (Coimbatore and Dindigul). All populations were susceptible to Cry1Ac. The mean lethal concentrations, LC50—ranged from 0.14 to 0.71 and from 0.11 to 0.61; LC90 ranged from 1.17 to 6.94 and from 1.02 to 6.70 μg of Cry1Ac / ml of diet in 1999 and 2001 populations, respectively. Similarly, moult inhibitory concentrations, MIC50—ranged from 0.05 to 0.27 and from 0.05 to 0.14; MIC90—values ranged from 0.33 to 1.58 and from 0.25 to 0.91 μg of Cry1Ac in 1999 and 2001 populations, respectively. The effective concentrations (weight stunting related) EC50 ranged from 0.003 to 0.008 and from 0.0003 to 0.004; EC90 ranged from 0.029 to 0.076 and from 0.009 to 0.054 μg of Cry1Ac in 1999 and 2001 populations, respectively. These values form the baseline data for susceptibility of H. armigera to Cry1Ac and can be used as benchmarks for monitoring resistance to Cry1Ac. Bt cotton, expressing Cry1Ac, was approved for commercial cultivation in India in 2002.
CGA 219417 (proposed common name: cyprodinil) is a pyrimidinamine currently being developed as a foliar fungicide for cereals, grapes, vegetable crops and deciduous fruit. It has a new mode of action and shows no cross-resistance to any current market product. On cereals, CGA 219417 exhibits a broad fungicidal spectrum with good activity against Pseudocercosporella herpotrichoides, Erysiphe graminis, Pyrenophora teres, Rhynchosporium secalis and Septoria nodorum on ears. The strength of CGA 219417 on grapes, vegetable crops and strawberries is its excellent activity against Botrytis spp. On deciduous fruit the key target pathogen genera are Venturia, Alternaria and Monilinia spp. The fungicide has excellent safety for users, consumers and environment. In addition, its other characteristics, such as not being harmful to beneficial organisms, make it a promising product for flexible integrated disease-control practices.
The last quarter of the 20th century has seen the withdrawal of many compounds formerly used as fumigants. Methyl bromide, the fumigant with the widest range of applications is scheduled for worldwide withdrawal from routine use as a fumigant in 2015 under the directive of the Montreal Protocol on ozone-depleting substances. Phosphine, the only other commodity fumigant available worldwide, used principally on bulk grain but also on dried fruit, nuts, cocoa, coffee and bagged rice, is currently under regulatory review in the USA and Europe. The prospects for the continued use of fumigants to protect plant and animal health and commodity trading are discussed in the context of mounting pressures on compounds due to registration requirements, atmospheric emission controls, fears on safety or health grounds, the incidence of resistance, and the need to achieve increasingly high standards of pest control in international trade. Some recent research results relating to fumigant toxicity and gas application technology are presented which indicate ways in which the use of some of the few remaining fumigants can be extended in the 21st century.
Efficacy of the non-steroidal ecdysone agonist, RH-2485, was determined on Helicoverpa armigera larvae under laboratory and field conditions. RH-2485 sprays (25–150 μg/ml) caused premature, incomplete molting in 28–94% of the treated 2nd instar larvae within 24 h. Topical application of RH-2485 to 6th instar larvae (30–200 ng/larva), caused premature molting in 3-83% within 24 h, and 66–96% in 15 days, post-treatment. The eD10, eD50 and eD90 for 24 h were determined as 37, 100 and 250 ng/larva, and for 15 days as 0.65, 7.50 and 100 ng/larva, respectively, according to the corrected trend line. Ingestion of 0.1–1000 ng RH-2485 by 6th instars caused premature molting in 10–65% of the larvae in 24 h and 8–64% in 15 days. Field trials indicated that RH-2485 sprays at 50–150 g (AI)/ha decreased the larval population of boll worms by 68–73%. Correspondingly, the injury by the pest to bolls and apical buds of the cotton plants was decreased by 54–65% and 57–77%, respectively.
Several plant viruses are highly contagious and their effects on plants are often drastic. Many seriously reduce crop yield and quality. Numerous disorders are caused or triggered by viruses and a great deal of money is spent on preventing virus diseases from becoming disastrous. Losses caused by any disease cannot be measured directly because potential yield and damage are so variable. Experimental assessment of the losses attributable to virus diseases is particularly difficult because it is extremely hard to prevent contamination of healthy control plants and inoculation under vector-proof conditions may not reflect accurately what happens under natural conditions. The prevalence of the causal viruses or the extent of attack are not reliable guides to the amount of damage caused; this contrasts with the situation with invertebrate pests where losses are usually related to the population densities of the pests. In a few virus diseases, attempts have been made to establish the relationships between final yield loss and certain indicators such as incidence, severity and duration of disease, or between combinations of these, but the relationships seem to be valid only under strictly defined conditions. The main aims of this work have been to estimate actual losses inflicted on a farmer's crop or upon a larger area, to predict the magnitude of losses that may develop and to decide what control measures are justified. In practice, assessment of loss has been extrapolated from trials in which various infection severities and infection times have been used to simulate natural situations. Yield improvements with virus-free propagation material have sometimes been used for loss assessment. Losses caused by virus diseases depend on the cultivar involved: evaluation of the resistance of different cultivars may be further improved by assessing the effects of viruses on yield rather than by assessing the severity of symptoms. Losses is strictly financial terms are influenced by fluctuating prices for crop products and are even more difficult to asses, let alone to predict, than are losses of yield. Nevertheless, a better understanding of the way in which virus disease epidemics develop, and of the resulting biological and economic losses, is essential for effective crop protection, whether on individual farms or on a national scale.