Effects of floral resources on fitness of the parasitoids Trichogramma exiguum (Hymenoptera: Trichogrammatidae) and Cotesia congregata (Hymenoptera: Braconidae)
ABSTRACT This study was conducted to determine if floral resources enhanced longevity and fecundity of the egg parasitoid Trichogramma exiguum Pinto & Platner and longevity of the larval parasitoid Cotesia congregata (Say). Newly eclosed (⩽12 h) female wasps were provisioned with fennel (Foeniculum vulgare P. Mill.) or buckwheat (Fagopyrum esculentum Moench) flowers or one of two controls: honey or water. Wasps were monitored daily until all had died. Daily egg production by T. exiguum was monitored using Ephestia kuehniella Keller egg cards. Longevity of both T. exiguum (6.7 d) and C. congregata (5.1 d) provided buckwheat flowers was increased approximately 8.5-fold compared with wasps provided only water. Buckwheat-provisioned T. exiguum exhibited 2-fold greater longevity than those provided fennel. Longevity of C. congregata provisioned with fennel and honey was not statistically different. Water-provisioned T. exiguum and C. congregata exhibited the shortest longevity (0.8 and 0.6 d, respectively). Total fecundity was 6.3-fold greater in T. exiguum provisioned with buckwheat and 2.3-fold greater in T. exiguum provisioned with fennel than in water controls. Average female to male ratio of progeny over the lifetime of each female was significantly greatest in T. exiguum provisioned with water alone, likely because of sperm depletion in wasps exhibiting greater longevity. Total mean number of female offspring produced was significantly greatest in T. exiguum provided honey or buckwheat flowers although no difference in total female offspring were observed between adults provisioned with buckwheat or fennel flowers. Our results show that provisioning T. exiguum with honey and buckwheat flowers resulted in greater longevity, total fecundity, and lifetime production of female offspring than water alone. Buckwheat flowers also lead to greater longevity in C. congregata.
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ABSTRACT: Habitat management is an important element in sustainable agriculture and can be used to maximize a range of ecosystem services that support crop production. An important example of such ecosystem services is biological control of pests which can be enhanced by providing arthropod natural enemies with suitable floral resources. The potential risk of this approach, however, is that flowering plants may enhance the fitness of the targeted pests as well. We conducted experiments to identify selective plant species that would improve the longevity and parasitization rate of the parasitoid wasp Microplitis mediator without benefiting its host pest, the cabbage moth Mamestra brassicae. Effects on longevity were also assessed for Diadegma fenestrale, a generalist parasitoid wasp attacking Lepidopteran pests. Additionally, we compared the effects of floral and extrafloral nectar, the latter being formed in some plant species and can significantly prolong the duration of nectar availability for natural enemies. Longevity of M. mediator and D. fenestrale as well as parasitization rates of M. mediator was significantly increased by the presence of Fagopyrum esculentum (floral nectar), Centaurea cyanus (floral and extrafloral nectar) and non-flowering Vicia sativa (extrafloral nectar). M. mediator parasitized 202.3±29.7 M. brassicae larvae during its lifetime when presented F. esculentum, compared to 14.4±3.4 larvae in the absence of floral resources. Extrafloral nectar of C. cyanus and V. sativa was as suitable for M. mediator as floral nectar and significantly increased longevity and parasitization rates. Longevity and fecundity of M. brassicae were not supported by the plant species tested. These results stress the importance of plant screening to achieve plant selectivity and to maximize biological control. F. esculentum, C. cyanus and V. sativa are recommended as selective plant species to enhance parasitoids of M. brassicae.Basic and Applied Ecology 02/2012; · 2.39 Impact Factor
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ABSTRACT: Parasitoid adults can directly feed on floral nectar and honeydew containing monosaccharides and disaccharides. Oligosaccharides such as maltose, melezitose and raffinose are also found in honeydew but are rare in floral nectar. The effects of six different sugar resources on the longevity, fecundity and nutrient reserves of Microplitis mediator, a larval endoparasitoid in the cotton bollworm Helicoverpa armigera (Hübner) were determined in our laboratory. The results showed that both food and sex affected longevity of this wasp. Females and males of M. mediator fed with 1M sucrose solution survived longer than controls fed with water (5.7- and 3.7-fold longer, respectively). When provided with sucrose, glucose or fructose solutions, the parasitoid generated 3.6- to 3.7-fold more offspring than controls, and 60–75% of these progenies were produced during the first 5days. When separately given fructose, sucrose or glucose, this wasp accumulated fructose and total sugar at the highest level, which means a high sugar levels might lead to prolonging longevity and more offspring in M. mediator. In addition, compared with organisms fed galactose or raffinose, M. mediator fed sucrose or fructose accumulated high glycogen levels. Furthermore, in M. mediator, the lipid content declined with the advancing age. Females showed the slowest lipid metabolic rates when fed with sucrose, glucose, fructose, mannose and galactose solutions versus when fed with raffinose and control. In addition, only sucrose had a significant effect on lipid levels in males nearing the end of life.Biological Control 01/2010; 52(1):51-57. · 1.87 Impact Factor
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ABSTRACT: 1 The rice leaffolder Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae) is a serious rice pest in Asia. The conspicuous foliar damage caused by C. medinalis larvae leads to early‐season insecticide applications that disrupt the biological control of this and other pest species. 2 Despite the often dramatic impact of C. medinalis, rice plants can tolerate severe defoliation with no impact on grain yield, although persuading farmers to withhold insecticide application has proven very difficult. 3 The present review assesses the prevention of damage caused by C. medinalis via biological control using parasitoids. Information on the indigenous parasitoids of C. medinalis is drawn together for the first time from the non‐English literature published in Asia. This is integrated with the wider English language literature to provide a comprehensive analysis of the parasitoid fauna. 4 Survey studies have been conducted in many Asian countries in recent decades, showing that parasitoids of rice pests can achieve high rates of parasitism but are far from consistent as a mortality factor. There is much less work available on the biology of leaffolder parasitoids in rice and there is an unexpected dearth of studies regarding increasing their performance by providing nectar sources, which is a widely explored approach for other crop systems. 5 It is concluded that the recently reported work in which nectar plants are established on rice bunds to support planthopper parasitoids may have significant benefit for leaffolder parasitoids. The use of plant species, however, that are selective in not allowing adult moths to feed will be essential.Agricultural and Forest Entomology 02/2012; 14(1). · 1.56 Impact Factor