Aphid Honeydew Increases Alfalfa Weevil Parasitoid Longevity
The ability of parasitoids to attack their hosts may be influenced by the availability of adult food sources such as flower nectar or honeydew from aphids or other insects. To test this idea, England & Evans (1997) studied the influence of honeydew from pea aphids on the longevity and egg production of Bathyplectes curculionis, an imported ichneumonid wasp, which attacks alfalfa weevil larvae. In laboratory studies, adult wasps caged with alfalfa infested with pea aphids fed on the aphid honeydew and lived ~50% longer than wasps caged on alfalfa alone. In another experiment, newly emerged unmated B. curculionis wasps were fed for 2 days on aphid honeydew, sucrose dissolved in water, or just water. Wasps were dissected and the number of eggs produced was counted. Egg production was significantly greater (11-15% increase) when wasps fed on aphid honeydew or sucrose dissolved in water, than when wasps only had access to water.
These results suggest that the availability of pea aphid honeydew in alfalfa fields may increase the longevity and fecundity of B. curculionis. Thus the presence of moderate levels of pea aphids may be beneficial for biological control of alfalfa weevils. Other studies have shown that aphid honeydew may be most important to wasp parasitoids when flower nectar is not available, e.g., early spring or late autumn, depending on the flowering period of local plants.
S. England & E. W. Evans. 1997. Effects of pea aphid honeydew on longevity and fecundity of the alfalfa weevil parasitoid, Bathyplectes curculionis. Environ. Entomol. 26:1437- 1441.
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