Rosy apple aphid, Dysaphis plantaginea, can be an important pest on apple trees in the East and Midwest. Previous research using green lacewing or predatory midge releases for control of other aphid species had given contradictory results. The impact of augmentative releases of larvae and eggs of the lady beetle Adalia bipunctata against rosy apple aphid was assessed in Swiss orchards in 1997.
Lady beetle eggs and second instar larvae were released at two different times in spring on 3-year old artificially infested or 20-year old naturally infested apple trees.
Eggs are easier to handle and less expensive to rear than larvae, but were less reliable for releases. Some early releases did not hatch, probably because of poor weather conditions.
Larval releases had a strong impact on the numbers of rosy apple aphids, particularly when predator-prey ratios were 1:1 and 5:1, but not at lower ratios. Early releases prevented the build-up of rosy apple aphid colonies. The larvae were very efficient just before apple flowering, which is when growers normally spray their trees for this pest.
Lady beetle larvae were much less efficient on trees where ants that protect the aphids were present. There were 30% more aphids on ant-attended trees than on ant-free ones. However, ants were not as active before bloom--the critical period to suppress aphid populations.
Although A. bipunctata develops and is active early in the spring, naturally occurring populations usually fail to control aphid populations because they develop a lot slower than their prey. Supplementing the lady beetle larval population can provide control of rosy apple aphid.
Wyss, E., M. Villiger, J. L. Hemptinne, and H. Muller-Scharer. 1999. Effects of augmentative releases of eggs and larvae of the ladybird beetle, Adalia bipunctata, on the abundance of the rosy apple aphid, Dysaphis plantaginea, in organic apple orchards. Ent. Exp. Appl. 90(2):167-173.
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