in local orchards to assure successful control. One of the aims 

 of our apple pest management program is reduction in spray appli- 

 cations without increased aphid injury. To achieve this aim, we 

 are hopeful that aphid natural enemies will play a greater role in 

 aphid control than they now do. 



The most frequently reported natural enemies of aphids are 

 lady beetles, lacewing larvae, syrphid fly larvae, and anthocorid 

 bugs. However, while studying the natural enemy complex of the 

 apple aphid in a Western Massachusetts apple orchard, we found 

 quite a different species to be the dominant predator: the larval 

 stage of a cecidomyiid midge by the name of Aphidoletes aphidimyza . 



The adult midge is a small delicate, fly-like insect which can 

 lay up to 100 eggs in aphid colonies. The eggs are tiny and orange, 

 resembling particles of paprika. They hatch into larvae in about 

 3 days. The larvae are small (about 1/10 inch long), bright orange 

 colored maggots that feed on many species of aphids. Larval devel- 

 opment is completed in 7 to 10 days, at which time they drop to the 

 soil to form cocoons. The complete life cycle from egg to adult 

 usually takes about 3 weeks. The species overwinters in the soil 

 as a larva within a cocoon. 



Population densities of the apple aphid and its natural enemies 

 were recorded from 1974 through 1976 in an unsprayed section of an 

 apple orchard at the Belchertown Fruit Research Center. Throughout 

 the study period, the cecidomyiid was by far the most abundant pred- 

 ator found. A total of 1902 individuals appeared on sampled foli- 

 age. Syrphids were next most common, with 177 individuals found. 

 Lacewing larvae, lady beetles, and anthocorids appeared only occa- 

 sionally. 



The cecidomyiid was responsible for high apple aphid mortality 

 and dramatic aphid population reductions. Apple terminals were 

 caged with various aphid to cecidomyiid density ratios to study 

 the feeding behavior of the larvae. In every case, those aphid 

 colonies caged with cecidomyiids were either reduced or decimated 

 within 12 days. The overall mean number of aphids killed per ceci- 

 domyiid during its larval development was 28, ranging from 4 to 65, 

 depending on predator and prey abundance. During feeding, cecido- 

 myiid larvae paralyze aphids by injecting salivary toxins. Since 

 there is no struggle by the aphid, killed aphids appear as shriv- 

 elled, blackish bodies with the mouthparts still anchored in the 

 leaf. 



Our studies showed that predaceous cecidomyiids appear in 

 Western Massachusetts apple orchards in mid-June. However, by early 



June, apple aphid populations have already reached injurious levels 



