in some orchards. Therefore, despite control of summer apple aphid 

 populations by the cecidomyiid, it appears too late in the season 

 to prevent damage due to early-season aphid activities. 



Why don't cecidomyiids appear until mid- June? Where do they 

 overwinter - within or outside the orchard? To find answers to 

 these questions, emergence cage studies were conducted during the 

 spring of 1976. Tent-like cages, containing yellow sticky traps 

 used to capture emerging cecidomyiid adults, were placed in the 

 Belchertown orchard under leaves which harbored cecidomyiid larvae 

 the previous fall. On June 11, 4 cecidomyiid adults were captured 

 within such cages. Thus, a portion, if not the majority, of the 

 cecidomyiid population overwintered within the apple orchard, but 

 adults did not emerge until mid-June. This last finding agrees 

 with the observed first appearance of cecidomyiid eggs on foliage 

 sampled in previous years. Therefore, due to the lack of biologi- 

 cal synchrony between predator and prey, the cecidomyiid is unable 

 to prevent early season aphid damage. The cecidomyiid is still in 

 the soil in the cocoon stage while early damage is occurring. 



For season-long control, apple aphid populations need to be 

 maintained below economic threshold levels until the cecidomyiid 

 predator arrives to control summer aphid populations. We believe 

 that the economic threshold level of the apple aphid (that is, the 

 point at which some remedial action should be taken) is approxi- 

 mately 50 apple aphids per terminal leaf. 



Drs. Madsen, Peters, and Vakenti of the Summerland Research 

 Station in British Columbia were able to reduce the number of sprays 

 needed to obtain apple aphid control by monitoring aphid populations, 

 Their results are presented in an article entitled "Pest Management: 



Experience in Six British Columbia Apple Orchards," which appeared 

 in the August, 1975 issue of the Canadian Entomologist . Sprays 

 were recommended when 50 per cent of the leaves sampled were aphid 

 infested. 



Pesticide sprays have been shoi\m to have a detrimental effect 

 on many natural enemies of pests. For example, syrphid flies are 

 abundant in late May and June in many commercial orchards. They 

 lay oval, white eggs about 1/16 of an inch long on apple foliage 

 in or near aphid colonies. The eggs hatch into grayish-white larvae 

 which are ferocious aphid predators. However, syrphids are often 

 though not always, killed by pesticide sprays. Further studies 

 are needed to determine which materials allow syrphid survival. 



We are currently in the process of studying the toxicity of 

 orchard pesticides to the predaceous cecidomyiid to determine its 

 susceptibility, tolerance, or resistance to some of the more recom- 

 mended materials. Cecidomyiid eggs collected from the Belchertown 

 orchard were placed on adhesive tape affixed to glass slides. The 



