Effects of Fruit Ripening, Cultivar, 

 and Storage on Apple Maggot 

 Larval Survival 



Susan L. Butkewich and Ronald J. Prokopy 

 Department of Entomology, University of Massachusetts 



Under current practice, the times of year 

 when apple maggot flies (AMF) begin and cease 

 laying eggs in commercial apple orchards define 

 the period during which control measures are 

 used against the flies. Conceivably, however, 

 the larvae that hatch from AMF eggs are not 

 able to develop and tunnel into fruit equally well 

 across all fruit ripening periods or cultivars. In 

 fact, Reissig (1979) in western New York found 

 that survival of AMF larvae in apples varied 

 considerably with cultivar and infestation date. 

 For example, when apples were infested from 

 June 25 to July 15 and were picked September 

 7, the percentage of apples producing larvae was 

 32% in Wealthy, 12% in Mcintosh, 8% in Rhode 

 Island Greening, and 4% in Rome. When apples 

 were infested from August 16 to September 6 

 and again picked on September 7, the percent- 

 age producing larvae increased drastically to 

 89% in Wealthy, 59% in Mcintosh, 35% in Rhode 

 Island Greening, and 48% in Rome. These 

 findings suggest that early-season control of 

 AMF, especially on late ripening cultivars, may 

 be somewhat less important than mid- or late- 

 season control. 



To determine how well the findings of 

 Reissig in western New York might apply to 

 Massachusetts conditions, we carried out two 

 experiments at the Horticultural Research Cen- 

 ter in Belchertown, MA Besides examining 

 AMF larval survival at different egg infestation 

 dates and for different cultivars, we also studied 

 larval survival under different fruit storage re- 

 gimes. 



Methods Used 



In both experiments, trees on M.7 rootstock 

 were covered with cloth cages beginning in late 

 June (before appearance of any AMF) to protect 

 against unwanted egglaying by wild flies. 



The first experiment involved collecting eggs 

 laid in wax fruit by mated AMF females. Using 

 a small paint brush eggs were inserted into 

 punctures made with a sterilized needle in 

 Mcintosh and Delicious apples. Each apple 

 received five punctures and one egg per punc- 

 ture. Each cultivar received 100 eggs on July 22 

 and 200 eggs on August 20, 1987. Apples were 

 either picked just after artificial infestation or 

 were left on the trees until they fell naturally. In 

 both cases, fruit were kept at 72°F for six weeks, 

 when the percentage of eggs that gave rise to 

 pupae was recorded. 



In the second experiment, a mature female 

 and mature male AMF, together with some food 

 and water, were placed in a cloth cage over a 

 cluster of Mcintosh or Delicious apples for a 

 period of two days to permit egglaying. The 

 numbers of eggs laid varied from fruit to fruit. 

 This procedure was carried out for 25 apples of 

 each cultivar each week from July 18 to August 

 22, 1988. Fruit were allowed to remain on the 

 tree until harvest: September 1 1 (Mcintosh) and 

 October 2 (Delicious). Then apples from each 

 infestation date and cultivar were divided 

 equally into three groups before being examined 

 for larval tunneling. Group one was stored at 

 72°F for six weeks. Group two was stored in a 

 cold room at 38°F for six weeks Group three was 

 examined immediately. Each AMF egglaying 

 sting was scored for larval tunnel depth by 



Fruit Notes, Fall, 1991 



