Cultivar Preferences Affect Apple Maggot 

 Fly Distribution in Orchards 



Juan Rull and Ronald Prokopy 



Department of Entomology, University of Massachusetts 



It has been known for decades that some apple 

 cultivars are more susceptible to apple maggot fly 

 (AMF) damage than others. Whether this is because 

 trees of preferred cultivars attract more AMF than 

 others and/or because the fruit they bear is more 

 acceptable for oviposition than the fruit of less- 

 preferred cultivars is not very clear. In general, it is 

 thought that because fruit of early and mid-ripening 

 cultivars reach a higher sugar content and soften earlier 

 in the season, they are preferred by AMF over late- 

 ripening cultivars (Dean and Chapman, 1973). 

 Determining AMF cultivar preference is important 

 because fly activity in apple orchards could concentrate 

 in areas where preferred cultivars are found, which in 

 turn could affect control measures using traps. 



Here, we report results of a four-year experiment 

 comparing AMF accumulation on unbaited traps among 

 13 apple cultivars grown in Massachusetts. Our 

 objective was to generate cultivar preference 

 information that would allow us to design optimal trap 

 deployment strategies for AMF behavioral control 

 using odor-baited traps. 



Materials & Methods 



We compared AMF preferences among apple 

 cultivars grouped into three phenological categories: 

 early, mid, and late ripening. Within each category, 

 we selected three to six cultivars represented in New 

 England apple orchards. Cultivar comparisons were 

 made over a 4-year period (1997-2000) in six 

 commercial orchards having different cultivar 

 arrangements managed under first-level IPM practices 

 (2-3 summer insecticide sprays against AMF). 



Early-ripening cultivars included Akane, Jersey 

 Mac, Paula Red, Red Astrachan, Tidemann Red, and 

 Vista Bella. Mid-ripening cultivars included Cortland, 

 Gala, and Mcintosh. Late-ripening cultivars included 

 Braebum, Fuji, Golden Delicious, and Delicious. 



Eight medium to large-size trees of each cultivar 

 were selected in each orchard. Each tree received an 

 unbaited red sphere coated with Tangletrap to capture 

 alighting AMF. Spheres were placed on trees in early 

 July and remained on trees until harvest of late cultivars 

 in early October. Traps were inspected once per week, 

 when captured AMF were counted and removed. Each 

 cultivar was ranked in terms of preference by assigning 

 a relative rank from 1 to 13, with 1 being the highest 

 rank and 13 the lowest. The cultivar whose traps 

 accumulated the most AMF received the highest rank. 



Results 



Because cultivar preferences varied along the 

 growing season, we broke capture data into three 

 distinct seasonal periods: early season (early July to 

 early August), mid season (early August to early 

 September), and late season (early September to early 

 October). Average preference ranks among cultivars 

 over the 4-year period reveal that during early season, 

 two early-ripening cultivars ranked highest in terms of 

 AMF preference: Red Astrachan and Tidemann Red 

 (Table 1). These ranked numerically higher than Jersey 

 Mac, Gala, Delicious, Fuji, Vista Bella, and Akane, 

 with all other cultivars having statistically lower ranks. 

 During mid season, Tidemann Red retained its high 

 rank. Red Astrachan and Vista Bella, which had lost 

 firmness and had begun dropping heavily from trees, 

 experienced a dramatic drop in preference. Conversely, 

 Jersey Mac and Akane, both early-ripening cultivars 

 that ripen later than Red Astrachan, gained in average 

 rank. Fuji gained substantially in rank while Gala 

 retained a relatively high rank. During late season. 

 Gala and Fuji were the most preferred cultivars. All 

 late-ripening cultivars gained in rank. By contrast, all 

 early-ripening cultivars (except Red Astrachan) 

 dropped in rank. Paula Red, Jersey Mac, and Vista 

 Bella ranked significantly lower than Gala, Fuji, and 



Fruit Notes. V olume 66. 2001 



19 



