Apple Maggot Fly Ovipositional 

 Preferences for Fruit of Different 

 Apple Cultivars 



Juan Rull and Ronald Prokopy 



Department of Entomology, University^ of Massachusetts 



To determine AMF ovipositional preferences, each 

 culti var was assigned a rank from 1 to 12, with 1 being 

 the highest rank and 1 2 the lowest. The cultivar havmg 

 the largest proportion of apples accepted for oviposition 

 in a given seasonal period in a given year received the 

 highest rank. We then averaged cultivar ranks across 

 years and compared cultivar acceptance using 

 appropriate statistical methods. 



Results 



Average ovipositional preference ranks of cultivars 

 at different seasonal periods are shown in Table 1. 

 During early season, the earliest ripening cultivars 

 (Tidemann Red and Vista Bella) ranked significantly 

 higher than some mid-ripening (Gala) and all late- 

 ripening cultivars. During mid-season, early-ripening 

 cultivars that maintained a high flesh firmness (Akane, 

 Tidemann Red, and Jersey Mac) and two mid-ripening 

 cultivars (Gala and Mcintosh) received significantly 

 higher ranks than late-ripening cultivars of Delicious, 

 Fuji, and Golden Delicious and an early ripening 

 cultivar that had become too soft (Vista Bella). During 

 late season, all three mid-ripening cultivars were 

 preferred over all four late-ripening cultivars, despite 

 the fact that some of the late-ripening cultivars had 

 acquired a high sugar content and moderate pulp 

 firmness. 



Discussion 



During early season, AMF preferred to oviposit in 

 sweeter and softer fruit of early cultivars such as 

 Tidemann Red and Vista Bella than in fruit of other 

 cultivars. During mid season, AMF continued to prefer 

 to oviposit in fruit of early cultivars that had not become 

 too soft. Early cultivars ripening slightly later (Jersey 



In the preceding article, we reported on apple 

 maggot fly (AMF) preferences among 13 different 

 cultivars of apple. Preference for different cultivars 

 was established by determining which cultivars 

 accumulated the most AMF on traps placed on trees of 

 different cultivars in six commercial orchards over four 

 years. 



Because cultivar susceptibility is the result of both 

 the degree to which AMF are attracted to apple trees 

 of different cultivars and their propensity to lay eggs 

 in the fruit they find on trees of those cultivars, we 

 decided to evaluate AMF ovipositional preferences for 

 fruit of 12 of the 13 cultivars of apples that were 

 evaluated in our previously reported field experiment. 



Combined results of both studies were employed 

 to establish overall ranking of cultivar susceptibility 

 to AMF. 



Materials & Methods 



AMF ovipositional preferences among five early- 

 ripening cultivars (Akane, Jersey Mac, Paula Red, 

 Tidemann Red, and Vista Bella), three mid-ripening 

 cultivars (Cortland, Gala, and Mcintosh), and four late- 

 ripening cultivars (Braebum, Fuji, Golden Delicious, 

 and Delicious) were examined. Apples were picked 

 from trees in six commercial orchards on a weekly basis 

 during the growing season (early July to early October) 

 over a 4-year period. 



A single apple of each of 12 cultivars was then 

 washed to remove pesticide residue and placed in a 

 30x30x30 cm Plexiglas cage along with 5-10 mature 

 AMF females. Apples were left in cages for a period 

 of 24-48 hours, after which they were examined for 

 oviposition stings under a microscope. Sugar content 

 of apples was determined with a hand refractometer, 

 and pulp firmness was measured with a penetrometer. 



22 



Fruit Notes, Volume 66, 2001 



