Acknowledgments 



This work was supported by a grant from the 

 Washington Tree Fruit Research Commission and 



USDA SEA CSREES grant # 97-34365-5043. We 

 thank Gary Puterka of the USDA Regional Fruit 

 lab in Kearneysville, WV for providing the sugar 

 ester. 



^C •'k *C *C *C 



Fate of Apple Maggot Flies Alighting on 

 Pesticide-treated Spheres in a Commercial 

 Apple Orchard 



Xingping Hu, Eric Gemborys, Max Prokopy, and Ronald Prokopy 

 Department of Entomology, University of Massachusetts 



As mentioned in the preceding article, unusu- 

 ally large numbers of apple maggot flies (AMF) 

 invaded certain commercial apple orchards in 

 Massachusetts in 1998. In most cases, invasion 

 was attributable to a combination of large num- 

 bers of AMF emerging from overwintered pupae 

 beneath unmanaged apple trees nearby commer- 

 cial orchards and to near or total absence of any 

 fruit on such unmanaged trees, leading to AMF 

 abandonment of unmanaged trees and movement 

 to fruiting trees in commercial orchards. We took 

 advantage of this situation in a cooperating orchard 

 and studied the fate of AMF that were observed to 

 alight on pesticide-treated red spheres. 



Methods & Materials 



Eight wooden spheres, 3 inches in diameter, 

 were coated with a mixture containing 2% active 

 ingredient of imidacloprid (Merit 75 WP), 20% 

 sucrose, and 78% Glidden Red Latex Gloss Enamel 

 paint. Four similar spheres, serving as non-toxi- 



cant checks, received only the sucrose and paint. 

 All of the spheres were exposed outdoors for 3 

 weeks before testing (but no rain fell during this 

 period). On three sunny days (July 21, 27, and 

 29), each of three observers hung two pesticide- 

 treated and one check sphere about 2 feet apart in 

 an apple tree and watched each sphere continu- 

 ously for alighting AMF for a period of about 6 

 hours per day. An attempt was made to capture 

 each AMF after it departed or fell from a sphere. 

 Captured AMF were placed singly in small clean 

 cups, supplied with food and water, and observed 

 1, 24, and 72 hours later for mortality. 



Results 



In all, 36 AMF were observed alighting on pes- 

 ticide-treated spheres and 19 AMF on untreated 

 check spheres. Of the 36 alighting on pesticide- 

 treated spheres, the median duration of stay was 

 about 3 minutes and 25 died while still on a sphere 

 or within 1 hour after having fallen from a sphere. 



10 



Fruit Notes, Volume 63 (Number 4), Fall, 1998 



