Tnble 2. f-'ornging behavior of .ipplc maggot fly females, subsequent egglaying propensity and 

 percent mortality following feeding on untreated, fipronil-treated or nnidacloprid-treated red 

 wooden spheres. Foraging and cgglaynig behaviors were evaluated I hour after exposure to spheres. 



Treated spheres contained 2% active ingredient of insecticide in latex paint. All spheres were 



subjected to 3 weeks field exposure and then were re-treated with 20% sucrose solution just 



prior to testing. 



Maximum permited feeding time = 600 seconds. 



Flies were placed individually on a small, caged tree. Numbers represent mean foraging time of 



flies capable of foraging. Maximum permitted canopy foragmg time = 900 seconds. 



Immediately after foraging, each fly was exposed to a hawthorn fruit. Maximum permitted time 



on fruit = 600 seconds. 



16% of AMP that were exposed to fipronil-treated 

 spheres attempted to lay an egg. Together, the re- 

 sults of the behavior tests reflect the fact that 

 fipronil is a much slower-acting compound than 

 imidacloprid. AMF mortality following ingestion 

 of fipronil was only about a third the amount at 

 24 hours after exposure as at 72 hours afterward, 

 whereas with imidacloprid, mortality at 24 hours 

 was nearly equal to that at 72 hours (Table 2). 



Conclusions 



Our combined findings show that imidacloprid 

 performed better as an AMF toxicant on pesticide- 

 treated spheres than did any of three other candi- 

 date toxicants tested here: fipronil, spinosad and 

 sugar ester. Imidacloprid at 2% a.i. in Glidden 



Red Latex Gloss Enamel paint gave excellent sea- 

 son-long ( 1 2 weeks) AMF control provided that it 

 was ingested with a feeding stimulant (sucrose). It 

 gave very poor control, as did fipronil, in the ab- 

 sence of sucrose, irrespective of dose used (16% 

 a.i. was the highest dose tested). A low dose of 

 imidacloprid, such as 2% a.i., not only is less ex- 

 pensive than a higher dose but is safer for those 

 handling pesticide-treated spheres. Imidacloprid 

 rapidly immobilized AMF that ingested it, result- 

 ing in very little or no subsequent foraging and 

 egglaying activity of exposed AMF. Because 

 imidacloprid seems to be an ideal toxicant for use 

 in conjunction with sucrose on pesticide-treated 

 spheres for controlling AMF, we are hopeful that 

 the registrant (Bayer Corporation) will see fit to 

 officially register its use for this purpose. 



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



