Table 2. Control of apple maggot flies by odor-baited wooden pesticide treated 

 spheres (PTS), sugar/flour PTS, sticky spheres or three applications of 

 azinphosmethyl in blocks of apple trees in commercial orchards. 



Mean % maggot-injured apples'* 



Wooden 

 PTS 



Sugar/flour 

 PTS 



Sticky 

 Spheres 



Azinphosmethyl 



0.56b 



0.32ab 



0.32ab 



0.11a 



* Total of 2800 fruit per treatment (100 fruit per block on each of four sampling 

 dates-2 weeks apart-from late July until harvest). Numbers followed by a different 

 letter are significantly different at odds of 19:1. 



Results 



Laboratory bioassays revealed (Table 1) that 

 after 12 weeks of exposure to outdoor sunlight 

 and 11 inches of natural rainfall, wooden 

 spheres treated with 1.5% a.i. imidacloprid WP 

 in Glidden paint killed 90% of arriving flies. 

 Such treatment also rendered all flies incapable 

 of lajdng eggs after feeding and required that a 

 fly feed on the sphere surface for a median time 

 of only 60 seconds to ingest enough toxicant to 

 die. Performance of wooden spheres treated 

 with 1.5% imidacloprid EC was slightly but not 

 significantly inferior, killing 87% of arriving 

 flies. At lower concentrations (0.5% a.i.), nei- 

 ther the WP nor EC formulation performed as 

 well (75% and 45% kill, respectively) as the 1.5% 

 a.i. WP formulation. 



In our second experiment (Table 2), sugar/ 

 flour PTS coated with 1.5% imidacloprid WP in 

 Glidden paint performed as well as sticky 

 spheres in providing direct control of apple 

 maggot. Wooden PTS coated with 1.5% 

 imidacloprid in Glidden paint and fitted with a 

 3-cm-diameter sucrose ring were inferior Two- 

 to-three insecticide sprays resulted in the least 

 damage. 



Conclusions 



Our first experiment provided us with the 

 formulation of a low dose of a safe and highly 

 effective insecticide (1.5% a.i. imidacloprid WP) 

 that can be combined with a particular type of 

 paint (Glidden Red Latex Gloss Enamel) which 

 offers very long and effective residual activity 

 of imidacloprid under field conditions. 



Although all sphere types used in the sec- 

 ond experiment performed quite well in the face 

 of high fly pressure, shortcomings need to be 

 addressed and improvements need to be made 

 before future use of PTS for controlling apple 

 maggot in commercial orchard IPM blocks. 

 Regarding wooden PTS, the caramelized sucrose 

 rings melted away before the end of the field 

 season, contributing to the reduced effective- 

 ness of these spheres. Some of the sugar/flour 

 PTS were eaten by birds and rodents while oth- 

 ers were overgrown by fungi on the sphere sur- 

 face, thus reducing the number of effective 

 spheres comprising the barrier to fly entry into 

 some blocks. 



For 1998 deployment of wooden PTS, we 

 plan to reformulate the sucrose ring atop the 

 sphere to improve residual effectiveness of the 



Fruit Notes, Volume 62 (Number 4), Fall, 1997 



