100 



a: 



6WKS 



2.0% 0.5% 1.0% 2.0% 4.0% UNT 



IM 



SPINOSAD 



9 WKS 



O 



100 



50 



2.0% 0.5% 1.0% 2.0% 4.0% UNT 



IM SPINOSAD 



1 12 WKS 



LiiiL 



2.0% 0.5% 1.0% 2.0% 4.0% UNT 



IM 



SPINOSAD 



Figure 3. Percent mortality of flies 72 hours after exposure 

 for 10 minutes in laboratory cages to PTS retrieved 6, 9, or 

 1 2 weeks after deployment in an unsprayed orchard in early 

 July. Each value is based on sphere exposure to 20 flies (10 

 per sphere x 2 spheres per treatment). Treatments were: 2% 

 imidacloprid (IM) in paint on sphere; 0.5, 1.0, 2.0, or 4.0% 

 spinosad in discs atop spheres; or untreated spheres (UNT). 



water at an intensity and droplet size 

 approximating medium rainfall. Discs atop 

 spheres contained either, 0, 0.001, 0.01, 0.1, or 

 1 .0% spinosad. After each inch of artificial rain, 

 a sphere was allowed to dry for 24 hours before 

 the next inch was applied. Spheres were 

 assessed for fly killing power using above 

 procedures, accompanied by careful observation 

 of fly feeding behavior during each 10-minute 

 trial. A fly was considered to have fed if it 

 remained still with proboscis fully extended for 

 at least 10 seconds. 



Results 



Results of Experiment 1 (Figure 1) for 

 commercial orchard plots show that, on average, 

 the fewest AMF captured on interior monitoring 

 traps and the fewest injured fruit in samples taken 

 at harvest were in plots surrounded by 2003- 

 version PTS topped by discs containing 4.0% 

 spinosad. By each of these measures, 2003- 

 version PTS outperformed both 2002-version 

 PTS (whose surface was treated with 

 imidacloprid) and insecticide spray for AMF 

 control. When assayed in the laboratory (after 

 retrieval from orchard plots) to AMF placed 

 directly on the PTS, again 2003-version PTS 

 containing 4.0% spinosad in the disc 

 outperformed 2002-version PTS whose surface 

 was treated with imidacloprid (Figure 2). 

 Especially impressive was the finding (Figure 

 2) that 74%) of adults died after placement on 

 2003-version PTS exposed for 12 weeks in 

 commercial- orchard trees. During these 12 

 weeks, 18-22 inches of rain fell on the PTS. 



Results of Experiment 2 (Figure 3) show that 

 after 6 weeks of exposure in unsprayed orchard 

 trees, 2003-version PTS topped by discs 

 containing 0.5, 1 .0, 2.0, or 4.0% spinosad were 

 about equally effective in killing adults placed 

 directly on the spheres (50-65% mortality). 

 Results were nearly the same after 9 weeks of 

 field exposure (40-55%) mortality). After 12 

 weeks of field exposure, however, there was a 

 consistent trend toward greater toxicity (from 

 38 to 83%) with increasing dose (from 0.5% to 

 4.0%) of spinosad in the disc. Imidacloprid- 

 treated, 2002-version PTS were inferior to all 



Fruit Notes, Volume 69, Spring, 2004 



23 



