Table 1. Captures of feral AMF on unbailed monitoring traps and 

 percent injury to fruit by AMF in 28 plots of apple trees in seven 

 commercial orchards. 



Treatment 



No. AMF 

 captured per plot* 



Fniit injury per 

 plot (%) 



Wooden PTS 

 Sugar/flour PTS 

 Sticky Spheres 

 Insecticide Sprays 



21.8 

 25.8 

 33.2 

 21.7 



003 

 016 

 006 

 Oil 



* Four unbailed spheres per plot 



was tested twice: immediately upon return 

 from the field (with no supplemental feed- 

 ing stimulant), and again after application of 

 a 20% sucrose solution to stimulate fly feed- 

 ing. Fly residence time on spheres and fly 

 condition (alive or dead) 72 hours post-ex- 

 posure were recorded for each fly. In all, we 

 tested 2240 AMF (individually) on a total of 

 224 PTS. 



Results 



vidual PTS of each type from each orchard and returned them 

 to the laboratory for testmg. We directly assessed the re- 

 sidual fly-killmg power of each PTS type by exposing 20 

 AMF to each sphere type from each orchard. Each sphere 



Table 2. Percentage of PTS receivmg greater 

 than 20% damage by rodent feeding, based on 

 visual inspection (bi-weekly) of 180 spheres 

 of each type. 



Spheres damaged by rodent 

 feeding (%)* 



All sugar/wax caps and sugar/Jlour spheres 

 replaced at mid-season. 



1 

 4 

 6 



* Loss of 20% or more surface area 

 (sugar/flour PTS) or mass (sugar/wax caps). 



Treatment Effectiveness. Comparisons 

 of AMF captures on unbailed monitoring 

 spheres on interior trees of each plot (Table 

 1 ) show that the number of AMF that pen- 

 etrated into plots surrounded by wooden PTS 

 was no greater than the number that pen- 

 etrated into plots that received two to three 

 insecticide sprays. Although differences were slight, wooden 

 PTS actually numerically outperformed both sugar/flour PTS 

 and sticky spheres. Fruit damage levels between plots were 

 very difficult to compare and were not particularly reliable 

 for this trial, given the near total lack of AMF damage in any 

 plot. Even so, wooden PTS performed as well as or better 

 than any other treatment. 



Structural Integrity. In order for spheres to maintain 

 effectiveness throughout a field season, they must be some- 

 what resistant to naturally damaging in-orchard influences, 

 particularly rodents and mold. Results from this trial clearly 

 indicated that no advantage in combating these influences 

 was gained by altering sphere color from red to black. There- 

 fore, all results focus only on structural integrity of wooden 

 PTS versus sugar/flour PTS (pooled data from red and black 

 spheres). 



Through the years of development of PTS, feeding by 

 rodents on spheres has been a significant obstacle to large- 

 scale implementation. After only 4 weeks of field exposure 

 (Table 2), 14,7% of caps atop wooden PTS had lost 20% or 

 more of their mass to rodent feeding. Similarly, after the 

 same period, 14% of sugar/flour spheres had lost 20% or 

 more of their surface area to rodent consumption. Destruc- 

 tion of both sugar/wax caps (wooden PTS) and sugar/flour 

 PTS by rodents increased in intensity as the season pro- 

 gressed, reaching 20.5% and 35.4% rodent damage, respec- 

 tively, after 6 weeks of field exposure. After 6 weeks of ex- 

 posure, all sugar/flour spheres and all caps atop wooden 

 spheres were replaced. Unfortunately, the trend of rodent 

 feeding established in the first half of the season confinued 

 until trap removal after 6 additional weeks of exposure. 

 During this interval, 3 1 .4% of caps on wooden PTS lost 20% 

 or more of their mass to rodents, faring only slightly better 

 than sugar/flour PTS (43.7%) losing 20% or more surface 

 area). 



Fruit Notes, Volume 65, 2000 



47 



