Table 2. Percentage of sugar/wax discs atop wooden PTS and 

 percentage of sugar/flour PTS having greater than 20% 

 estimated damage by feeding of rodents or other mammals, 

 based on visual inspection (bi-weekly) of 120 discs or spheres. 



Spheres damaged by 

 feedmg (%)* 



Weeks of field 

 exposure 



Discs atop 

 wooden PTS 



Sugar/flour 

 PTS 



2 

 4 

 6 



9 



10 

 10 



16 



28 

 37 



All sugar/wax discs and all sugar/flour spheres were replaced 

 at mid-season (after week 6) 



2 



4 





 



46 



47 



* Loss of 20% or more of mass (discs) or surface area 

 (sugar/flour PTS). 



o 



< 



LU 



a: 

 a. 

 < 



CD 



00 



00 0,5 1-0 15 20 2,5 30 35 40 45 

 CUMULATIVE RAINFALL (INCHES) 



Figure 1 . Visually estimated percent of original sugar remaining in sugar/wax 

 discs atop wooden PTS after exposure to rainfall in commercial apple orchards. 

 Visual estimates were based on color of discs, which range from red (no sugar 

 loss) to white (complete sugar loss). 



PTS (as assessed by color of discs) 

 declined in concert with the amount 

 of rainfall to which discs were 

 subjected during their 6-week 

 exposure period in commercial 

 orchards. The relationship between 

 amount of remaining sugar and 

 amount of rainfall appears to be 

 approximately linear and suggests that 

 very little sugar would remain after 6 

 inches of rainfall. Besides rainfall, 

 droplets of dew accumulatmg m 

 reservoirs of sugar/wax discs also 

 result in release of sugar onto the 

 surface of wooden PTS. This is 

 advantageous to sphere performance 

 durmg periods of dry weather. 



Residual Toxicity. After the first 

 6 weeks of field exposure under 4.17 

 inches (on average) of cumulative 

 rainfall, wooden PTS killed 37% of 

 alighting AMF compared with 69% 

 kill of alighting AMF by sugar/flour 

 PTS (Table 3). 



After 1 2 weeks of field exposure 

 of wooden PTS (accompanied by 

 replacement of sugar/wax discs at 6 

 weeks), 39% of 

 alighting AMF 

 died (Table 4). 

 Total rainfall 

 averaged 3.14 

 inches during 

 weeks 7-12 and 

 7.31 inches over 

 the entire 12 

 weeks of sphere 

 exposure. In 

 addition to 39% 

 mortality of 

 alighting AMF, 

 another 14% of 

 AMF, though 

 alive, were 



unable to fly 72 

 hours after 

 contact with 

 wooden PTS. 

 When a 20% 

 sugar solution 

 was applied to 

 1 2 - w e e k - 



5,0 55 60 6,5 



7,0 



32 



Fruit Notes, Volume 66, 2001 



