release from caps of varying sizes. By increasing the 

 cap height by 50%, our intent was to maintain steady 

 sugar release over a longer period. Unfortunately, 

 increasing cap height did not enhance either 

 concentration or duration of sugar release. By 

 increasing the cap diameter to 2 Vi', we were able to 

 substantially mcrease the amount of sugar put out by 

 each cap. However, by extending the outer edge of the 

 cap closer to the diameter of the sphere, we eliminated 

 the potential for even coverage by sugar-beanng runoff 

 It was apparent under visual observation of the 

 movement of stained sucrose that although we had 

 drastically increased the amount of sugar put out by 

 each cap, very little released sugar remained on the 

 sphere surface. Therefore, we abandoned any further 

 testing of fluted wax/sugar caps larger than 2-inch 

 diameter. 



Although the previous experiment did not yield an 

 improvement over our 2000 field-model sugar-release 

 caps, we found that all caps tested retained a substantial 

 amount of sucrose within the cap bodies long after they 

 had stopped releasing sugar to the sphere surfaces. 

 Unfortunately, with a fluted cap style (reliant on release 

 of sugar from the outside surfaces of the cap), the 

 remainder of solid sucrose is too deeply embedded in 

 the wax matrix to be readily available for dissolution 

 in rainfall. However, by direct observation of the 

 movement of rainfall onto and off of these caps, we 

 determined that a small amount of water moves slowly 

 through the wax matrix and is released to the sphere 

 surface at the bottom of the cap. For our third 

 experiment, we compared the rate of sugar release from 

 fluted caps versus release from new caps partitioned 

 at the top to allow retention of a small reservoir of 

 water. In assessments of sucrose found in runoff, fluted 

 caps were superior (Table 3), maintaining greater than 

 five grams of sugar release per inch of rainfall through 

 five accumulated inches, while reservoir-style caps 

 never exceeded three grams of sucrose release. 

 However, visual observations indicated that both 

 coverage and concentration of sucrose on spheres after 

 drying were far greater on spheres fitted with new 



reservoir-style caps. This observation was confirmed 

 by subsequent measurements of residual sucrose on 

 the sphere surface (Table 3). 



In our final experiment, we assessed the 

 effectiveness of five types of rodent guards, all formed 

 of hardware cloth. After only a day of exposure to 

 wild gray squirrels, any caps with any unprotected 

 surface were severely damaged. After one week, all 

 caps were consumed entirely, with the exception of 

 those fitted with an embedded top/bottom/side guard 

 combination. At the close of the two-week trial, all of 

 these fully protected caps remained intact, although 

 the integrity of the guard system showed signs of wear. 

 We are confident, though, that caps constructed with a 

 fully integrated wire guard can withstand the more 

 lenient assaults of standard orchard-dwelling rodents. 



Conclusion 



Given the variables of wax type, cap formulation 

 and size, shape, and density of cap, a vast array of sugar 

 release systems remain to be tested for use on pesticide- 

 treated wooden spheres. However, through trials to 

 date, we have arrived at an improved sugar delivery 

 system for testing under commercial orchard 

 conditions. Although these caps are still under study, 

 their performance has exceeded any other style tested 

 to date, and they hold the potential to markedly enhance 

 the effectiveness, practicality, and commercial viability 

 of wooden PTS. We will carry forward with field trials 

 of spheres equipped with the style of caps developed 

 here: 2-inch diameter, 15-20% paraffin, 50 grams total 

 mass, reservoir design, formed under 20 tons of 

 pressure, and fitted with an integrated rodent guard. 



A cknowledgem ents 



This project was supported by state and federal 

 IPM funds, along with grants from the Massachusetts 

 Society for Promoting Agriculture, the US EPA IR-4 

 Program, and the USDAPest Management Alternatives 

 Program. 



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Fruit Notes, Volume 66, 2001 



29 



