Improvement of Sugar-delivery 

 Systems for Rain-activated, 

 Pesticide-treated Spheres 



Starker Wright, Bradley Chandler, and Ronald Prokopy 

 Department of Entomology, University of Massachusetts 



Introduction 



Through use of odor-baited sticky red spheres, 

 effective behavioral control of apple maggot is possible 

 and has been widely reported in Fruit Notes. However, 

 the sticky material used to snare alighting apple maggot 

 flies (AMF) is very difficult to handle and requires 

 frequent maintenance. In order to develop trap-based 

 AMF control that is practical for commercial adoption, 

 we have worked for many years toward development 

 of pesticide-treated spheres (PTS) to substitute for 

 inefficient sticky-coated spheres. Although PTS have 

 shown great promise in both laboratory and field trials, 

 the major challenge we face is continuously supplying 

 the sphere surface with enough sugar to stimulate fly 

 feeding, thereby allowing PTS to achieve maximum 

 toxicity to AMF with a minimal dose of insecticide. 

 To date, we have developed two approaches to 

 providing a consistent supply of sucrose to sphere 

 surfaces under field conditions: a reusable wooden PTS 

 with an external source of feeding stimulant and a 

 disposable sugar/flour PTS whose entire body consists 

 of sugar and starches (see Fruit Notes, Volume 65). 



Data from field and laboratory trials in 2000 

 strongly suggest that wooden PTS retain toxicity to 

 AMF for at least 12 weeks, while sugar/flour PTS may 

 begin to lose their toxic effects after as little as six 

 weeks of field exposure. From direct observations of 

 fly feeding on PTS and assessments of fly behavior 

 after exposure, it appears that, along with some sugar, 

 some toxicant is lost from the sugar/flour PTS during 

 rainfall. Given this, we believe that further 

 development of re-usable wooden PTS may hold 

 greater long-term promise for commercially viable 

 behavioral control of AMF than do sugar/flour PTS. 



Since 1997, we have worked toward development 

 of a wooden PTS system focusing on use of a sucrose- 



bearing top-cap affixed to each sphere which, under 

 rainfall, releases a small amount of sucrose onto the 

 sphere surface. Thus, as surface sugar is dissipated 

 under rainfall or heavy dew, it is replaced with sucrose 

 from a source atop the PTS. In 1997 and 1998, we 

 attempted to form these caps of nearly pure sucrose, 

 finding quickly that the pure sugar caps were highly 

 prone to breakdown under conditions of high humidity. 

 In 1999, we formed and tested flat-topped, 1 Vi" caps 

 consisting of 85% sucrose bound in 15% paraffin (25 

 grams total mass). Although these caps worked for a 

 short time in the field (~3 weeks), they ran out of sugar 

 well before the close of the season. 



In 2000, we again tested caps consisting of 85% 

 sucrose bound in 15% paraffin, but modified the caps 

 in 3 major ways: I) we increased the diameter to 2 

 inches; 2) we doubled the mass to 50 grams; and 3) we 

 formed the caps using a hydraulic press that stamped 

 eight flutes into the top of each cap, ensuring even 

 distribution of sucrose-bearing runoff Upon lab 

 testing, this style of cap was effective through five 

 inches of accumulated rainfall (roughly equal to five 

 weeks of field exposure). This was by far the best- 

 performing wooden PTS to date, but we needed to 

 address two major shortcomings: 1) further 

 modification of caps to ensure effectiveness through 

 at least mid-season (six to eight inches of rainfall), and 

 2) prevention of rodent damage to caps. From the 

 laboratory-based studies reported here, our goal was 

 to improve the consistency and durability of sugar 

 release from wax/sugar caps for deployment on wooden 

 PTS in 2001. 



Materials & Methods 



For each of the trials described below, we mounted 

 experimental caps on 3. 3 -in wooden spheres prior to 



Fruit Notes, Volume 66, 2001 



25 



