Comparison of Baited and Unbailed 

 Traps for l\/lonitoring Plum Curculios 

 in Apple Orchards 



Ronald Prokopy, Bradley Chandler, Tracy Leskey, Starker Wright, 



and Jonathan Black 



Department of Entomology, University of Massachusetts 



In the Summer 1998 issue of Fruit Notes, we pre- 

 sented two articles describing results of 1998 tests in 

 which we evaluated responses of plum curculio (PC) 

 adults to several different types of unbaited traps in 

 commercial and unsprayed orchards. Here, we report 

 on 1999 tests in which we evaluated not only unbaited 

 but also baited versions of the same types of traps tested 

 in 1998 as well as a new trap type called a circle trap. 



Materials & Methods 



In eight commercial orchards, we evaluated three 

 types of traps: (a) black pyramid traps (24 inches wide 

 at base x 48 inches tall) placed on the ground next to 

 apple tree trunks, (b) black cylinder traps (3 inches 

 diameter x 12 inches tall) fixed vertically onto hori- 

 zontal branches within apple tree canopies, and (c) alu- 

 minum-screen "circle" traps (developed in Oklahoma 

 for pecan weevils) and wrapped tightly around ascend- 

 ing tree limbs, designed to intercept PC adults walk- 

 ing upward. Traps were placed in six blocks of apple 

 trees in each orchard. Each block consisted of seven 

 perimeter trees. Each tree (save one) contained one 

 unbaited and one baited trap of the above types. The 

 bait consisted of a combination of one polyethylene 

 vial containing limonene and two polyethylene vials 

 containing ethyl isovalerate (components of host fruit 

 odor found to be attractive to PCs in 1998 studies) plus 

 one rubber septum impregnated with grandisoic acid 

 (attractive male-produced pheromone of PC). Vials 

 were attached to the exterior of traps at mid height, 

 and the septum was placed inside the inverted wire- 

 screen funnel (boll weevil trap top) that capped each 

 trap and captured responding PCs. All traps were de- 

 ployed at bloom and were examined for captured PCs 

 every 3 to 4 days for 6 weeks thereafter. At each trap 

 examination, 15 fruit on each of the seven trees per 

 block were examined for PC oviposition scars. All 



blocks received two grower-applied sprays of 

 azinphosmethyl to control PC. 



In three small unsprayed orchards, we evaluated 

 unbaited and baited pyramid and cylinder traps as well 

 as clear Plexiglas squares (2 feet x 2 feet) fastened 

 vertically 5 feet above ground to wooden poles seated 

 in the ground. One side of each Plexiglas square was 

 coated with Tangletrap to capture alighting PCs. 

 Plexiglas traps were positioned with sticky-side fac- 

 ing woods either 6 feet from the edge of woods or 1 

 foot outside of perimeter foliage of apple trees. Traps 

 were placed in four blocks of apple trees in each or- 

 chard. Each block consisted of six perimeter trees. 

 Each tree contained one unbaited and one baited trap 

 (above type bait) of each trap type. Each block in two 

 of the orchards also received one unbaited and one 

 baited clear Plexiglas trap placed at the edge of woods. 

 All traps were emplaced at bloom. Every 3 to 4 days 

 thereafter for 6 weeks, traps were examined for cap- 

 tured PCs, and fruit were examined for PC scars. No 

 insecticide was applied to any of the blocks. 



Results 



In commercial orchards, significantly more (about 

 three-times more) total PCs were captured by pyramid 

 traps than by cylinder traps, with circle traps captur- 

 ing no PCs (Figure 1). There was no significant dif- 

 ference in captures between unbaited and baited traps 

 of any type (Figure 1). Disappointingly, none of the 

 three types of baited or unbaited traps yielded captures 

 whose amount or phenology (pattern of occurrence over 

 time) reflected even in a very minimal way the amount 

 or phenology of egglaying injury to fruit caused by 

 PC. If there were a perfect relationship between trap 

 captures and injury, then the statistical indicator of such 

 a relationship (called r) would have a value of 1.00. 

 Here, the r value describing the relationship between 



Fruit Notes, Volume 64 (Number 3), Summer, 1999 



