Evaluation of Baited and Unbaited 

 Traps for IVIonitoring Plum Curculios 

 in Commercial Apple Orchards 



Ronald Prokopy, Bradley Chandler, Starker Wright and Jaime Pinero 

 Department of Entomology, University of Massachusetts 



In the summer 1999 issue oi Fruit Notes we reported in 

 1999 tests in which we compared odor-baited with unbaited 

 traps for monitoring plum curculios (PCs) in commercial 

 and unsprayed orchards. The odor used was a combination 

 of two synthetic components of host fruit odor (ethyl 

 isovalerate and limonene) plus synthetic male-produced sex 

 pheromone (grandisoic acid). Odor-baited and unbaited traps 

 were of three types: pyramid, cylinder and Circle. Unfortu- 

 nately, none of these trap types captured significantly more 

 PCs when baited than when unbaited. 



Here, we evaluated each of six synthetic components of 

 host fruit odor in combination with grandisoic acid and in 

 association with pyramid, cylinder and Circle traps in 12 

 commercial apple orchards in 2000. The orchards were those 

 selected for a study of the influence of orchard and border 

 area architecture on third-level IPM practices. 



Materials & Methods 



The three types of traps were: (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 horizontal 

 branches within apple tree canopies, and (c) aluminum- 

 screen "Circle" traps (developed by a grower named Edmund 

 Circle in Oklahoma for pecan weevils) wrapped tightly 

 around ascending tree limbs and designed to intercept PC 

 adults walking upward. 



The six synthetic components of host fruit odor were 

 among the most attractive of the 30 components evaluated 

 in 1999 in conjunction with boll weevil traps placed on the 

 ground (results reported in the summer 1999 issue of Friiii 

 Notes). They were benzaldehyde, decanal, ethyl isovolerate, 

 hexyl acetate, limonene, and trans-2-hexenal. Each was 

 purchased from Aldrich Chemical Company and was de- 

 ployed in small polyethylene vials that fit into the screen- 

 funnel top of a boll weevil trap that capped each pyramid, 

 cylinder or Circle trap. The release rate of each compound 

 was about 10 milligrams per day (achieved by adjusting the 

 number of vials per trap according to compound volatility). 



Each baited trap also contained a plastic dispenser of 

 grandisoic acid (obtained from Chem-Tica, Inc. in Costa 

 Rica) designed to release about 5 milligrams of pheromone 

 per day. 



Traps were placed in plots of four apple trees in each of 

 the 1 2 orchards. Each plot consisted of seven perimeter trees. 

 Each tree (save one) contained one baited or one unbaited 

 trap of the above three types. All three baited traps in a 

 given plot received the same odor. In each orchard, each of 

 three plots received a synthetic fruit volatile in combination 

 with grandisoic acid. The fourth plot received grandisoic 

 acid alone. In all, there were six replicates of each synthetic 

 fruit volatile among the 12 orchards. 



All traps were deployed at tight cluster or early pink 

 (April 28-May 4). Traps were examined for captured PC 

 beginning at petal fall (May 9) and every 3 to 4 days there- 

 after for 7 weeks until June 27. Vials of benzaldehyde and 

 dispensers of grandisoic acid were renewed on May 28-30 

 (mid-way during the experiment). At each trap examina- 

 tion, 20 fruit on each of the six trapped trees per plot were 

 examined for PC oviposition scars. All plots received two 

 or three sprays of azinphosmethyl or phosmet to control PC. 



Results 



For PC captures summed across all tliree trap types (bot- 

 tom of Fig. 1 ), results show that traps baited with grandisoic 

 acid alone captured no more PCs than unbaited traps. Among 

 the six synthetic fruit volatiles tested in combination with 

 grandisoic acid, three captured about twice as many total 

 PCs as did coiTesponding unbaited traps: benzaldehyde, ethyl 

 isovalerate and limonene. For each of these three com- 

 pounds, captures by baited pyramid traps were never more 

 than twice as great as captures by unbaited coiTesponding 

 pyramid traps, whereas captures by baited cylinder or Circle 

 traps were always more than twice as great as captures by 

 corresponding unbaited cylinder or Circle traps (Fig. 1). 

 Owing to the limited number of replicates (six per treatment) 

 and variability among replicates, there were no significant 

 differences in PC response to baited versus unbaited traps, 



32 



Fruit Notes, Volume 65, 2000 



