Table 2. Response index (RI) of plum curculio adults 

 to six liost fruit odor compounds evaluated in 

 Massachusetts in 2000 at tliree different release rates. 

 For each compoimd, only that release rate wiiich 

 yielded tlie higliest RI value 

 of all is given. 



*RI value of 32 or greater can be considered as 

 significantly diflFerent from zero at odds of 9: 1 . 



release rate or was unbaited. Vials were placed inside the 

 cylinder component of the screen funnel top of the trap. Over 

 a 7-\veek period from early May to late June, 264 traps were 

 deployed in Massachusetts and another 264 in Ohio for re- 

 evaluation of 17 compounds tested in 1999 plus five other 

 compounds that were comparatively inexpensive to purchase 

 from a commercial supplier (Table 1). In addition, six com- 

 pounds that were much too expensive to evaluate in both 

 states were evaluated only in Massachusetts (Table 2). Traps 

 were examined for captured PCs every 2-3 days and rotated 

 in position after each examination. 



To measure attractiveness of a particular release rate 

 of a particular compound, a Response Index (RI) was cre- 

 ated by subtracting the total number of PCs responding to 

 an unbaited control trap (C) from the total number respond- 

 ing to its corresponding baited trap (BT), dividing by the 

 total number of PCs captured by the C and BT traps and 

 multiplying by 100. Thus, RI = [(BT-C)/BT+C)] x 100. The 

 greater the RI, the more attractive the compound was at that 

 release rate. RI values of 32, 50 and 60 correspond to PC 

 captures by baited traps as being t\vo, three and four times 

 greater, respectively, than captures by control traps. 



hexenyl acetate (50), benzaldehyde (45), 3-penten- 

 2-ol (45), ethyl isovalerate (38), geranyl propionate 

 (33), isopropyl acetate (33), nonenal (33) and 2- 

 propanol (33). 



Also given in Table 1 are highest RI values 

 from 1999 tests involving 17 of the 22 compounds. 

 Together, data from 1999 and 2000 tests show that 

 seven of the 1 7 compounds tested in both years 

 had RI values each year of 32 or greater at the most 

 attractive release rate. In descending order of at- 

 tractiveness (where RI values were averaged across 

 both years even though corresponding release rates 

 may have been different), these seven compounds 

 were; 1-pentanol (65), hexyl acetate (59), 

 phenylacetaldehyde (48), benzaldehyde (46), 

 geranyl propionate(46), ethyl isovalerate (39), and 

 2- propanol (33). In addition, the average RI value 

 for R(+) limonene in 1999 and S(-) limonene 

 (which contains 25% R(+) limonene) in 2000 was 

 65. 



Results for the six expensive compounds 

 evaluated only in Massachusetts (Table 2) show 

 that only two had RI values of 32 or greater at the 

 most attractive release rate: ocimene (56) and 

 cubebene (33). Ocimene is a biochemical byproduct of li- 

 monene. 



Conclusions 



Results from 2000 tests in conjunction with those from 

 1999 tests suggest that 10 compounds are especially worthy 

 of further consideration as affordable odor attractants for 

 PC. In alphabetical order these are: benzaldehyde, ethyl 

 isovalerate, geranyl propionate, hexyl acetate, Z-3-hexenyl 

 acetate, limonene, 1-pentanoI, phenylacetaldehyde, 3- 

 penten-2-ol, and 2-propanol. 



As reported elsewhere in this issue of Fruit Notes, ben- 

 zaldehyde and ethyl isovalerate proved attractive to PCs 

 when each was in combination with synthetic pheromone in 

 traps intended to capture PCs immigrating into orchards as 

 well as in traps intended to capture PCs beneath or within 

 apple tree canopies. Limonene in combination with phero- 

 mone also showed evidence of attractiveness to PCs under 

 the latter condition. Each of the 10 most promising host 

 odor compounds reported here merits evaluation in combi- 

 nation with pheromone for attractiveness to PC. 



Results 



A cknowledgements 



Of the 22 compounds evaluated in both Massachusetts 

 and Ohio (Table 1), 12 had a RI value of 32 or greater (= 

 minimum RI value suggestive of significant attractiveness) 

 at the most attractive release rate. In descending order of 

 attractiveness, these were 1-pentanol (71), S (-) limonene 

 (65), phenylacetaldehyde (64), hexyl acetate (50), Z-3- 



This study was supported by awards from the New 

 England Tree Fruit Growers Research Committee, Massa- 

 chusetts Horticultural Research Center Trust Funds, the 

 USDA Northeast Regional Integrated Pest Management 

 Competitive grants program, and state of Massachusetts In- 

 tegrated Pest Management Funds. 



it it ^ it it 



Fruit Notes, Volume 65, 2000 



31 



