How Do Plum Curculios Approach 

 Host Trees and Pyramid Traps? 



Ronald Prokopy and Starker Wright 



Department of Entomology, University of Massachusetts 



The means by which plum curcuhos 

 approach host trees, whether by flight or by 

 crawhng, can provide important background 

 information leading toward optimization of 

 design and location of traps for monitoring and 

 possibly even controlling curculios. We report 

 here on several studies conducted during 1996 

 aimed at learning more about movement 

 patterns of curculios toward host trees and 

 pyramid traps under varying sorts of weather 

 conditions. 



Experiments & Results 



Movement Toward Host Trees. In our 



first experiment in a small unmanaged orchard 

 of 36 semi-dwarf trees owned by Hardigg 

 Industries of South Deerfield, MA, we wanted 

 to determine whether curculios entered the tree 

 by flying, by crawling, or by both means, and 

 whether mode of entry depended on weather 

 conditions. We coated the trunks of 12 trees 

 (every third tree) with a thick 1-inch-wide band 

 of Tangletrap about 2 feet above ground to 

 prevent curculios fi-om crawling up the trunk 

 and into the canopy. Direct observation of 

 curculios attempting to cross this sticky band 

 indicated that they were unsuccessful in doing 

 so. None of the tips of branches of these or any 

 other trees in the orchard reached closer than 2 

 feet above ground, thereby precluding curculios 

 from crawling onto branch trips to reach the 

 canopy. Height of grass was maintained below 

 4 inches. Another set of 12 trees (every third 

 tree) was not treated with Tangletrap to permit 

 curculio arrival both by crawling and by flight. 

 Every evening at 8 PM from May 19 (full bloom) 

 to June 7, we tapped the branches of each of 

 these 24 trees over white cloth sheets placed on 

 the ground beneath the canopy and collected all 



fallen curculios. We also obtained an hourly 

 record of temperature at a nearby location for 

 each day from May 19 to June 7. 



Results (Table 1, experiment 1) show that 

 that total number of curculios collected fi^om 

 trees having a band of Tangletrap was nearly 

 equal to that of trees without a band of 

 Tangletrap. Results (Table 1, experiment 1) 

 also show there was a significant positive 

 correlation between daily numbers tapped from 

 trees having a Tangletrap band, as well as from 

 trees without Tangletrap, and daily high 

 temperature. 



These results provide two valuable pieces of 

 information. First, a band of Tangletrap 

 around the tree trunk is of no apparent value in 

 preventing curculios from accessing host trees 

 and causing injury to fruit. One reason for this 

 lack of deterring effect may be that those 

 curculios which crawl up tree trunks and are 

 unable to pass beyond a sticky barrier 

 subsequently fly into the tree canopy, provided 

 the temperature is warm enough to permit 

 flight. We did, in fact, observe directly some 

 curculios behaving in this manner on warm 

 days. Second, our prediction at the outset that 

 numbers of curculios in tree canopies would be 

 equal on trees with and without a Tangletrap 

 band on warm days (signifying movement into 

 canopies largely or solely by flight) but would be 

 greater on trees without than with a 

 Tangletrap band on cool days (signifying 

 movement into canopies largely solely by 

 crawling) was not supported by the data. On 

 warm days, numbers were large on both types 

 of trees, indicating that curculios were prone to 

 fly into tree canopies on warm days. On cool 

 days, numbers were few on both types of trees, 

 indicating little tendency of curculios either to 

 fly or to crawl into trees on cool days. 



Fruit Notes, Volume 62 (Number 1), Fall, 1997 



