Table 2. Of plum curculios that left vials in which they were contained (i.e. 

 curculios that were active), proportions that arrived on vertical apple twigs 

 (1/2 inch diameter) or on cylindrical vertical mimics (1 or 3 inches diameter) 

 of either apple twigs (black) or apple foliage and fruit (yellow). 



* Numbers followed by a different letter are significantly different at odds of 

 19:1. 



mimic foliage and fruit borne by twigs and were 

 similar in appearance to yellow-green plastic 

 traps used commercially to capture cotton boll 

 weevils. The black cylinders were intended to 

 mimic twigs themselves. Each cylinder was po- 

 sitioned vertically on a branch over an upright 

 clipped twig, used as support. For each trial, 

 we collected curculios (by branch tapping) from 

 nearby trees, placed ten in a vial, and attached 

 the vial in horizontal position to a branch about 

 9 inches from a cylinder. The curculios could 

 crawl or fly directly from the vial opening to- 

 ward the cylinder. Of the curculios that left 

 vials, we recorded proportions that arrived on 

 a cylinder during a 30-minute trial period. 



Results 



There were no significant differences in 

 numbers of curculios captured per trap among 

 sticky-coated Plexiglas traps in low position, 

 sticky-coated Plexiglas traps in high position, 

 and black pyramid traps (Table 1). These re- 

 sults confirm and are remarkably similar to 

 those of the 1996 study reported in the 1997 

 Winter issue of Fruit Notes. Importantly, we 

 found here that increases in captures by sticky 

 Plexiglas traps but not by black pyramid traps 

 were significantly positively correlated with 

 increases in fruit damage caused by plum 

 curculios the following day. Also, captures by 



sticky Plexiglas traps as well as fruit damage 

 were significantly positively correlated with 

 temperature, with the former also significantly 

 negatively correlated with wind speed. 



Among plum curculios that left vials in 

 which they were released on apple tree 

 branches, 22-24% arrived on upright test twigs 

 or on 1 -inch-diameter or 3-inch-diameter up- 

 right yellow cylinders (Table 2). Significantly 

 greater proportions (41-48%) arrived on upright 

 black cylinders (Table 2). All observed curculios 

 arrived on twigs and cylinders by crawling. 

 None arrived by flight. 



Conclusions 



The findings reported here, though still pre- 

 liminary, encourage us to believe that improved 

 variants of the sticky Plexiglas squares and tall 

 black cylinders studied here could be more suit- 

 able than black pyramids for monitoring 

 curculios, because captures by these traps bet- 

 ter coincide with periods of curculio damage to 

 fruit than captures by black pyramid traps. 

 Sticky Plexiglas squares placed adjacent to tree 

 canopies are much too cumbersome for wide- 

 spread use by growers, but a simplified non- 

 sticky version (possibly incorporating attractive 

 canopy-mimicking stimuli) might be an effec- 

 tive substitute. Similarly, an improved version 

 of a black twig-mimicking trap could be of con- 



Fruit Notes, Volume 63 (Number 1), Winter, 1998 



15 



