SCRAPING AND BANDING FOR CODLING MOTH CONTROL 7 



EFFECT OF DENSITY OF INFESTATION ON NUMBER OF 

 LARVAE CAUGHT IN LIMB BANDS AND TRUNK BANDS 



Where the infestation was low, averaging only 10 larvae per tree, 

 66 percent more larvae were caught in limb bands than in trunk bands, 

 and 106 percent more were caught in both types of bands than in bands 

 on trunks only. On the other hand, where the infestation was high, 

 averaging 265 larvae per tree, only 25 percent more were in limb 

 bands than in trunk bands, and 47 percent more in both types of bands 

 than in trunk bands alone. This difference may be explained by the 

 fact that in more severe infestations a greater proportion of wormy 

 apples fall to the ground, and a larger proportion of the larvae from 

 these fallen fruits get into the trunk bands than into the bands on the 

 scaffold limbs farther up. 



INFLUENCE OF APPLE VARIETY ON NUMBER OF 

 LARVAE CAUGHT 



Varieties of apple differ in their adaptability to scraping and band- 

 ing. Jonathan and Rome Beauty are particularly well suited for 

 maximum scraping and banding efficiency, whereas Delicious and 

 Winesap are much less so, because of their knotty limb surfaces, cracks, 

 crotches, and numerous scallops on the trunks (figs. 1, 2, and 3). 



These differences are reflected in the varying numbers of larvae 

 caught on trees of the four varieties tested (table 2). The total 

 captures are also influenced by the susceptibility of the different varie- 

 ties to codling moth attack, a factor not directly involved in the work 

 reported on in this circular. 



The more difficult a tree is to scrape and band the less efficient the 

 bands are in capturing the larvae. The more severely infested varie- 

 ties, such as Jonathan, should be given special attention in the treat- 

 ment, not only to protect their own crop but also that of less suscept- 

 ible neighboring varieties. 



TIME REQUIRED FOR BETA-NAPHTHOL BANDS 



TO KILL 



In tests of freshly applied bands on tree trunks in the orchard, all 

 the larvae that had been in the bands from 24 hours to 8 days were 

 killed by the chemical, whether the bands were removed from the 

 trees and kept in the orchard at temperatures of 60° to 98° F. or were 

 taken to a semiclark, cool basement at 66° to 68°. Tests in which 

 orchard conditions were simulated showed that all the larvae in bands 

 on the sunny side of a section of apple limb 4 inches in diameter were 

 killed within 8 hours. An exposure of several hours in the sunshine 

 and overnight killed all the larvae in 18 hours. On the shady side 

 of the same sticks all larvae were killed in 24 hours. With lower tem- 

 peratures, as in the basement at 66°, only 90 percent were killed in 

 24 hours. In properly prepared bands the chemical kills the larvae 

 so quickly that few are able to transform to pupae. . 



