- 3 



appeared slightly depressed and retained a green color even when the 

 remainder of peach skin background color had become reddish. in a few 

 instances a rather large droplet of clear gummy ooze exuded from the punc- 

 ture as well, which we took to indicate an active larva burrowing within the 

 fruit. Over time, a small, circular black spot developed where the female 

 fly had punctured the fruit. Injured fruit were seen with multiple punc- 

 tures in some cases, while others were only punctured once. Spots were 

 similar to small lesions of Peach Scab and positive identification required 

 removing the skin to look for eggs and/or burrows beneath. 



A cluster of numerous eggs could be seen easily with a 10X hand lens 

 and already-hatched eggs appeared shriveled. We were unable to retrieve any 

 larvae, although extensive brownish burrows were evident. Such trails dif- 

 ferred from those of AMF, with the majority confined to an area beneath the 

 puncture within 1 cm (0.^ in.) of the surface and rarely larger than 2 cm 

 (0.8 in.) in diameter. Between 75^ and 100^ of fruit were infested, 

 necessitating substantial culling of the most severely attacked fruit and 

 marketing the rest as "orchard run" at a reduced price. 



No larvae were successfully reared to pupation due to rapid rotting of 

 infested fruit when held at room temperature, although WHF are reportedly 

 able to reach pupation on this host (2). 



MONITORING AND CONTROL 



Presently, we do not know what monitoring techniques work best for WHF 

 nor whether monitoring is even necessary in most years. We anticipate, 

 however, that yellow sticky boards or green sticky spheres (k) may be effec- 

 tive monitoring devices. We hope to look into this question in 1986. 



Prior to our visit to the Granville orchard, the grower had applied a 

 single carbaryl treatment, and a careful check of remaining fruit and trees 

 revealed no adult flies. Other registered insecticides applied against 

 usual peach pests likely also will control WHF, although overlap of fly 

 activity with peach harvest would clearly limit choices to materials with 

 short pre-harvest interval requirements. 



CONCLUSION 



It is our belief that the walnut husk fly injury we observed was simi- 

 lar to the 1968 New York report mentioned earlier, when the crop of native 

 nuts was also found to be very small. We have no reason to believe that 

 resistance to insecticides played a role in our I985 infestation, so we 

 conclude that the absence of native hosts caused mated females to emigrate 

 to adjacent peach blocks in search of oviposition sites. Due to the like- 

 lihood of poor WHF larval survival in rapidly rotting peach flesh, and from 

 what is known of Tephritid host selection behavior, it would seem very un- 

 likely that WHF would switch preferred hosts and become a "new" pest of 

 peach. Nonetheless, in years when native hosts produce few nuts, or should 

 clearcut logging remove native hosts adjacent to peach blocks, growers 

 should, at the very least, be aware of the possibility of fruit injury and 

 monitor flies using either visual traps or direct observation of adult acti- 

 vity. 



