Mines o£ 1st generation larvae can be first detected in late 

 pink or bloom, those of 2nd generation larvae in late June or early 

 July, and those of 3rd generation larvae in mid or late August. 

 Generations may overlap owing to the extended period of egg-laying. 



Injury . STLM do not directly injure apple fruits. Rather the dam- 

 age results from injury to the leaves caused by larval feeding. 

 There is some suggestion, not yet confirmed that STLM larval feeding 

 interferes with the ability of leaves to produce or transfer to fruit 

 a hormone which inhibits ethylene production by the fruit. STLM 

 injury may result in greater than normal concentration of ethylene 

 within the atmosphere of the tree canopy. 



Principal effects of extensive STLM larval feeding on Mcintosh 

 and other earlier-season cultivars such as Milton, Early Mcintosh, 

 Wealthy, and Puritan may be early ripening of fruit, premature fruit 

 drop, reduction in fruit size and color, reduction in fruit firmness 

 and storagability , and/or reduction in fruit set the following year. 



Additional effects of STLM feeding may be: (a) greater sus- 

 ceptibility of larval-infested leaves to phytotoxic effects of insecti- 

 cides, fungicides, or calcium chloride nutrient sprays; (b) reduced 

 capability of larval-infested leaves to absorb growth-regulator 

 sprays applied to prevent early fruit drop or promote ripening, or 

 (c) compounding of detrimental effects of large spider mite popula- 

 lations, low plant nitrogen, or poor pruning. 



In New York, there have been little or no detrimental effects 

 of large STLM populations on Red Delicious. 



Natural Enemies . Several species of tiny wasps have been found 

 parasitizing STLM larvae in New York and Southern New England. The 

 parasite larvae hatch out from eggs deposited in STLM mines and suck 

 out the body fluids of STLM larvae. In Massachusetts, we have found 

 at least 5 such parasite species, the most abundant of which is 

 Apanteles ornigis . Among 9 Massachusetts commercial apple orchards 



We speculate that there might be a more or less continual immig- 

 gration of parasite adults from unsprayed trees into commercial or- 

 chards during the growing season. However, regular application of 

 insecticide from petal fall through early August undoubtedly kills 

 most adults immigrating at this time. This is borne out by the fact 

 that both Weires and we find very little parasitism of 1st and 2nd 

 generation STLM larvae. Adoption of integrated pest management tech- 

 niques and corresponding reduction of unneeded insecticide applications, 

 especially in July, could open the way to increased levels of para- 

 sitism of 2nd generation larvae. Termination of insecticide appli- 

 cations by early August may allow comparatively high survival of 

 parasites attacking 3rd generation larvae. Such parasitism of these 

 larvae, together with natural enemies feeding upon overwintering 

 STLM pupae, could result in substantial mortality to overwintering 

 numbers of STLM. 



