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PERCENTAGE PARASITISM 



Figure 1. Treatment thresholds for apple blotch leafminer. 



tion leafminer adults if needed, because diflurbenzuron is References 

 not disruptive to biological mite control. 



Converting Front Pesticide Management to 

 Biological Control of Apple Leafminers 



Conversion from pesticide management of apple 

 leafminers to management based largely on conservation 

 of parasites is essential if growers are to reduce pest 

 management costs and the threat of ever increasing pesti- 

 cide resistance in leafminer populations. This goal can be 

 reached only as part of an integrated reduction in orchard 

 pesticide use to increase, to the greatest extent possible, 

 the insecticide-free period from mid- to late season. 

 Recognition of the principal parasite species and the 

 ability to tell a leaf mine that produced a parasite from one 

 that produced a moth are essential. Sharp tweezers and a 

 hand lens are the required tools for this determination. 

 Training can be obtained from regional fruit extension 

 agents. Regular assessment of proportions of mines para- 

 sitized can help growers remain aware of the status of 

 leafminer populations in their orchards and can be used to 

 modify recommended chemical control thresholds. 



Barrett, B A. and CD. Jorgensen. 1986. Parasitoidsofthe 

 western tentiform leafminer, Phyllonorycter elmaella 

 (Lepidoptera: Gracillariidae) in Utah apple orchards. 

 Environ. Entomol. 15:635-641. 



Dutcher, J.D. and JA. Howitt. 1978. Bionomics and 

 control oi Lithocolletis blancardella in Michigan. /. Econ. 

 Entomol. 71:736-738. 



Laing, J.E. and J.M. Heraty. 1981. Establishment in 

 Canada of the parasite Apanteles pedias Nixon on the 

 spotted tentiform leafminer, Phyllonorycter blancardella 

 (Fabr.). Environ. Entomol. 10:933-935. 



Laing, J.E. and J.M. Heraty. 1987. Overwintering of 

 Phyllonorycter blancardella (Lepidoptera: Gracillariidae) 

 and its parasites, Pholetesor omigis and Pholetesor pedias 

 (Hymenoptera: Braconidae), in southwestern Ontario. 

 Environ. Entomol. 16:1157-1162. 



Maier, C.T. 1984. Abundance and phenology of parasi- 

 toids of the spotted tentiforn leafminer, Phyllonorycter 



