Areawide Patterns of Azinphosmethyl Resistance in Adult Male Platy nota idaeusalis (Lepidoptera: Tortricidae) in South central Pennsylvania

Abstract

Levels of resistance to azinphosmethyl in adult male populations of Platynota Idaeusalis (Walker) within apple, peach, pear, and cherry orchards and woodland from three regions in Adams County, Pa., were tested during 1986-1987. In Quaker Valley, significant differences among habitats were found only for brood I in 1986. However, LD50’s were generally highest for populations within apple and lowest for populations in peach and woods for both years. In 1987, a significant population-within-crop effect was found only for brood II. LD50’s of populations in three more northern orchards within Quaker Valley where azinphosmethyl + phosmet use was high were significantly higher than for two populations in southwestern apple orchards which received less of these pesticides. A comparison of three regions that varied in their mixture of crops and surrounding habitats in 1987 revealed no significant differences among regions. However, significant differences related to crops were found in brood II. LD50’s of populations in apple in Quaker Valley and Fox Hill were significantly higher than for populations in cherry or peach within each region. Low-density, susceptible adult male populations were trapped from wooded sites 1.3-5.0 km from the nearest apple orchards.