Seasonal Occurrence and Density of Phyllonorycter spp. (Lepidoptera: Gracillariidae) and Major Parasitoids in Missouri Apple Orchards

Abstract

Seasonal occurrence and density of Phyllonorycter spp. and their major parasitoids were examined in central and west-central Missouri apple orchards for 2 yr. All sites were commercial orchards under standard spray programs. Two of the study orchards were infested with Phyllonorycter blancardella (F.), the spotted tentiform leafminer; another orchard was infested with P. crataegella (Clemens), the apple blotch leafminer; and both leafminer species were found at a fourth orchard site. The major parasitoids attacking the leafminers at all orchards were the ectoparasitic eulophid Sympiesis marylandensis Girault and the endoparasitic braconid Pholetesor ornigis (Weed). Data from sticky traps revealed four distinct flight periods of adult leafminer (spring emergence and three summer) each year, producing four generations (three complete summer and a partial fourth [fall overwintering] generation). Mean leafminer density (mines per leaO increased throughout the season. P. ornigis had four to five distinct adult flight periods, and S. marylandensis had five to six adult flights each year. Peak spring emergence of overwintering S. marylandensis and P. ornigis occurred, on average, 1.5 and 4.5 wk, respectively, after peak adult leafminer emergence. At half of the orchards examined, levels of percentage parasitism declined from the first to the second generation, increased from the second to the third generation, and then declined again from the third to the fourth generation.