Biology of the reemergent pest apple flea weevil, Orchestes pallicornis Say, and methods for its organic control

The goal of this research was to explore the basic life-history and seasonality of O. pallicornis, and provide effected growers with OMRI-approved tactics to control it. I conducted beat sampling and leaf collections throughout the growing seasons of 2011 and 2012 at three Michigan orchards to identify the seasonality of O. pallicornis adults and larvae. O. pallicornis adults are active in the early Spring, timed with the Green Tip or Tight Cluster stages of apple bloom phenology. The number of larval instars was determined (3) by measuring the head capsules of field-collected larvae. Parasitoids of O. pallicornis were studied through observation of field-collected larval mines stored in petri-dishes. At least five families of parasitic hymenopterans were found to parasitize O. pallicornis. I tested conventional and organic insecticides against O. pallicornis adults in a lab bioassay. Conventional products all caused high O. pallicornis mortality. Entrust (Spinosad) was the only tested OMRI-approved product to cause high mortality. I then conducted field insecticide trials emphasizing Entrust to determine appropriate management practices. Entrust applied at Tight Cluster is suggested for control of the economically damaging Spring adults, due to reduced potential for parasitoid toxicity and high pest mortality. Half-rate applications of Entrust may be sufficient to control adult populations, especially those of the Summer generation. This information was synthesized into an extension bulletin for distribution to afflicted growers.