Sticking the landing, post-harvest psylla populations

by Chris McCullough, Robert Orpet, Molly Sayles, and Louis Nottingham

November 7, 2022

  • During the 2022 pear growing season, our WSU pear entomology team monitored pear psylla and its natural enemies (predators and parasitoids) across orchards in the Wenatchee Valley.
  • Orchards were either conventional, organic, or followed our new phenology-based Integrated Pest Management (IPM) program (detailed in this link: All programs experienced highs and lows in terms of pear psylla.
  • Conventional had great control of pear psylla during summer. However, as harvest approached, the elimination of natural enemies resulted in pear psylla nymph populations dramatically increasing (Figure 1).
  • Meanwhile, in organic and IPM orchards, natural enemy populations increased and kept pear psylla nymph abundance lower than in conventional orchards (Figure 1).
  • These differing scenarios meant a tradeoff between early-season damage in IPM and organic orchards vs. a sticky harvest and the risk of late-season damage in conventional orchards.
  • We evaluated damage in the field, and pear psylla marking downgrades averaged out to be similar between IPM and conventional orchards.

Read the whole article on the WSU Tree Fruit site.

Figure 1: Summary graphs of the average number of pear psylla nymphs, adults, and natural enemies from the beginning of August until mid-October at fields that practiced conventional, IPM (“Pheno” = phenology-based IPM guidelines), and organic psylla management.