David Owens, Extension Entomologist, owensd@udel.edu
Plum curculio is active. Be on the lookout for crescent-moon shaped oviposition scars on fruit. While adults are active and fruit needs to be protected soon after petal fall and peach shuck split, cool weather has slowed them down a bit. Activity is increasing and going to increase further with warm weather in the forecast. Michigan State has a good article eon effective insecticide options here: https://www.canr.msu.edu/news/plum_curculio_management_in_stone_and_pome_fruits. In addition to the organic options described, organic producers and smaller plantings can be protected by bagging fruit. University of Kentucky has an excellent article on fruit bagging: https://kentuckypestnews.wordpress.com/2020/05/12/bagging-fruit-for-disease-and-insect-management/?utm_source=KY+Pest+News+List&utm_campaign=26775c4cc3-KPN_NEWSLETTER_EMAIL_CAMPAIGN&utm_medium=email&utm_term=0_bee884adb8-26775c4cc3-228242837&ct=t(RSS_EMAIL_CAMPAIGN). Be sure to treat the fruit with a fungicide and insecticide (if at all possible) before bagging fruit.
Plum Curculio damage on plums. Note the crescent shaped egg laying scar.
Plum Curculio damage on plum fruits. Feeding injury consists of small round openings in the skin extending about 1/8 inch into the fruit.