David Owens, Extension Entomologist, owensd@udel.edu
Vineyards
Grape root borer has begun emerging from the soil! If you have pheromone traps or mating disruption or both, deploy them ASAP. Start scouting at the end of next week for pupal cases around the base of the vine sticking out of the soil. The old threshold when Lorsban was labeled was 5% of vines with a pupal shed. If you reach that, it means that next year we will need to take remedial action. The only thing labelled now is CBC America’s resurrected mating disruption Isomate GRB. It will come in packs of 100 twist ties that can be tied on a trellis wire throughout a block, one pack should treat an acre.
Japanese beetle activity has increased sharply over last week. Grapes can tolerate 30% defoliation, and beetle feeding tends to look worse than it actually is. However, Japanese beetles also have a tendency to aggregate in spots and on certain varities over others. Curiously, pyrethroids are not labeled for Japanese beetles in grapes, but they are for other crops. University of Georgia’s Brett Blaauw has an excellent article on beetle management including efficacy ratings here: https://viticulture.uga.edu/2017/06/japanese-beetle-management-in-vineyards/.
Cherries and Plums
Asiatic garden beetle is active, and this insect loves cherries and plums. It feeds at night but hides in the soil during the day. It is voracious on cherry. Look for leaves with narrow, rectangular holes eaten out of the leaf margin going inward to the blade’s midrib.
Stone and Pome Fruit
Continue monitoring for stink bugs and for first generation plum curculio. Wild cherry is about to ripen, and this is often a good trigger for stink bugs to move around. Some of our blacklight traps have been picking up high numbers of green stink bug and brown marmorated stink bug. Trap counts can be found on the UD Insect Trapping Program webpage.