Japanese beetle adults (Figure 1; JB) are out and about, feeding and mating on many different fruits, vegetables, field crops, and ornamentals. Numbers have been increasing steadily at my house in Monona and where I handpick them daily on my Honeycrisp apple trees, Somerset grapevines, cotton easters, arborvitae, etc… They are slowly showing up at the West Madison Ag Research Station vineyards and will continue to be coming into vineyards and other crops for the next couple of months. Our previous results show that they are active in vineyards from the end of June until approximately the third week of September in Wisconsin (Fig 2; Left panel 2017, right panel 2018) so we have a long battle ahead. I suspect this year may be a heavy year for Japanese beetles due to the mild winter temperatures and good snow cover overall, the wet spring, and the warm temperatures. Time will tell but we are off to a good start (for JB anyway!)
As mentioned in the last issue, grape plants can tolerate a fair amount of defoliation without any impact on plant growth or fruit quality. For grapes, 30% defoliation is used as a threshold for implementing chemical control. Mentioned in the last issue are the following chemical products that are efficacious at controlling JB adults: organophosphates (e.g., Imidan), carbamates (e.g., Sevin), pyrethroids (e.g., Danitol, Baythroid, Mustang Maxx), diamides (e.g, Altacor, Exirel), and neonicotinoids (e.g., Assail). Organically-approved insecticides include the insect growth regulators and repellents Neemix or Azadirect, the kaolin clay Surround as a repellent, the soil born bacterial insecticide BeetleGone!, and pyrethrum (Pyganic).
For more in depth information on the biology and management of Japanese beetle, please visit our You Tube channel and watch the webinar on “What to do now in the vineyard: post bloom”. You can view other videos there, including an interview on Asian Giant Hornet. Other than JB at this time, there are no other insect to worry about at this time. Wasps will start building up soon and we will talk about wasp management as well as other insects to think about at harvest time in an upcoming issue as well as in a grape webinar on July 29, 2020.
Thanks to Beth Workmaster for scouting at WMARS.
Happy growing season!This article was posted in Grapes, Insects and tagged Grapes, Japanese Beetles.