By Nebraska Extension Horticulture Educator Kathleen Cue
The most important thing to understand about Japanese beetles is their feeding doesn’t kill trees, shrubs and flowers. Granted, it isn’t fun to see the lacy leaves they’ve created, but pesticide management options require thought and planning before you set out for revenge.
Systemic insecticides, for instance those containing the active ingredient imidacloprid, are taken in by plant tissues. Systemics may have a label for application to trees and shrubs but before these are used, the applicator should make sure the plant is past its flowering stage in order to protect pollinators. Also, a systemic product can never be used on linden trees.
Topical insecticides with the active ingredient bifenthrin or carbaryl are those that coat plant tissues so Japanese beetles ingest the toxin when they eat. As you would guess, topical insecticides can wash off in a rainstorm, so using a product called a spreader sticker will help. Again, it’s important that topical insecticides are not sprayed on flowers in order to keep pollinators like bees and butterflies healthy.
Remember that Japanese beetle traps are too good at what they do—attracting Japanese beetles. Research indicates there is more Japanese beetle damage in yards with traps than those without. While Japanese beetles are accomplished at eating, they are uncoordinated at flying. Any beetles that bumble past the traps will be diverted to nearby plants where they begin feeding.
Japanese beetles love fruit, so keeping them away from your prized peaches is a problem. There are fruit bags, made of fabric, mesh or nylon, that individually protect fruits from any bug onslaught. Kaolin clays can also be sprayed on fruits and act as deterrents to insect feeding.
Where practical, picking Japanese beetles off plants is very effective and doesn’t cause harm to pollinators. The best time of day to do this is at 7:00 in the evening. Instinctively, Japanese beetles drop when the plant they are on is disturbed. You can use this instinct to your advantage by holding a small bucket of soapy water beneath a branch, giving it a light tap and watching as the beetles drop into the bucket. Satisfaction and clean-up in one step!
More information can be found here: https://extension.unl.edu/statewide/douglas-sarpy/pdfs/ce/resources/ce-dealing-with-japanese-beetle.pdf .
The Extension Master Gardener horticulture helpline and open clinic hours are:
- Mondays, 9:00 am to 12:00 noon, Washington County Extension, 402-426-9455
- Tuesdays, 1:00 to 3:00 pm, Cuming County Extension, 402-372-6006
- Wednesdays and Fridays, 9:00 am - 12:00 noon, Dodge County Extension, 402-727-2775
Japanese Beetles
Fruit Bags for Fruit Trees
Tree Pest Detector Workshop
The Nebraska Forest Service will be hosting a Tree Pest Detector Workshop on July 18, from 1:00 to 4:00 pm at the Dodge County Extension in Fremont. Participants will learn how to detect emerald ash borer, thousand cankers disease of walnut, and other invasive tree pests. Topics will include: signs and symptoms of pest infestation, tree identification, and survey reporting. In exchange for the training, participants will pledge to provide three hours of time in pest survey activities. Who should register: Green industry professionals, natural resource professionals, Master Gardeners and other volunteers with at least a minimum knowledge of trees and their pests.
Location: Dodge County Extension, 1206 West 23rd Street, Fremont, Wednesday July 18th, 1:00 to 4:00 pm
REGISTER AT: https://www.eventbrite.com/e/tree-pest-detector-workshop-fremont-registration-47097952243?utm_term=eventname_text
Registration is limited to 25 participants. Deadline to register is July 16.