The Japanese beetles have descended upon us in full force. While most damage is just cosmetic, it is still disappointing to watch your favorite flowers get chewed alive by these metallic insects. There are countless methods that are claimed to be the answer for controlling these binging beetles- everything from knocking the beetles into soapy water, to just calling it quits on any plants they may find appealing. While both those methods are effective, we want to take some time to explain other options out there in combating this beetle battle.
Systemic insecticides could be considered the nuclear bomb of a beetle’s world. Imidacloprid or other neonicotinoids are the most guaranteed way to eradicate a beetle population. BUT it is important to mention that neonicotinoids do not discriminate, and they will kill any insect that feeds on it- including our beneficial bees. This doesn’t mean you have to stay clear if you have a heavy infestation of Japanese beetles. Just keep this in mind and do not use on or near pollinator attractive plant to minimize the danger to beneficial insects. Systemic insecticides are applied as a soil drench, trunk spray, or by professional injection. The plant takes up the chemical and creates a toxicity to beetles and other insects that try to feed on it.
Other insecticides that are not as harmful to pollinators, but still effective on Japanese beetles are Pyrethrins and Neem Oil. Pyrethrins work through direct contact, so avoid spraying when pollinators are present. Once sprayed, it provides some repellant effect, however it also breaks down quickly. Neem oil works by repelling and deterring Japanese beetles, and other insects. Neem oil is also considered non-toxic and can be used in organic gardening. There is a low risk to beneficial insects, but it may be necessary to reapply often to get desired results against Japanese beetles.
Physical Control Methods
If you would prefer to avoid all pesticide use, there are some physical control methods as well. Pheromone traps are frequently brought up, but there is some discussion over how effective they are. These traps release a scent to specifically attract Japanese beetles. The beetles enter the trap and are unable to escape. However, this has been found to attract more beetles to an area. If you decide to give pheromone traps a try, locate them away from susceptible plants. A physical barrier such as netting may also be used in lieu of chemicals. This netting only has to be in place when adult beetles are active, mainly in July and August. Keep in mind that netting also blocks pollinators from reaching your flowers, so do not use if your plants need pollination.
One other physical method of repelling Japanese beetles involves buying more plants! Try mixing in plants that are unfavorable to Japanese beetles to your landscape. Japanese beetles are less likely to feed on plants that have an unfavorable smell to them, such as Allium. Breaking up their buffet with unappealing plants may convince them to find somewhere else to snack.
At the end of the day, the method you choose will depend on your personal goals for your garden.