I went out after dark with a flashlight last week to pick some lettuce for a late-night dinner, and discovered a host of beetles eating my pineapple sage. Some online research identified them as Asiatic garden beetles, and I’ve been battling them ever since.

This is everything I’ve learned so far about them. If you have any additional information about them, especially how to control them, please share it!

Asiatic garden beetles look similar to Japanese beetles, but they’re a little smaller and a warm medium-brown color all over. The eggs are laid in the soil during the summer and overwinter until they hatch into grubs in spring. The eggs need moist soil and will die during prolonged dry spells, so not watering the lawn helps control their population. The grubs are white and curled up and fall into the category of “white grubs.” They feed off of the roots of grasses and weeds during the early spring, so keeping a weed-free garden is important to limiting their food supply. The grubs turn into beetles in June and immediately start working on making more beetles.

The beetles are nocturnal and burrow into the soil during the day, so it’s easier to find them at night with a flashlight. I can easily collect 30-50 off my plants and the grass around the garden (dropping them into soapy water to kill them). They don’t bite or sting or move very fast, so at least they’re easy to pick up. I can also catch them during the day by finding plants that have been badly eaten and raking my fingers through the top inch of soil around their stem. They seem to gather in groups, so I usually turn up several at a time. I’ve also noticed that they will emerge from the soil when the soil they’re in is flooded, so heavy watering may help control them. I’ve also read that they’re attracted to bright light and found a reference to “light traps,” but nothing specific. If anyone has any info on how to build a light trap, please let me know!

I don’t think I’m making much headway against them with the individual picking method, so I’ve been researching other control methods, though I haven’t tried any yet. I’m focusing on organic methods. The best option may be milky spore disease, but it takes 2-4 years to build up a sufficient level to control the beetle population. (And you can’t use insecticides during those years, or you’ll kill the milky spore disease!) Some sites say insecticidal soap, such a Neem oil soap, is effective against the adults. Parasitic nematodes – especially Steinernema scarabaei – are effective against the grubs, although I can’t find any available commercially. Heterorhabditis bacteriophora and parasitic wasps are less effective, but available for purchase.