Asiatic garden beetles
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.0 thumbs up!Posted almost 3 years ago
Well, you’re in the right part of the States. Down south, they can have two hatches a summer. Here in the northeast it’s one per year, so every one hand picked helps.
When you’re trolling thru the soil, if you come across any white gelatinous masses, toss them in the soapwater, too. They’re egg masses.
I may be wrong, but I don’t think milky spore would be effective because milky spore specifically targets japanese beetles… but they’re both species of scarab beetles so… dunno for sure.
Neem oil – yeah, but not so much, really. Pyrethrins would probably be more useful. They break down pretty quickly in oxygen or light – which, I think, is exactly what you’re looking for. Applied in late evening after all the bees go to bed for the night (because it’s extremely toxic to bees) paying particular attention to the underfoilage that they would contact first will most probably be a good “first strike”. :-)
Take extreme care when handling pyrethrin – you might think it’s just an extract of mums (which it is), but it can mess you up BAD if you get enough on you. Even a little can be enough to cause burning, itching, headache, asthmatic symptoms… to name a few. It’s toxic to people, pets, bees and fish.
Light traps = bug zappers. Like June bugs – who are cousins – they’re attracted to bright light and have been found in blacklight traps, but I don’t know if one works better than the other. ZZZZZTT!!! And another one bites the dust. ;-)
0 thumbs up!Posted almost 3 years ago
Thanks, Paul! I don’t remember finding any white gelatinous masses, but now at least I know to look out for them. I transplanted my basil and pineapple sage – the beetles’ favorites – into containers and moved them away from the rest of the garden last week before I went on vacation for several days. When I got back, I checked the dirt in the containers and the garden and didn’t find any beetles. :-) I have to go out tonight after dark and see how many are still about.
0 thumbs up!Posted almost 3 years ago
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