Here on our small farm, we love our small flock of chickens – their delicious and healthy eggs, their comical antics and their expert bug control are all reasons why we’ll always keep a few chickens around. One additional bonus? Chickens LOVE to eat Japanese beetles!!!
Anybody who gardens in New England is almost definitely familiar with the damage that Japanese beetles can do to plant foliage and lawns. Their grubs (juvenile form) eat plant roots and wreak havoc on the shallow roots of chemically-treated lawns.
The frustration for gardeners and landscapers is that Japanese beetles are not simple to control. Because they are an imported pest, very little local wildlife are adapted to use them as a food source and they have few natural enemies to keep their numbers in check. Even if you spray all the grubs and beetles dead with a toxic concoction, very soon they will be back, usually arrived from neighbors’ properties. It’s not worth it, especially because the poisons also kill the beneficial insects that you want to encourage.
The encouraging news is that natural predators of Japanese beetles introduced by biologists do appear to be having an impact on their populations. Parasitic wasps and microscopic nematodes attack beetle grubs during the time they spend in the soil. A parasitic (tachinid) fly imported from Japan by biologists targets the adult beetle and does appear to be having an impact on breeding populations. I don’t think we’ll ever see Japanese beetles disappear completely from our landscape, but from these natural controls I do notice fewer beetles each year in the gardens of central Massachusetts.
In the picture below, the Japanese beetle on the left has a white dot on its thorax (behind its head), which is the egg of the parasitic tachinid fly. Many beetles will “wear” multiple dots. These eggs hatch into larvae that burrow into the beetle and consume its tissue from within, eventually killing the beetle within 5-6 days. Don’t kill these beetles! You want the eggs to hatch and the fly to complete its life cycle to continue its work on beetle populations.
So what can you do if a favorite plant is swarming with adult beetles? The least-impact method of controlling adult Japanese beetles is manual removal. In the morning when the beetles are lethargic, sweep them (with your fingers or a small brush) right off the foliage of infested plants into a jar of water. They will thrash around in the water but can’t fly away. You can then flush them down a toilet or, if you have a chicken coop, throw them into the coop! Your chickens will go crazy for them! Because adult beetles lay eggs in the soil where they mate and feed, the more beetles you can remove from your property during their mating stage, the fewer grubs that will hatch out into beetles next year.
My hens Millicent and Betty follow me around during my “beetle sweeps” so they can gobble the beetles right from my collection jars:
As for grubs (the juvenile form of the Japanese beetle that eat grass roots), avoid at all costs the chemical grub control based upon Imidicloprid (sold in the US by the trade name Merit) a chemical that’s been banned in several European countries due to links between its use and the collapse of honeybee populations (aka Colony Collapse Disorder). If parts of your lawn are dying and you suspect grub damage, your lawn is under stress and chemical treatments will not fix the problem. You can try applying beneficial nematodes (microscopic wireworms) to attack the grubs in the short term, but longer term, if you convert to an organically-maintained lawn where grass roots can grow deep into the soil, the impact of the grubs will decline. And, supply suitable habitat for ground-feeding birds and the parasitic insects, and let them do their thing. It’s healthier for your lawn, your family, the bees and the planet.
To support those tiny parastic flies and wasps, make sure you have lots of nectar plants blooming to supply the sugary substance these beneficials need to fuel their flight. Without nectar when they need it, they won’t stick around. Pictured below are New England native plants boneset, Joe Pye weed and goldenrod blooming in late summer: