There are thousands of species of beetles in Maine, but just a few of them could cause big problems in your garden this year.
Simple methods like the soapy water trap, protecting young plants with row cover, rotating your planting sites and disposing of eggs before they hatch can help you protect your plants at a low cost.
Some farmers also plant other crops the beetles like next to the ones they want to protect, a method called perimeter trap cropping.
Whatever you choose to do, knowing how to identify these common Maine beetles emerging right now is a good first step. The free online New England Vegetable Management Guide is one simple, updated resource for information on any of these insects.
Colorado potato beetles
These round, striped yellow beetles also happily chow through eggplants. Look for their bright orange eggs on the undersides of leaves. Crush them or tear that part of the leaf off. Doing this now reduces the number of adult beetles you’ll see in August.
Mulching with straw has been proven to reduce beetle presence. Other insects, like 12-spotted ladybugs, are known predators of the potato beetle in all its life stages. Row covers on the seedlings until about the time they flower can also protect the young plants.
In future seasons, consider planting your crops in different areas each year, at least 200 yards away from where they grew the year before. Planting early or late with seed varieties that can handle the adjustment could also help you avoid the beetles’ adult stages.
Striped cucumber beetles
Cucumber beetles have yellow stripes like potato beetles but longer bodies. You may find them on any plant in the cucurbit family, including your pumpkins and squash. As the season begins, these beetles can lead to reduced yield or slower growth. They also spread bacterial wilt, which could wipe out a crop.
Light row cover until the plants begin to flower is also an option here. For beetle-heavy areas, the Maine Organic Farmers and Gardeners Association suggests hand-pollinating the plants and continuing to leave them covered with netting as they grow. When the plants are established, they’ll be in less danger of wilt.
Some Maine homesteaders use yellow sticky traps, which are a similar color to cucurbit flowers, or yellow bowls filled with soapy water. The beetles can also be collected by hand or even vacuumed.
Japanese beetles
These shiny green and copper beetles eat more than 400 different crops and might be found anywhere in your garden, though they particularly like fruit plants. If the leaves of your plants have lacelike holes, these beetles are probably to blame.
Knocking them off of plants each morning or evening into a bucket of soapy water is a common management method. If you try to pick them up, they’re more likely to fly away, so pushing them is the way to go. Some people believe the smell of dead beetles from a bucket left outside will keep other adults away.
Row cover or netting is also useful. Milky spore and nematode treatments have been successful for some gardeners.
Pheromone traps can draw in new beetles from miles around, according to the University of Maine Cooperative Extension. If you try it, place the trap away from your beds.
Mexican bean beetles
These aren’t as widespread as some other beetles, but when they appear they’re likely to be a regular problem. Shaped almost like the beans they eat, the beetles are small and brown with black spots.
Their eggs, laid on leaves, are small and yellow. If you don’t catch the eggs in time, introducing the predator wasp Pediobius foveolatus is one biological control method to purchase. Next year, rotating the site of your bean planting can help you.
Flea beetles
There are many types of flea beetles, and some of them are likely to leave tiny holes in the leaves of your plants. They’re often found on brassica plants like broccoli. Rotating your bed sites can help. Row cover is also a common method of controlling these beetles, but make sure the cover is sealed so the small bugs can’t get in.
Bonus pest: squash bugs
While not a beetle, these common bugs cause similar problems and acting now can protect your crops later. Come late summer and fall, they might do some serious damage to your pumpkins, plus squash and cucumbers. They suck sap from the plants and often leave wilting disease behind.
Right now, look for their coppery, shiny eggs on the undersides of leaves. Tear that part of the leaf off and either crush the eggs or drop them in soapy water. If you find the nymphs or adult bugs later in the season, manually squashing them (they smell, but you’ll survive) can make a difference in small gardens.
