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Connecticut Garden Journal: How to keep potato beetles from ruining your harvest

Leptinotarsa decemlineata (Colorado potato beetle) crawls near eggs on a sheet of potatoes.
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A Colorado potato beetle crawls near eggs on a potato leaf.

Potatoes and eggplants are fun vegetables to grow in Connecticut gardens, but as they start putting on growth you may notice someone else is interested in your plants. Adult potato beetles are large black and tan striped beetles that are active now, laying yellowish-orange eggs on the undersides of leaves. Potatoes and eggplants are their favorite plants to attack, but you'll see the beetles on other night shades such as tomatoes, peppers and petunias, too.

The eggs hatch into small, reddish, soft bodied larvae that start feeding. It's this stage that does most of the damage. While potatoes can lose up to 1/3 of their foliage and still produce a good crop, eggplants and other night shades can be seriously damaged by these beetles.

Luckily, there are a number of things you can do. The simplest control is to check the leaf bottoms every few days for the eggs and crush them. This will stop the potato beetles in their tracks. You can also hand crush the larvae, but wear gloves. It will get messy. Adult beetles are hard to kill with sprays, but the larvae are susceptible to an organic Bacillus thuriengensis or Bt spray, specially formulated for potato beetles. Spray in the evening on just the infected plants, when the larvae are still small, to be most effective.

There are some fun home remedies you can try like using a shop vac to suck the larvae off the plants and planting tansy or catmint around potatoes as companion plants to mask the scent of the potato from the adult beetles. Rotating crops every year helps as well.

Charlie Nardozzi is a regional Emmy® Award winning garden writer, speaker, radio, and television personality. He has worked for more than 30 years bringing expert information to home gardeners.
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