Colorado potato beetle. Credit: Sam Schipani / BDN

In addition to the usual summer pests that always seem to plague Maine gardens, thrips, potato leafhoppers and Colorado potato beetles are thriving this growing season, much to the irritation of growers throughout the state.

Although this year’s pests have been “fairly normal,” the season started with exceptionally good conditions for thrips, said Caleb Goossen, organic crop and conservation specialist at the Maine Organic Farmers and Gardeners Association. Thrips are miniscule, needle-shaped insects whose impacts are most easily noticed on plants’ leaves.

“I’ve seen some cases of very high thrips populations, which can go unnoticed for a long time,” Goossen said. “By the time they’re noticed they can cause a lot of damage, particularly in onions. Symptoms like curly distorted growth, or leaves with white and black speckled sections are an indicator to look to new growth and emerging leaves to check for thrips and thrips larvae.”

Regularly pruning parts of the plant that have been impacted by thrips will help to manage the population.

Maine gardeners have also been experiencing an abundance of leafhoppers and Colorado potato beetles, both of which Griffin Dill, integrated pest management specialist at the University of Maine, called “a headache for gardeners.”

“Potato leafhoppers don’t overwinter in Maine and must blow in on winds from the Gulf states every year,” said Jim Dill, pest management specialist at the University of Maine Cooperative Extension. “They usually start arriving in late May or early June and work their way northward in the state. Some years we may not have them or maybe low populations. So scouting your garden is key, especially beans, strawberries, apples and, of course, potatoes.”

Goossen said to look out for distorted leaf growth and “hopperburn,” or the browning or shriveling of foliage that can often be mistaken for disease or nutrient deficiency.

Once you begin to see the bright green to yellow nymphs you can spray with an organic fungus suspension containing Beauveria bassiana, insecticidal soaps or pyrethrin or use floating row covers, Jim Dill said.

For Colorado potato beetles — which often prefer eggplant to potatoes, despite their name — covering your potatoes with row covers is essential, Jim Dill said.

“If you defeat the first generation of emerging beetles, you’ve won 90 percent of the battle,” he said. “Even though the beetles can fly, they most often walk from their overwintering areas to their potato host.”

If you do see full-grown Colorado potato beetles, with the orange-yellow bodies and distinctive brown stripes, despite your best efforts, Jim Dill said to check daily for the yellow and orange egg masses on the underside of leaves and squish them. For the ones you miss, he recommends organic sprays like Spinosad, NEEM oil and Bt.

“The final method is to buy an inexpensive hand vacuum cleaner and use it for this only — go out and actually vacuum the [Colorado potato beetles] off your plants,” Jim Dill said. “This seems to be especially attractive if you have young children — they seem to love to vacuum the beetles.”

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