Close-up of a lettuce aphid. Credit: Stephen Ausmus / U.S. Department of Agriculture's Agricultural Research Service

The beginning of the gardening season is thrilling for new and experienced gardeners alike. However, it is also a time when tender seedlings can be extra susceptible to pests. Inexperienced gardeners in particular may not recognize that there is a parasite in their midst until it is too late. 

Here are the early pests to watch out for in Maine and how to take care of them, whether you are open to using pesticides or prefer to address pests without the use of chemicals.

Lettuce aphids, Nasonovia ribisnigri, infesting a lettuce leaf. (Photo by Yong-Biao Liu, courtesy of the U.S. Department of Agriculture’s Agricultural Research Service)

Aphids

Jim Dill, pest management specialist at the University of Maine Cooperative Extension, receives calls throughout the gardening season about pests and how to address them.

“Probably the number one thing I’ve been getting calls on [recently] is aphids,” Dill said. “They seem to be pretty prevalent on everything from ornamentals to garden plants.” 

In most cases, aphids cause little or no damage to the health of plants as they feed on them, but large populations can stunt the growth of a plant and cause parts of the plant to die. 

Gardeners can often see the tiny insects in clusters on the stem or the underside of the leaves, Dill said.

“If they’re in a really big concentration, the leaves will start to curl,” he said. 

Aphids may also cause a black sooty mold on the top of leaves. The bugs secrete a sugary liquid called honeydew, which can cultivate mold as it accumulates. 

In order to address aphids, Dill said that gardeners can use an insecticidal soap, but one of the most effective ways to address the issue is to hose them off.

“It washes the honeydew off, so that takes care of the sooty mold,” Dill said. “It also washes the aphids off. If they get washed off sometimes, they can’t just climb back up and get to the plant where they were to begin with.” 

Flea beetle, Trachyaphthona sordida. (Photo by Peggy Greb, courtesy of the U.S. Department of Agriculture’s Agricultural Research Service)

Flea beetles

Another pest Dill said he has seen prevalently this growing season is flea beetles, particularly on cole crops like cabbage and broccoli.

“They’re usually a dark color. [It’s] a tiny beetle that, when they’re disturbed, they jump,” Dill said. 

For the most part, the larvae of flea beetles are root eaters, which can tunnel into the roots and cause problems with the plant, Dill said. Once they are mature, they will begin munching on vegetation. 

“If you look [and you have] lots of flea beetles putting pin holes in the leaves, it’s something that’s worth trying to manage,” he said.

Dill said the best way to address flea beetles if you see this damage is to use a pesticide product that contains spinosad, a natural substance made by a soil bacterium that can be toxic to insects. 

Imported cabbageworms

Another pest that is ravaging cole crops this season is the imported cabbageworm. The pest is perhaps better known for its tiny but ubiquitous white butterfly.

“That’s the first butterfly you see,” Dill said. “I’ve been seeing them since April. Flitting around, waiting for you to put your transplant in.” 

If the chunky green worms have found their way to your plants, you will see large, ragged holes in the leaves.

“They’re bigger holes, whereas the flea beetles have a tendency to feed on the edge,” Dill said.

Dill recommended using Bt — Bacillus thuringiensis — if you spot cabbageworm butterflies in your garden. It’s a natural occurring, soil-borne bacteria that has been used since the 1950s for natural insect control. 

Gardeners can also use companion planting and other non-chemical strategies to attract helpful insects to your garden that will keep pests like imported cabbageworms at bay.

The larval stage of a cutworm. (Photo by Angela Yuriko Smith)

Cutworms

Cutworms are frequently a problem for gardeners in Maine. The brown grubs are hard to spot, but they will fell seedlings like timber by munching through their tender stems.

“They’re not very discriminatory worms,” Dill said. “Cutworms will attack a variety of crops: peppers, tomatoes, almost anything.”

Cutworms will hide under the soil during the day and come out at night to feed on seedling stems or climb up the plants to munch on vegetation.

“To look for them, you can move the soil around the base of the plant, all of a sudden you’ll find this caterpillar curled up in this little ball in the soil,” Dill said.

Effective cutworm collars can also be made from small yogurt cups with their bottoms cut away. (Photo by Reeser Manley)

Dill said that Bt will work for cutworms as well, but there are also simple non-chemical measures that can protect your seedlings. For instance, a protective collar around your plants will keep cutworms from chomping seedlings down at their base.

“If you’re having cutworm problems, an easy fix on that is to dig around the base of the plant a little bit, take a wad of aluminum foil and wrap it around the stem,” Dill said. “Some people use toilet paper tubes.”

A slug slids its way down a dew-covered tigerlily leaf Monday, June 29, 2009 at Swan Lake State Park in Swanville. (Bridget Brown | BDN)

Slugs

One pest Dill has been surprised to see recently is slugs. Despite the relatively dry growing season, he has received calls about slug problems in a few spots along the coast. 

“Normally in dry years the slugs have a hard time, [but] they’ve been out and about,” he said.

Slugs eat a wide variety of plants, from vegetables to ornamental plants. They will feed on foliage at night and hide under the soil or mulch during the day.  

“You’ll get up in the morning and the foliage is gone and there’s no culprit, [but] usually if you turn the leaf a little bit you’ll see a shiny slug trail,” Dill said. “That’ll be a tell-tale sign of a slug.” 

Dill said that commercially prepared slug baits will work well to manage slugs, as do homemade DIY traps using yeast or beer to attract the pests. You can also manage slug populations by managing debris around your garden.

“If you have a lot of things laying around the side of the garden for debris, they hide under those at night and crawl under the garden very slowly of course,” he said. 

Cucumber beetle. (Photo by Scott Bauer, courtesy of the U.S. Department of Agriculture’s Agricultural Research Service)

Cucumber beetles

Black-and-yellow striped cucumber beetles may not be out in full force yet, but Dill said that they are sowing the metaphorical seeds for their development later in the season. If your garden has had cucumber beetles in the past, you can expect to see them again. Dill said they are the type of pests that will overwinter and come back with a vengeance. 

“Cucumber beetles sit there and watch you plant your cucumber seedlings so they can jump right on them when you turn your back,” Dill said. “Sometimes as soon as you get the seedlings out sometimes they’ll destroy the seedlings. You want to make sure after you plant, go back a couple hours later and look and see.”

The adult beetles will feed on the leaves, but the larvae will feed on the roots and may transmit a bacteria that causes bacterial wilt.

“One day they’ll look fine, and the next you’ll come out and [your cucumbers are] all wilted,” Dill explained. “You think, ‘Maybe I have something boring in here,’ but no — it’s all gummed up with bacteria.” 

Once this happens, Dill said that the plants are effectively past the point of no return, so it is important to nip the problem in the bud early in the season. You can lay down traps to show that the bugs are there, but Dill said that spinosad is the best way to address them. 

No matter what, observation is essential when it comes to managing pests.

“You should go out there every day and look at things,” Dill said. “It seems like sometimes with them they do the damage overnight. Observation is the key.”