In 2018, the Bangor Daily News predicted that
leek moths would spread to Maine. That forecast came true.
“It’s a similar story to the swede midge,” Goossen said. “It was also introduced into Canada and has been spreading.”
Goossen said that leek moths feed on allium species, such as onions, garlic, shallots and — of course — its eponymous leeks.
“[The moths] lay their eggs on the crop and then the egg hatches and the larvae emerge,” Goossen said. “It’ll burrow inside that hollow leaf and eat the inside, leaving just the outside waxy skin, [like] windows in the onion leaves. Leeks and garlic don’t have hollow leaves, so they feed on the upper surface.”
To manage leek moths, Goossen suggested excluding adults using row cover so they cannot lay eggs.
“The moths only fly at night so if you wanted to weed things, you can leave your onions uncovered all day long and just make sure you put the cover back on before night,” he said.
Regardless, growers should expect more leek moths in the years to come.
“It seems like the leek moth maybe likes river valleys, may follow the rivers down through the state,” Goossen said. “There’s a progressive expansion of territory. For both [swede midge and leek moth], modeling of climate factors and what might be suitable habitat [show that] all of New England falls within suitable habitat and beyond.”
Browntail caterpillars and moths
Browntail caterpillars are an invasive species that have long plagued the coast in Maine, but experienced a comeback in 2019.
“Some of its natural enemies were introduced by government agencies a long time ago [that] suppressed them for a long time but for whatever reason has gone through a sudden resurgence,” Murray said. “It doesn’t show much sign of slowing down.”
Browntail caterpillars do moderate damage to crops — Goossen said they defoliate fruit trees, especially apple trees — but they are most irritating to the gardeners themselves because of their
irritating hairs that cause a poison ivy-like rash.
“[The rash] lingers for weeks at a time,” Murray said. “It can cause respiratory problems [and] exacerbate asthma.”
Moreover, the browntail’s range continues to expand.
“It did sound like a lot of places are seeing browntails where they didn’t have it previously,” Goossen said. “It continues to spread.”
Goossen said row cover will help reduce browntail numbers, but the population will mostly depend on how many overwintering larvae were able to survive the winter and whether diseases will impact the population boom.
“There is a pathogen that kills it,” Murray added. “We were kind of hoping that this last year would be a little less because it was such a wet spring and summer, but it was not enough to make a difference.”
Credit: Courtesy of David Handley
Spotted -wing drosophila is a pest that’s been causing damage to Maine fruit crops for close to a decade and one to keep an eye on in 2020, according to Kirby, the insect diagnostician with University of Maine Cooperative Extension.
The spotted-wing drosophila is different than the common fruit fly found in kitchens and pantries. This strain of fruit fly is native to northern Asia and was first seen in Maine in 2011. Common fruit flies feast and multiply on over-ripened fruit, but the spotted-wing drosophila targets soft-skinned fruits before they are ripe. In Maine, that’s bad news for late season fruits such as raspberries and strawberries.
“[It’s] a little more aggressive in that it can lay its eggs in fruit that haven’t started rotting,” Goossen said. “Fruit flies need a fruit to be decaying, but this one can puncture the skin and lay its eggs.”
Infestation can happen quickly, because one female fly can lay up to 400 eggs. The eggs only need between 10 and 14 days to become an egg-laying adult itself. It can take very little time for millions of the flies to be in a berry crop and begin feasting on the ripening flesh of the fruit.
Though this year’s strawberry season was
shorter than usual, Murray said it continues to be a pest of berries, especially raspberries and late-season blueberries.
“It may be showing up more and more with a warmer climate,” Goossen said. “It takes a while for the population to build up enough to be a real problem. If it’s a warm spring, they will probably get a jumpstart and build up their numbers faster.”
Credit: Courtesy of Angela Yuriko Smith
Cutworms are a scourge for home gardeners and commercial farmers alike. The turnip moth larvae emerge in the spring, hiding under litter or soil during the day and sneaking out in the dark to feed. Though there are several different species of cutworms with different habits, the larva typically attacks the first part of the plant it encounters — often, the stem of a seedling.
“They [usually] cut plants off at the base,” Murray said. “You go out and all of a sudden see a bunch of plants laying on their sides.”
Goossen received more reports of cutworms in 2019 than usual, especially in Waldo County, but the distribution was scattered.
“A lot of people saw damage, [but] some people will not see any and other folks will see huge numbers of cutworms that take down everything they plant,” Goossen said.
Murray said that growers of certain crops had more problems with cutworms than others. There are several species of cutworms, she explained, and their prevalence can be spotty from year to year. One crop that particularly suffered was hemp.
“Hemp growers, one of our newest crops in Maine, had a real terrible time with cutworms,” Murray said. “It was not a cutworm that cuts the plant at base, but [one that] goes up in the flower in portions of the plant. It ruined the quality [of the hemp].”
When it comes to what growers can expect in the upcoming year, experts agree that predicting pests year to year is challenging because of the number of variables involved. Kirby said it’s difficult to predict the levels and range of these pests in Maine for the coming year, as populations depend on many variables, including weather conditions, pesticide applications, predators, parasitoids and diseases.
Goossen said gardeners should watch the winter to come — a tough winter with freezing a thawing and long cold spells without snow could kill overwintering pests — but even that is hit or miss.
“It’s always hit or miss,” Goossen said. “Sometimes you see the weather and you think you can make an assumption on that but it surprises you anyway.”