REGION — Farmers and home gardeners should be aware of invasive insects being found locally that could impact crop yields and decisions on what to plant.
In 2019 Swede midge was found in a farmer’s broccoli fields in Farmington. A member of the fly family, it feeds on broccoli, cabbage, cauliflower, Brussels sprouts and other members of the Brassica family.
Once established Swede midge is difficult to get rid of. Native to Europe and southwestern Asia, the insect was first discovered in Canada in 2000 and in New York in 2004.
Swede midge is a new invasive insect found in Farmington in 2019. The larvae, shown in the circle in this photo affects broccoli, cabbage, cauliflower and similar plants. Dave Fuller
“They have only been found in Franklin and Aroostook counties that we know of,” UMaine Cooperative Extension Agriculture and Non-Timber Forest Products Professional Dave Fuller said in September 2019. “Aroostook has thousands of acres of brassicas. They’re a big crop there.”
The adult fly is about two millimeters in size. The larva, or maggot, is what causes the damage.
The smallness of Swede midge flies is seen in this trap marked off in one-inch squares. Dave Fuller
“Swede Midge has not appeared to have traveled from the farm where it was first observed two years ago, though it has a persistent presence on the affected farm,” Fuller wrote in a May 14 email. “Pheromone trapping in the area will continue to detect the spread of the pest.”
For organic growers, Fuller noted the only effective measure is to practice crop rotation as far from a Brassica planting the year before as possible and to use protective crop cover to keep the flies out.
“Other farms can use synthetic sprays which offer good control of Swede midge though pheromone trapping should be practiced to detect the first flights of the midge,” he continued.
When asked about other invasive insects, Fuller indicated Spotted lantern fly and marmorated stink bug are not in the area yet.
Leek moths are another invasive insect farmers and home gardeners should be on the lookout for. The larvae destroys leeks, but can also cause damage to onions and garlic. Dave Fuller
“Leek moth has shown up in the Rangeley area and is slowly moving around there,” he wrote. “Leek moth only affects all alliums but prefers leeks the most (destroys them!) but makes a mess of onions and can get into garlic bulbs. Only the larvae cause damage but there can be quite a few of them over the 4 generations in a season.
“The moths have already been out for about 2 weeks,” he continued. “Crop rotation along with row covers work the best as the larvae hatch and enter the plant material where non-systemic sprays can’t reach them.”
Another invasive insect, Spotted Wing Drosophila (SWD) were captured in Maine for the first time in fall 2011. It is a concern for growers of raspberries, blueberries and day-neutral strawberries, as well as many other soft fruits.
Spotted Wing Drosophila can cause damage to berries, soft fruits and some vegetables. File photo
This small fruit fly lays its eggs in fruit before it ripens, resulting in fruit that is contaminated with small white larvae just as it is ready to pick. As a result, the fruit quickly rots and has no shelf life.
“Some farmers have abandoned crops like fall-fruiting raspberries due to the heavy pressure from SWD,” Fuller wrote. “Others have planted earlier-bearing highbush blueberries that fruit before the SWD numbers build to a critical mass. Sprays approved for use on SWD are effective but require frequent sprays.”
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