Pest Reports

The Pest Report is produced once every week or two during the growing season. It is a compilation of short discussions of pests and diseases either working the fields or soon to be seen. The discussions include biology of the pest organism, effects on the plant, and recommended solutions. Some of the pieces I write myself, some of them I pick up with permission from other crop advisors around New England and modify for organic growers. Often I learn about an approaching problem from folks in southern New England states where problems typically arise first, and I can pass on the warning to those of us up north anxiously awaiting arrival.
Many of the insects and disease are repeat offenders and appear every year around the same time. This is most commonly not a chance event. Rather, they have been holed up for the winter and somehow they receive a signal that it is their time to wake. Sometimes it is a chance event because some pests do not overwinter here and are simply at the mercy of the wind blowing them to our crops from the south or west. In any case, many of the articles may seem familiar because they, and the problems and solutions, are the same as last year. Many of the articles will be new because there may be some new solutions available, or sadly, because there are some new pests showing up in New England.

Read MOFGA’s Pest Reports Fact Sheet Series

PurpleBlotchOnOnion.EricSidemanPhoto

Foliar Diseases of Alliums

Disease(s): Common Foliar Diseases of Alliums This fact sheet discusses botrytis leaf spot (Botrytis squamosa), purple blotch (Alternaria porri), stemphylium leaf blight (Stemphylium vesicarium) and downy mildew of onion (Peronospora destructor). These are the most commonly occurring foliar diseases of alliums in the Northeast, and many of their disease dynamics are closely linked; if one

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white mold infection green beans

White Mold

Pest: White mold (Sclerotinia sclerotium) Pest/disease lifecycle, most common damage symptoms and crops affected: White mold (Sclerotinia sclerotium) is a widespread disease of over 300 species of plants. It is only a sporadic problem in “normal” and dry growing seasons; however, white mold can be very damaging in wet years and, if it goes unrecognized

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tawny garden slug on potato leaf

Slugs and Snails

Pest: Slugs and Snails Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Land slugs and snails are closely related mollusks, known together as “gastropods,” the primary difference between them being that snails have external spiraling shells. There are over 90 terrestrial gastropods found in Maine. The gray garden slug is most common

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spider mite webbing and leaf damage on cucumber plants

Two-Spotted Spider Mites

Pest: Two-spotted spider mites (Tetryanchus urticae) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Two-spotted spider mites are the most common mite pest of crops in the Northeast. Because they thrive in hot and dry conditions, they are commonly found in greenhouses and high tunnels. Spider mites can feed on many crops

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Mexican bean beetle larvae on bean leaf.

Mexican Bean Beetle

Pest: Mexican bean beetle (Epilachna varivestis) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: If Mexican bean beetles have historically been a problem on your farm or in your garden, you will very likely see them again this year. They may be pests on snap beans, dry beans, soybeans and lima beans.

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ToBRVF leaf

Tomato Brown Rugose Fruit Virus

Pest: Tomato Brown Rugose Fruit Virus (ToBRFV) Disease identification: Tomato brown rugose fruit virus, otherwise referred to as ToBRFV, is a highly virulent and aggressive plant virus that can cause serious infections on tomato and pepper species. ToBRFV behaves very similarly to other tobamoviruses such as ToMV (tomato mosaic virus) and TMV (tobacco mosaic virus).

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Puncture damage from ALM

Allium Leafminer

Pest: Allium Leafminer (Phytomyza gymnostoma) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Allium, or onion, leafminer (ALM) is an invasive pest of alliums. Adult allium leafminers are small (approximately 3 millimeters) gray/black flies with a distinctive orange/yellow spot on the tops of their heads, and yellow “knees” (Fig. 1). ALM have

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yellowish discoloration on garlic clove

Waxy Breakdown of Garlic

Condition: Waxy Breakdown (an abiotic disorder) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Waxy breakdown of garlic is a physiological condition that sometimes affects garlic, though typically only rarely in Maine. Development of the condition is not fully understood but often associated with very high temperatures and/or sunscald damage around harvest

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fine white mildew on green leaf

Powdery Mildew of Cucurbits

Disease: Powdery Mildew of Cucurbits (Podosphaera xanthii and Erysiphe cichoracearum) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Management options: Powdery mildew is a common disease of pumpkins and winter squash. All cucurbits are susceptible, but many common cucumber and melon varieties have had powdery mildew resistance bred into them. The disease

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large green tobacco hornworm on tomato foliage

Hornworms

Pest: Hornworms (Manduca sexta, M. quinquemaculata) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Hornworms are probably the most destructive insect that attacks tomatoes. They are giant caterpillars that grow rapidly and can do a vast amount of eating in a very short amount of time. Sometimes it seems that healthy-looking tomato

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asiatic garden beetle on soil surface

Scarab beetles

Pest: Scarab beetles (Asiatic Garden, Japanese, Oriental, Chafers) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: There are several species of scarab beetles that are common in New England turf, fruit and vegetable crops. These were all introduced to the United States. Japanese beetles are the most common and widely distributed. Below

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basil downy mildew on upper surface of leaf

Basil Downy Mildew

Pest: Basil Downy Mildew (Peronospora belbahrii) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Downy mildew of basil was first reported in Uganda back in 1930. Relatively recently it spread to Italy in 2004, France in 2005, United States (Florida) in 2007 and by 2009 had made its way to New England.

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Clavate Tortoise Beetle Adult

Tortoise Beetle

Pest: Tortoise beetle (species in the Cassidinae subfamily) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: These beetles are typically only a very minor pest. They do not typically cause serious damage and do not warrant spraying. The numbers are usually small and the beetles can be picked off by hand, and

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blossom end rot on green tomato

Blossom End Rot

Blossom End Rot Blossom end rot is a familiar sight for many tomato growers, but it can affect other crops as well, such as peppers and squash. Though it may look like a disease, and it sometimes allows infection by secondary decay organisms, blossom end rot is an abiotic growth disorder caused by stressful growing

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early blight on potato foliage

Early Blight

Disease: Early blight on tomato (Alternaria) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Early blight is a serious problem in tomatoes and potatoes, but rarely affects peppers and eggplants. In most years, it is very common; much more common than late blight, which is usually rare in Maine. All aboveground portions

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garlic anthracnose on scape

Garlic Anthracnose

Pest: Anthracnose (Colletotrichum fioriniae) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: The fungus pathogen that is responsible for anthracnose on garlic scapes (Colletotrichum fioriniae), is the same fungus that causes celery anthracnose — described in this pest report from 2019. One theory for the relatively recent appearance of the disease is

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Cutworms

Pest: Cutworms (many species) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Cutworms are occasional pests of many crops early in the season, including carrots, peas, onions, spinach, broccoli and the list goes on and on. Some years they result in major losses, other years result in no loss at all. They

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cucurbit downy mildew lesions on underside of leaf

Cucurbit Downy Mildew

Pest: Cucurbit downy mildew (Pseudoperonospora cubensis) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Cucurbit downy mildew can be very destructive of cucumbers, squash, pumpkins and melons, if conditions are favorable to it. This disease does not overwinter here, and its severity in any given season is often dependent upon when it

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squash bug adult and eggs

Squash Bug

Pest: Squash Bug (Anasa tristis) Pest identification and lifecycle, most common symptoms and crops affected: Squash bugs are serious pests of pumpkins and squash throughout North America. Plant damage, and bug survival, are low on watermelon, very low on cucumber and muskmelon, and highest on squash and pumpkin. Both adults and nymphs feed by inserting

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Squash vine borer

Squash Vine Borer

Pest: Squash vine borer (Melittia cucurbitae) Pest identification and lifecycle, most common symptoms and crops affected: Squash vine borer moths are day-flying moths with a 1 to 1.5 inch wingspan and bright orange-red markings. In flight, they look like wasps. There is thought to be only one generation per year in New England with adults

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tarnished plant bug

Tarnished Plant Bug and Four-Lined Plant Bug

Pests: Tarnished Plant Bug (Lygus lineolaris) and Four-Lined Plant Bug (Poecilocapsus lineatus) Pest identification and lifecycle, most common symptoms and crops affected: The tarnished plant bug is a small (6 mm), bronze, brown and black bug that feeds on a very wide variety of plants (up to 300 different species). They overwinter as adults under

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"hopperburn" damage

Potato Leafhoppers

Pest: Potato Leafhoppers (Empoasca fabae) Pest identification and lifecycle, most common symptoms and crops affected: The potato leafhopper has been arriving here in New England earlier and earlier. If you see unexplained yellowing of leaves of beans or potatoes, check for the critter. They primarily feed on beans, potatoes, eggplants, strawberries and alfalfa, but will

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cucumber beetles on yellow blossom

Striped Cucumber Beetle

Pest: Striped cucumber beetle (Acalymma vittatum) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Striped cucumber beetle is our most serious early-season pest in cucurbit crops. These beetles spend the winter in plant debris in field edges and with the onset of warm days and emergence of cucurbit crops they rapidly move

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Colorado Potato Beetle

Pest: Colorado Potato Beetle (Leptinotarsa decemlineata) Pest identification and lifecycle, most common symptoms and crops affected: As with most other insects and plants, there is a direct relationship between higher temperatures (in the range between about 55 and 90 degrees) and faster rate of development. That includes egg-laying, egg hatch, larval growth and feeding rates.

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Seedcorn Maggot and Other Maggots

Pests: Seedcorn maggot (Hylemya platura), Onion maggot (Delia antiqua), Cabbage maggot (Delia radicum) Pest identification and lifecycle, most common symptoms and crops affected: Seedcorn maggot larvae feed on seeds and young seedlings of many crops (including corn, beans, beets, peas, spinach, onions and Brassicas). The first symptoms are usually poor germination (or failure of seedlings

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Seedling Problems

In the early spring, when most plants are still in greenhouses — a much more controlled setting than gardens and fields — a lot of the problems that arise are abiotic (i.e., not infectious). Sometimes abiotic issues are transient (e.g., cold temperatures) so it’s good to both check new growth to see how it looks

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Leek moth adults

Leek Moth

Pests: Leek Moth (Acrolepiopsis assectella) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: Leek moth is a newer invasive pest of allium crops like onions, garlic, shallots and chives, and, as the name suggests, they are particularly fond of leeks. As with most moth pests the crop damage is from its larval

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Three-lined potato beetle adults

Three-Lined Potato Beetle

Pests: Three-Lined Potato Beetle (Lema daturaphila) Pest/disease identification and lifecycle, most common damage symptoms and crops affected: The favorite foods of the three-lined potato beetle are crop and weed species in the Physalis genus, notably tomatillo and husk cherries. Potatoes, tomatoes and eggplants are also sometimes attacked. The adult of this pest is about the

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Spinach leafminer eggs on left. Larvae at middle and mining damage right.

Spinach Leafminer and Beet Leafminer

Pests: Spinach leafminer (Pegomya hyoscyami), Beet leafminer (Pegomya betae) Pest/disease identification and lifecycle, most common symptoms and crops affected: These closely related species of leafminer attack spinach, beet, chard and some weeds, such as lambsquarters. The adult is a fly that lays its eggs on the undersides of leaves. Eggs hatch in as few as

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Imported cabbageworm and feeding damage

Cabbageworm

Pests: Imported Cabbageworm (Pieris rapae), Diamondback Moth (Platella zylostella), Cabbage Looper (Trichoplusia ni) The first sign of imported cabbageworm is typically one or more white moths with dark marks on their wings fluttering around brassica plants during the day. Also known as cabbage whites, these moths lay ⅛-inch long eggs singly on brassica crop leaves,

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Damage to onion leaves caused by thrips

Onion Thrips

Pest: Onion Thrips (Thrips tabaci) Pest/disease Identification and lifecycle, most common symptoms and crops affected: Onion thrips are active already, and if they have been a problem for you in years past it is time to start scouting for them. They are very tiny and easily overlooked until the onion plants start showing leaves that

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Garden Springtails

Pest: Garden Springtails (Collembolla) Pest/disease identification and lifecycle, most common symptoms and crops affected: Springtails are a very diverse group of soil dwelling arthropods, that largely feed on decaying organic matter. As such, most springtail species are playing a beneficial role in a healthy soil’s food web. That knowledge may be of little relief, however,

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Sunscald/Windwhip

Pest/disease identification and lifecycle, most common symptoms and crops affected: Plants that have not yet been hardened off thoroughly, or can’t get all the water they need, can suffer from something akin to a sunburn. The damage usually shows up first as a bleaching of exposed leaf surfaces, typically higher up on the plant, though

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Flea Beetles

Pests: Crucifer Flea Beetle (Phyllotreta cruciferae) and Striped Flea Beetle (Phyllotreta striolata) Pest/disease identification and lifecycle, most common symptoms and crops affected: Crucifer and striped flea beetles feed on brassica crops as well as weeds that are in the same family, such as yellow rocket or wild mustard. Larvae feed on the roots and flea

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Asparagus Beetle

Pest: Asparagus Beetle, Common (Crioceris asparigi) and Spotted (Crioceris duodecimpunctata) Pest identification and lifecycle, most common symptoms and crops affected: Common Asparagus Beetle (Crioceris asparigi) Blue-black, shiny, smooth and about 6 to 9 millimeters (1/4 inch) long, with three large yellow, squarish spots with red margins along each wing cover. Eggs are black, laid standing on

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Edema

Pest: Edema Pest/disease identification and lifecycle, most common symptoms and crops affected: Edema usually shows up on tomato seedlings when they have been waiting through lots of cloudy cold days. It is also a common problem in plants in the cabbage family, and some house plants. Blisters or bumps appear on the surface of the

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Floating Row Cover Foils Potato Pests

By Jonathan Mitschele In late July 2017 I discovered that my potato plants were not doing well. Leaves were yellowing and the plants were not growing as expected. Suspecting some sort of blight, I sent photos to Eric Sideman at MOFGA. He thought the problem was potato leafhoppers and referred me to a MOFGA pest

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Dealing with Pest Animals in the Organic Garden

By Will Bonsall Note: Certified organic producers should check with their certifier before using any pesticides (including pest repellents) not mentioned on their organic farm plan. When using pesticides on crops grown commercially and intended for human consumption, an applicator’s license may be required. See https://www.maine.gov/dacf/php/pesticides/applicators/licensing.html. One of the main problems with growing the foods we

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A Frustrating New Brassica Pest The Swede Midge

Swede midge larvae, circled Broccoli leaves contorted by swede midge larvae feeding Swede midge damage in broccoli Multiple heads of Veronica cauliflower – a result of swede midge feeding By Caleb Goossen, Ph.D. Photos by David Fuller Over the coming years, farmers and home gardeners in Maine will likely encounter damage on their brassica plants

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Tend to browntail moth webs now

  Browntail moths. English photo March 1, 2020 If you find browntail moth webs within reach, clip them by mid-April and destroy the webs by soaking them in soapy water or burning them. Winter is the best time to clip webs due to the low risk of exposure to the caterpillars’ toxic hairs, due to caterpillar dormancy,

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Animal Pests in the Garden

  Without a contiguous perimeter of metal deer fencing that is at least 8 feet tall, these animals are likely to enjoy your crops.   Anyone can set a live trap anytime and relocate woodchucks, raccoons or skunks. By Caleb Goossen, Ph.D. The three most common mammal pests that gardeners ask me about are deer,

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Another Maine Area Affected by Leek Moth

Leek moth cocoon Adult leek moths A leek plant destroyed by leek moth larvae. By David Fuller Photos by the author Leek moth was identified in 2017 by Cooperative Extension in Jackman. Those populations have subsequently migrated south to Long Pond Township, a distance of about 10 miles. Now leek moth has also been found in Rangeley

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Controlling Pest Insects in the Organic Garden

One way to manage pest insects is to create habitat in your garden for beneficial insects such as ladybugs. Oxalic acid in the leaf blades (not petioles) of rhubarb can help repel flea beetles. Row cover, although a synthetic material, can last several years with care. An infusion of tansy, growing here with goldenrod, may

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Managing Cabbage Aphids

Cabbage aphids on kale growing in a tunnel. Photo by Eric Sideman Habitat plants flowering among brussels sprouts. Photo by Becky Sideman By Eric Sideman, Ph.D. Although it may seem so, the cabbage aphid is not a new pest. My favorite discussion of this pest is in a 1928 text called “Destructive and Useful Insects, Their Habits and

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Leek Moth

Leek moth. Photo by David Fuller Leek moth larvae on the inside of an onion leaf. Photo by David Fuller By Dave Fuller, Agriculture and Non-Timber Forest Products Professional, UMaine Cooperative Extension, Franklin County Leek moth (Acrolepiopsis assectella Zeller), a very destructive pest of all of the Allium genus, was first found in Jackman, Maine,

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Next Years Pest Management Begins Now

Seedcorn maggots feeding on young spinach. Seedcorn maggots in soil amended with soy meal. European corn borer overwintering in a corn stalk. Early blight on lower leaves of tomatoes. Close-up of early blight on tomato. Late blight on potato. By Eric Sideman, Ph.D. Fall garden care is the beginning of spring  garden pest management. Many

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Beneficial Insects

Cocoons of a wasp that parasitized a tomato hornworm. Eric Sideman photo Beneficial insects are part of complicated relationships in ecosystems, and we are just beginning to understand those relationships, said Kathy Murray, Ph.D., an entomologist and Integrated Pest Management (IPM) program coordinator with the Maine Department of Agriculture, Conservation and Forestry. Murray is also

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Row Covers

By Kerstin Tengeler I am an organic vegetable farmer in St. Lawrence County in upstate New York. My partners and I use row covers on our 4-acre farm to extend our growing season and to protect our crops from insects and deer. Because minimizing the use of plastics that end up in landfills is important

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Leafhoppers Again?

These apple leafhopper nymphs and adult show the shape of the insect.  Potato leafhoppers are the same shape but greenish in color. Photo courtesy of Don Barry, Univ. of Maine Pest Management Office. By Eric Sideman, Ph.D. MOFGA’s Director of Technical Services Last year towards the end of June and early July, I started to

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Drosophila

Figure 1 – The female spotted wing Drosophila (fruit fly), a new pest in New England, uses her serrated ovipositor to make a hole in sound fruit and lay her eggs, which develop into larvae in the fruit. Photo courtesy of Alan Eaton of the University of N.H. By Eric Sideman, Ph.D. I am usually

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Potato Beetle

By Eric Sideman, Ph.D. Director of Technical Services, MOFGA I can understand farmers who tell me they’re tired of hearing about the new USDA Rule and the regulation of organic vegetable production. I have said many times that the new rule is really 99% similar to MOFGA’s old standards, and I still claim that. Then

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Pest Control

A Natural System Just Dying for Balance By Jean English Michael Zuck gave an inspiring talk at MOFGA and Cooperative Extension’s Farmer to Farmer Conference about using teosinte and other plants as “banker plants” in greenhouses – plants that support pests that, in turn, support beneficial insects. English photo. Michael Zuck’s fascination with nature’s multiple

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Sideman Summer 09

By Eric Sideman, Ph.D. Does summertime bode many afternoon hours in the hammock thinking about what’s good in the garden to go with that hamburger hot off the grill – or hours of worrying what could go wrong in that garden, which looks so good this early in the season? Balancing fun with fret is

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Pesticide Regs

The OMRI categories that may include pesticides are: amino acids Bacillus thuringiensis Beauveria bassiana biological controls boric acid botanical pesticides calcium polysulfide copper products corn gluten diatomaceous earth enzymes nonsynthetic fungicides gibberellic acid nonsynthetic herbicides hydrogen peroxide inoculants lime sulfur limonene neem cake and extract nonsynthetic nematicides narrow range oils nonsynthetic oils pheromones potassium bicarbonate

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Helping Plants

Toki Oshima illustration. By Jan Suszkiw, Agricultural Research Service Information Staff People aren’t the only ones to benefit from salicylic acid, the active ingredient in aspirin. Spraying this naturally occurring compound onto some plants triggers natural defenses that keep harmful fungi, bacteria and viruses at bay. Plants have always had some means to defend themselves,

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Garlic Oil

An oil made from garlic can be mixed with a percentage of bird seed and fed to starlings in areas that you want them to avoid. After a taste of the garlic oil-impregnated seed, they’ll do just that. Photograph from Corel Corporation, used with permission. by John K. Borchardt Garlic repels more than just vampires.

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Pests

Squash bug. Photo credit: 1 By Eric Sideman, Ph.D. Fall chores are my favorites. At no other time do I have more hope for a successful garden than the fall before. Autumn is even better than spring, especially last spring when we all realized very early in April that it was not going to be

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Carrot Rust Fly

The larva of the carrot rust fly is a maggot that tunnels into carrots.  Photos by Eric Sideman. by Eric Sideman, Ph.D. I have lived in the same house in Greene, Maine, for over 20 years, and the carrot rust fly has been a problem only one of those years. But it was awful that

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