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

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

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

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

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.

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).

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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,

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

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,

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

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

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

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