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Pests & Diseases
Allium or onion leafminers can quickly infest plants, causing leaves to become curled and deformed. Adults are small black or gray flies with a characteristic orange spot and lay eggs at the base of plants.

Once hatched, the small larvae pierce leaves and create channels through the leek, which can allow bacteria and pathogens to enter the plants.

Onion thrips are small insects varying in color from yellow to black. The adults lay eggs on leeks and other onion plants. Once hatched, larvae feed on leaves then move into soil to pupate. Infestations can result in stunted growth, twisted leaves, smaller bulbs, reduced yields, and plant death.

Onion maggots are a major threat to leeks, shallots, onions, garlic, and chives. The pests burrow underground to feed on bulbs, dig tunnels, destroy tissue, and leave plants vulnerable to a host of diseases.

White rot can live in soil for years and infect plants. Leaves turn yellow, wither, and overall growth is stunted. In some cases, a fuzzy coating forms on the bulb and sheaf, making the leeks unmarketable.

Downy mildew typically forms on plants due to overly wet and cool temperatures, leading to the formation of long, light-colored blotches and velvety purple spores on leaves. It also causes the sheaf to soften and may lead to premature sprouting of leaves.

Basal rot is a common disease of leeks, onions, and garlic, particularly in transplants. The soilborne fungus causes leaves to turn yellow and die. Roots will turn dark brown or pink, and a white fungus may appear on the bulb.

Other diseases of concern include botrytis leaf spot and neck rot, pink root, purple blotch, rust, smudge, and white tip.

Storage & Packaging
Once harvested, leeks should be washed and stored in a moist, cool environment with temperatures between 32 and 40°F. Wilting will occur if proper moisture levels (95 to 100% relative humidity) are no maintained. Leeks are sensitive to ethylene exposure.

Leeks are typically bunched and packed upright in boxes or containers. When trimmed and packed in sealed polyethylene bags and stored in ice, they can last for up to 10 weeks. When stored in a controlled atmosphere at 32°F, leeks may last up to several months.

References: Clemson University Extension, Michigan State University Extension, New England Vegetable Management Guide, Ontario Ministry of Agriculture, University of California, University of Maryland Extension, University of Wisconsin Extension.


There is no U.S. grade information specific to leeks at this time.

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