Garlic Diseases

Not too many pests bother garlic, but don’t plant it where you have had trouble with wireworms or nematodes. Disease is more of an issue in poorly drained soils.

Downy mildew: Pale spots or elongated patches on leaves; gray-purple fuzzy growth on leaf surface; leaves turning pale then yellow; leaf tips collapsing

Comments

Disease emergence favored by cool temperatures and leaf wetness

Management

Avoid planting infected sets; rotate crops to non-allium species for 3-4 years; plant in well-draining areas and do not overcrowd plants; destroy all infected crop debris; apply appropriate foliar fungicides taking care to apply thoroughly to waxy leaves

Purple blotch: Small water-soaked lesions lesions on leaves or stalk with white centers; which enlarge to become zonate and brown to purple in color with red or purple margin surrounded by yellow zone; large lesions may coalesce and girdle leaf, killing any tissue between the lesions and the leaf tip; severely infected foliage may die

Comments

Disease emergence favored by wet foliage, with sporulation occuring during the night during periods of high humidity

Management

Cultural controls include long rotations with non-hosts and the reduction of leaf wetness by planting in well-draining soil and timing irrigation to allow plants to dry adequately during the day; some fungicides are effective at controlling the disease but should be rotated for optimal control

RUST: Small white flecks on leaves and stems which develop into circular or elongated orange pustules; severe infestations can cause leaves to yellow and die

Comments

Favors high humidity but low rainfall; spores can be transported over long distances by wind

Management

No resistance known; use only disease-free seed and plant in well-draining soil; control weeds around crop; apply appropriate protective fungicide.

White rot: Older leaves yellowing; stunted growth; death of all leaves; fluffy white growth on base of bulb which spreads up bulb to storage leaves

Comments

Once disease is established the field is unusable for garlic production; fungus can survive in soil for 20 years and is one of the most damaging diseases of Allium crops worldwide, causing major crop losses

Management

Fungicide treatment may not be effective at controlling white rot under conditions which are favorable to the fungi's development and control may have to rely on cultural methods: avoid transferring soil or plant material between sites; treat seeds with hot water prior to planting; use a long term rotation with non-allium crops; apply appropriate fungicides if available

Mosaic Garlic mosaic: Mosaic patterns on leaves; chlorotic mottling or streaks on leaves; stunted plant growth and reduced bulb size

Comments

Transmitted by aphids; infections can be latent and produce no symptoms; infection in garlic are often found alongside other viruses such as onion yellow dwarf

Management

Plant virus-free cloves that were produced from meristem tip culture in virus-free conditions

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