Common Garlic pests

Onion thrips (Thrips tabaci) are the most common insect pest of garlic. They are tiny, slender, straw-colored insects that rasp the leaves and cause silvery streaking, stippling, and curled or distorted foliage, usually worst in hot, dry weather. Onion maggot (Delia antiqua) is the larva of a small fly that tunnels into the base and bulb, causing wilting, yellowing plants and rotted, maggot-riddled bulbs. Allium leafminer (Phytomyza gymnostoma), an invasive pest spreading in the Northeast and Mid-Atlantic, leaves rows of white oviposition dots near leaf tips and mines that lead into the bulb. Bulb mites (Rhizoglyphus species) are tiny, slow-moving pests that feed on cloves in the soil and in storage, and deer or rabbits generally leave garlic alone because of its strong odor.

Common diseases

White rot (Sclerotium cepivorum) is the most serious garlic disease. It causes yellowing, wilting foliage, a fluffy white fungal growth at the base, and tiny black poppy-seed-sized sclerotia that persist in the soil for many years. Basal rot (Fusarium) produces yellowing leaves and a soft, brown decay of the basal plate that often continues in storage. Downy mildew (Peronospora destructor) shows as pale, fuzzy purplish-gray patches on leaves in cool, wet conditions, while purple blotch (Alternaria) and botrytis neck rot cause leaf lesions and a soft gray mold that ruins bulbs after harvest. Garlic is also affected by several mosaic and yellow-streak viruses spread by aphids and mites, which cause yellow streaking and stunting and are carried in infected planting stock.

Prevention

Rotate garlic and other alliums (onion, leek, shallot, chive) so they do not return to the same bed for at least three to four years, which starves soilborne fungi and reduces maggot and mite pressure. Plant certified disease-free cloves or clean, firm bulbs saved from healthy plants, and avoid replanting stock from any bed that showed rot. Give plants full sun, good spacing, and airflow, keep beds weed-free, and water at the base in the morning so foliage dries quickly. Choose well-drained soil, plant at the right time for your region (usually fall in most of the US), and remove and discard crop debris and cull bulbs at the end of the season.

Organic control

Cover new plantings with lightweight floating row cover from emergence to exclude onion maggot flies and allium leafminer during their egg-laying flights, sealing the edges well. For thrips, hose plants with a strong stream of water and encourage natural enemies such as minute pirate bugs, lacewings, and predatory mites; where thrips are heavy, insecticidal soap or a neem-based product applied to run into the leaf axils can help, and repeat applications following the product label are usually needed. Yellow or blue sticky traps help detect and reduce adult leafminers and thrips. Remove and destroy any plants with white rot or basal rot promptly, and cure harvested bulbs thoroughly in a warm, dry, airy spot to prevent botrytis neck rot; always read and follow the label on any product you use.

Scouting & monitoring

Scout weekly once growth is active, focusing on the leaf bases and inner leaves where thrips hide and where you will see their silvery stippling. In spring, watch for the white egg-laying dots of allium leafminer along the upper leaves and for wilting, off-color plants that signal onion maggot or basal rot below ground. Check for pale fuzzy patches after cool, wet spells, which point to downy mildew, and pull a few plants late in the season to inspect the basal plate for firmness. At and after harvest, inspect and sort bulbs, culling any that are soft, moldy, or show the black sclerotia of white rot before they go into storage.

Tips

Your best defenses are long allium rotation and clean planting stock, since the worst garlic diseases live in the soil or travel inside infected cloves. Cure and store bulbs well, and never replant cloves from a bed that showed rot or from bulbs that were soft at harvest.

General home-garden IPM guidance, focused on prevention and least-toxic control. Always read and follow the product label for any pesticide, including organic products. Page updated Aug 4, 2026.