Why’s there a yellowish powder on my garlic plants?

Credit: graibeard

Q: My garlic plants are all suddenly producing flowering stalks. There is also a powdery-orange material on the leaves.

What might be causing this?

“Rust” (Puccinia allii) is a fungus that is often seen on garlic plants, as well as onions, leeks, shallots and wild Allium spp. The yellow-orange powder is actually composed of many spores. The spores are released from pustules on the stem. They will later turn black.

“Rust” fungi tend to overwinter on garlic and other related Allium spp. The fungi usually cause little or no damage to garlic. But, in cases where the fungi do eat away at the foliage, such as with green onion or chives, a spray routine may be required. You can also try crop rotation – plant or grow non-onion family members with your garlic for at least a year. Remove all volunteer onions or garlic, provide good air-circulation, avoid overhead watering, and avoid handling plants when they are wet.

“Bolting” is a physiological phenomenon that occurs when the temperature fluctuates from cool to warm, and back to cool again. The plant behaves as if it has overwintered, and its reproductive cycle is triggered. The plant sets flowers as a means of reproducing. Due to unusual weather patterns this year, bolting is unavoidable. Bolting causes garlic to eventually produce smaller bulbs.