Yellow Leaves in Garlic

Types

• The garlic plant, Allium sativum, is susceptible to several different diseases that can result in yellow leaves. Basal rot, white rot, downy mildew, botrytis rot and penicillium decay are common afflictions of this woody, perennial herb. The majority of these hide in the earth, so yearly rotation of crop space is crucial in helping the garlic plant avoid these problems.

Basal Rot

• A yellowing and eventual dieback of the leaves is a symptom of basal rot. This slow-to-develop disease also brings about a white fungal growth at the base of the garlic bulb, a dilemma that can result in a rotting of the garlic bulb both before and after harvesting. This disease typically appears when the temperature is high and the plant is already stressed by other diseases or insects.

White Rot

• Signs of white rot are nearly identical to those of basal rot, reports the Cornell University Plant Disease Diagnostic Clinic. Yellow leaves in garlic and a dieback of those leaves is the primary symptom. The difference is that white rot occurs much more quickly than basal rot, and death of the garlic plant is more rapid. This fungus prefers cool temperatures under 75 degrees Fahrenheit and attacks plants in the spring.

Downy Mildew

• Downy mildew appears as a white, furry discoloration amid the leaves of the garlic plant, accompanied by a yellow discoloration. The growth of older plants can be stunted, and the disease is typically fatal to younger plants. Bulbs that have been harvested and are experiencing the disease will show a blackened neck and shriveled body. Spores of this disease are spread by the wind and standing water.

Penicillium Decay

• Penicillium decay brings about a yellowing of the garlic plant and reduced growth. The fungus can appear on the cloves as a blue and green mass. Once any of these diseases are established in soil, it is important to rotate away from growing garlic, onions, leeks or any members of this family for several years. Insects known as nematodes also cause yellowing, deformed garlic bulbs.

Botrytis Neck Rot

• Botrytis neck rot causes the outer leaves of the garlic plant to yellow and die; in extreme cases, the affliction may be fatal for the entire plant. The neck will appear water-logged at the soil line and a black fungus will appear on the stem. This disease is prevalent in cool, wet weather and similar soil.