Category Archives: Onion Diseases

Credits:Biovision-Infonet

Fusarium oxysporium f.sp. cepae) Credits: Biovision-Infonet The above ground symptoms constitute yellowing of leaf blades at the tip. The yellowing at later stages covers the whole blade. The affected leaves shrivel and decay. Diseased plants can be easily pulled out because the root system is rotted. Affected roots are dark brown, flattened, hollow and transparent. […]

(Puccinia porri) Credits: Biovision-Infonet Affected leaves show small reddish to dusty orange spots (pustules). These later turn black and are covered until maturity by leaf epidermis. Leaves that are heavily infected turn yellow and die prematurely. A new crop of leaves may develop and the bulb size is usually reduced. The fungus attacks also leek, […]

(Sclerotium cepivorum) Credits: Biovision-Infonet The disease occurs mainly in the field and seldom causes injury in storage. The disease is called white rot because of characteristic basal bulb rot where the tissue is covered with white mat of fungal growth. Later numerous rounded black fungal bodies (sclerotia), each about the size of a pin’s head, […]

(Colletotrichum circinans) Credits: Biovision-Infonet It usually appears in fields just before harvest and continues to develop during storage period. Under warm and wet soil conditions, it can cause seedling damping-off. The most common symptom is the small dark green or black stains (dots) on outer scales of bulbs. The dots develop concentric rings. In severe […]

(Pseudomonas cepacia) Credits: Biovision-Infonet In contrast to soft rot and slippery skin, infected scales are not water-soaked but are slimy and yellow. Symptoms usually visible only after onions are dug. The upper portion of the bulb shrinks, and in advanced stages of the disease, the outer dry skin readily slips off during handling while the […]

(Pseudomonas allicolai pv. allicola) Credits: Biovision-Infonet There are no symptoms on the outer surface of bulbs during early stages of disease development. When the bulb is cut open lengthwise, one or more of the inner scales can be found water-soaked or appears as if it has been cooked. The rot does not progress crosswise in […]

(Erwinia carotovora subsp. carotovora) Credits: Biovision-Infonet This is a big cause of loss in storage onions. Bacteria Erwinia carotovora subsp. carotovora) can enter the neck tissue as plants mature and then invade one or more scales. At this stage, the affected tissues are water-soaked and pale yellow to light brown. As the rot progresses, the […]

(Alternaria porri) Credits: Biovision-Infonet Purple blotch attacks onion, garlic, leek and other Allium crops. Initially, small white sunken spots develop on the leaves. These enlarge and under moist conditions, turn purple with a yellowish border and are often covered with a sooty deposit of spores. After 3-4 weeks the leaves turn yellow and collapse. Bulbs […]