Stubby-root nematode symptoms and their cultural management in Onion

Causal Agent: Paratrichodorus allius

Symptoms:

• Plants are stunted, turn yellow or may be killed when infection occurs at the seedling stage.
• Infected root systems develop numerous stubby branches, often in clusters, as a result of nematodes feeding on root tips.
• Distinctive lesions are not visible; however, discoloration and necrosis will occur on infected roots due to secondary infections by other organisms.
• The stubby-root nematode is a strictly external feeder and therefore will not be embedded in root tissue like the rootknot nematode.

Control:

• Treatment of infested soil with fumigants and nematicides reduces nematode populations.
• Flooding followed by soil drying can also decrease the population density.
• Long term rotation to resistant crops may give some control.