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Onion: Stem and bulb nematode symptoms and their cultural management

Stem and bulb nematode symptoms and their cultural management in Onion

Causal Agent: Ditylenchus dipsaci


  • Infected young seedlings are stunted, pale and have swollen areas along the cotyledons.
  • Leaves can develop yellowish-brown spots, can be short and thickened and stem swelling (bloating) can occur.
  • As the disease progresses, the foliage collapses and the stems and necks of bulbs soften.
  • The bulb scales become soft and light gray.
  • Infected bulbs are light in weight, may be malformed or produce sprouts and double bulbs.
  • Fungal and bacterial secondary infections are common and often give off a foul odor.


  • To avoid introducing the nematode, check onion sets to verify they are disease free prior to planting.
  • If the nematode is present in the soil, fumigation can give good control.
  • Complete removal and destruction of cull piles, volunteer onions and host weeds are important for reducing this disease.
  • Also, a four year crop rotation to non-hosts such as spinach, carrots, beets, crucifers, lettuce or grains has proven effective.
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Please note that this is the opinion of the author and is Not Certified by ICAR or any of its authorised agents.