Contributors to this page: ICARDA, Aleppo, Syria (Siham Asaad, Abdulrahman Moukahal).
Stem and bulb nematode, stem and bulb eelworm
Ditylenchus dipsaci(Kühn, 1857) Filipjev, 1936
Other scientific name
Tylenchus dipsaci (Kühn) Bastian
D. dipsaci is one of the most devastating plant parasitic nematodes, especially in temperate regions. Without control, it can cause complete failure of host crops.
D. dipsaci causes swelling and deformation of stem tissue or lesions which turn reddish-brown then black, depending on cultivar and environmental factors. Newly formed pods take on a dark-brown appearance. The lesions envelop the stem and increase in length, often advancing to the edge of an internode. Leaf and petiole necrosis is also common under heavy infestations, but can be confused with symptoms induced by fungal leaf pathogens. Infected seeds are darker, distorted, and smaller in size and may have speckle-like spots on the surface. Heavy infestations often kill the main shoots, stimulating secondary tiller formation. The more severe symptoms are usually induced by the “giant race” on legumes.
D. dipsaci is known to attack over 450 different plant species, including many weeds. However, it occurs in more than ten biological “races” some of which have a limited host-range.
D. dipsaci occurs locally in most temperate areas of the world
Biology and transmission
In international trade D. dipsaci is liable to be carried on dry seeds and planting material of host plants. In the field the fourth-stage juvenile can withstand desiccation for many years, and although soil densities seem to decrease rapidly, the nematode can survive for years without a host plant. Nematode survival and damage are greater in heavy soils as compared to sandy soils. It can also survive on a number of weeds. Irrigation water and cultivation by contaminated farm tools and machinery are other sources of inoculum disseminate.
Detection/indexing method in place at the CGIAR Center at ICARDA
- Not significantly important
- Nematode-free (certified) seeds and planting material are most essential to prevent crop damage by D. dipsaci. Hot-water treatments with different temperature-time combinations, depending on type and state of seed material, are operational and efficient to control D. dipsaci. The use of tolerant or resistant cultivars can also reduce the damage.
Procedure followed at the center in case of positive test
- Fumigation, destroying seed
References and further reading