Nematoda, Tylenchida, Tylenchidae .
Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plants: distributed throughout Europe, this nematode species may attack more than 1,200 species of wild and cultivated plants. There are about 20 morphologically similar biological forms, each having a specific host-range.
Affected crops include mainly Gramineae (oats, rye, maize), Liliaceae (onion, garlic, leek), Leguminosae (lucerne, bean, pea, clover), Solanaceae (potato, tobacco), Cruciferae (cabbage, turnip, mustard), Moraceae (hemp, hop), etc.;.
- Taking advantage of the humidity resulting from rain or dew, juveniles and adults leave the soil and, covered by a film of water, travel along the surface of stems and leaves.
They penetrate the base of stems or the bulb scales and form cavities by dissociating cells. This leads to the formation of reddish-brown lesions that may be relatively large.
Towards the end of the growth period, these dried lesions contain a downy substance ('nematode wool') made up of millions of individuals in a state of diapause (slowed life), thus constituting a potential of infestation for following crops.
- Individuals feed on cell juices which they suck up with their stylet after injecting saliva into the cells. Toxic substances contained in the saliva produce necroses and distortion of the tissues.
- This nematode species can also infest seeds and dissemination may occurs during sowing (lucerne).
- Ditylenchus dipsaci can survive in the soil in a state of diapause for 8-9 years. Each stage overwinters in the stems, petioles and bulbs of cultivated plants or weeds. Reproduction occurs throughout the year, except in cold weather.
- Primary infestation of beet and carrot starts after germination, leaves becoming distorted. In autumn, the collar becomes spongy, pulverulent and comes off the root.
- Leaves of oats, rye or lucerne become distorted, stems thicken, tillering is excessive and the plant is short and stunted (*) .
- Early and heavy attacks may lead to the disappearance of young plants (*) .
- Stems of maize are shortened, swollen and necrosed. Coronary roots disappear, which leads to a lodging of crops (*) .
- barley and wheat are rarely attacked.
- The base of young onion, leek, garlic and shallot plants becomes swollen and leaves distorted. Bulbs later become blistered and cracked (*) .
- pea and bean plants remain short, get shrubby and many of them die.
- potato plants become distorted, the stems and tubers undergo necrosis.
- Young tobacco plants dry out and die. Older plants lodge.
- Leaves of strawberry are small and distorted, petioles are short, thick and twisted. The foliage dries out and falls off.
In addition to the direct damage caused by nematodes, affected tissues are generally infected by various micro-organisms which cause them to rot.
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