PESTS OF WHEAT :: Major Pests :: Wheat-gall Nematode

7. Wheat-gall Nematode: Anguina tritici (Tylenchidae: Tylenchida) 

Distribution and status: Cosmoplitan. It causes ear-cockle or mamni disease. The nematode is also the carrier of the bacterial yellow slime ear-rot (tundu disease) caused by Corynebacterium tritici

Host range: Rye, spelt and emer. Oats and barley are immune.

Damage symptoms: If the black rounded mamni galls are soaked in water overnight, the coat softens and a large number of larvae are set free.Affected plants are more or less stunted and their leaves are wrinkled, rolled or twisted. A variable number of grains in an infested ear may produce galls. The diseased ears are shorter and thicker than the healthy ones and the glumes are spread farther apart

Bionomics: Under natural conditions, the dry galls either fall to the ground from the ripe ears or they are harvested and find their way to the stores along with the healthy produce. The galls though dry remain viable for long periods. Single gall contains 800 to 30,000 larvae which revive and become active when the gall is moistened.
     
When wheat is sown, the galls become soft on imbibing moisture and the larvae are set free into the soil. From there, they reach the host plants, if available within a distance of one third of a metre. They rise up the plant and find a site for feeding as free parasites on the young leaves and the growing-points. Later on, as the plants approach the earing stage, they penetrate into the primordia of the flower-buds and form the galls instead of normal seed.
     
In the developing galls, the larvae mature into males and females, as the case may be. A single gall at this stage may contain 40 females and an equal number of males. They mate within the gall and the gravid females lay a large number of eggs. The young larvae on emerging from the eggs develop up to the second stage and then become dormant. They remain in that state in the dry galls till the next sowing season. There is only one generation in a year.

Management: The wheat gall nematode can be controlled by separating the galls from the wheat seed by floating them on water in a tub. The galls, being lighter, float on the surface and may be skimmed off. The seed should then be dried before sowing. (ii)The pest can also be suppressed by sowing clean seed in uninfested soil. Only one year's fallowing is sufficient to eradicate this nematode from the fields.