Oulema oryzae

Scientific Name Oulema oryzae (Kuwayama)
Synonyms Lema oryzae
Common Names English: Rice Leaf Beetle; Spanish: mayate de la hoja; German: Ostasiatisches Reishähnchen; French: Leme du riz; Japanese: Ine-dorooimusi
Description The adult beetle is about 6-8 mm long, it has a brown pronotum and black dotted elytra, both appear unusually shiny. The larva is 4-5 mm long, its brown color typically hidden by a cover of its black excreta.

Biology

Damage

Adults and larvae of Oulema oryzae feed on the plant tissue between the leaf veins, leaving mines or scarifications parallel to them that can give the leaf a scorched appearance. Severe infestation will cause the leaves to become chlorotic.

Heavily infested fields can look completely withered and faded instead of green from a distance. Excessive feeding may cause plants to get stunted, reduces the number of tillers and thereby the yield.

Lifecycle

O. oryzae overwinters as an adult under grasses, plant litter or in other sheltered places near to the paddy fields. In spring, the beetles migrate towards the nursery beds, where they start feeding on the leaves. Soon afterwards, the females lay their eggs in small lumps on the leaf blades, normally close to the tips, and cover them with excreta. In contrast to most other insects, the adult beetles are not attracted to light. The larvae hatch after about 5-10 days. They begin to feed on the leaves immediately and pass through four instars in 2-3 weeks.

For pupation the larva spins a white cocoon which is firmly attached to a leaf. The pupal quiescence lasts about 1-2 weeks. The emerging beetles continue to feed for about 3 months on the leaves, and then, in Japan at about the middle of August, migrate to their winter hiding places. Usually there is only one generation of Oulema oryzae per year.

Occurrence

Additional Crop Information

It has a great number of other hosts in the grass family besides rice.

Agricultural Importance

The rice leaf beetle is found in temperate regions of China, Japan, Korea and parts of the former USSR, mostly in highlands and wetland areas. Low infestation causes only moderate damage and yield losses, but, as great population fluctuations are possible, careful observation and, as the case may be, treatment are necessary.

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