|Scientific Name||Nephotettix virescens (Distant, 1908)|
|Synonyms||Nephotettix bipunctatus, N. impicticeps|
|Common Names||English: Green rice leafhopper; German: Grüne Singzikade; French: Cicadelle verte orientale du riz; Japanese: Taiwan tumaguro-yokobai|
The body shape of adult N. virescens is that of a typical leafhopper. It is bright green in color, whereas the nymphs are more yellowish-green.
The first symptoms of infestation are yellow, transparent spots that appear mainly on the tips and along the mid-ribs of the leaves. These are soon followed by grayish-white, and later brown spots on the leaves and leaf sheaths of the young plants. Deposits of honeydew gradually cover the plant surface, creating a basis for the development of sooty molds. The soft, whitish exuviae can often be found adhering to the sticky surface of the leaves.
As a rule, the damage first becomes noticeable around the edges of the paddy field. The insects tend to prefer the peripheral leaves of a plant over the central ones, and are found mainly on the dorsal leaf surface.
Both nymphs and adults feed on leaves, leaf sheaths and young stems. They prefer to suck on the phloem, but sucking on the xylem has been observed on resistant rice varieties. A single female can produce up to 300 eggs: it deposits them in groups of 8-15 in slits under the epidermis of shoots or along the margins or veins of leaves. This takes place mostly in the evening. The larvae hatch after 5-10 days. They molt five times over a 2-3 week period before pupation. The whole development cycle lasts on average 4-5 weeks. The female starts to lay the next generation of eggs within 2-6 days of emerging from the pupa. Under favorable conditions, about 10 generations a year.
N. virescens occurs throughout the rice-growing areas of South-East Asia and in southern Japan. In the tropics, it is able to reproduce all year round. On harvested fields, ratoon rice can serve as a reservoir for the insect. A limited number of other hosts can support development, but this is much slower than on rice. Green rice leafhoppers often occur in very large numbers. However, despite their sometimes high population density, direct feeding damage is not usually the main cause of yield losses. Far more damaging than the insects themselves are the viruses they transmit, especially Tungro disease, which occurs irregularly, but can cause devastating losses. Virus-infected plants show a variety of symptoms, including stunted, deformed leaves, increased tillering, gall formation, and yellowing. The insect has been observed to be more strongly attracted to tungro-infected plants, which makes it a particularly efficient vector.
Integrated Crop Management
The timing of sowing or transplanting is important. Avoiding the peak of the vector's migration can reduce the transmission rate of the viruses that damage mainly young plants.
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