|Scientific Name||Nilaparvata lugens (Stål)|
|Common Names||English: Brown planthopper; German: Braunrückige Reiszikade; Spanish: Saltahoja del arroz; French: Cicadelle brune; Indonesian: Wereng; Japanese: Tobiiro-unka|
Adults occur in macropterous (long-winged) and brachypterous (short-winged) forms. The macropterous form is about 3.5 - 4.5 mm (0.14-0.17 inch) in length.
The body is brown, and the wings are transparent, with very conspicuous veins.
Young nymphs are white, but they gradually become darker in older instars.
Both nymphs and adults penetrate the tissues of their rice host plants with their piercing-sucking mouthparts in order to ingest phloem-sap. Loss of nutrients and obstruction of vessels cause yellowing of leaves. Later, the plants wilt, gradually drying up and eventually dying off. An increasing population density of planthoppers eventually leads to so-called „hopperburn“: groups of dead plants appearing as brown and often lodged patches in the rice field; these patches continue to grow as the insect spreads.
Less severe infestations can still result in reduced plant vigor, smaller panicles, fewer ripened grains and lower grain weight. In addition to the direct damage it causes, the brown planthopper is an important vector of rice grassy stunt virus and rice ragged stunt virus.
All stages of N. lugens excrete honeydew, thus promoting the growth of sooty mold.
The insect prefers to feed on leaf blades and leaf sheaths at the base of plants, where it is shaded and humidity is high. Damage is generally greater in the wet season than in the dry season.
Macropterous females migrate into rice fields shortly after transplanting, laying groups of 5-15 eggs into the sheaths or midribs of leaves. The first instar nymphs hatch after 5-9 days; they molt five times during a period of 2-3 weeks. Initially, most of them develop into brachypterous adults: but as population density increases, or if food becomes scarce, the proportion developing into the macropterous form increases. During their adult lifespan of 10-30 days, macropterous females each produce about 100 eggs, brachypterous females 300 to more than 700.
In the tropics, N. lugens is active all year round, and produces 3-6 generations per crop. It is not able to overwinter in temperate regions, so it migrates into these areas in the spring, often after traveling long distances.
N. lugens is found in all of the rice-growing countries of Asia, on many Pacific islands, and in the tropical part of Australia.
It is one of the most serious insect pests of rice. Yield losses of 30% are not uncommon, and sometimes the crop can be destroyed completely.
Useful non-chemical contribution to Integrated Weed Management
Natural predators play an significant role in checking populations of N. lugens, so pesticide products should be chosen and applied within the framework of an IPM programme.
Monitor rice fields carefully: infestation can be kept under control with the use of suitable products. Draining rice fields for 3-4 days can also help to reduce infestation. High doses of nitrogen fertilizer indirectly promote the development of this pest. Maintaining a rice-free period between crops can interrupt an otherwise continuous population build-up.
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