The rice brown planthopper has a high capacity to reproduce. Frequently, farmer misuse of insecticide causes outbreaks of hopperburn and/or virus diseases over large areas. The development of biotypes often reduces the life-span of resistant rice varieties. The effectiveness of control by insecticide is lessened because the hoppers are found at the base of plants and the crop canopy acts as an umbrella to protect the insect from spray droplets.
The brown planthopper is mainly a pest of irrigated wetland rice, but it can also become abundant in rainfed wetland environment. It is rare in upland rice.
Development
Five nympha stage
Egg Small nymph Large nymph Adult
Adult. Short winged (brachypterous) and long-winged (macropterous) adult occur is both sexes. Short-winged forms cannot fly but remain in the field to feed and reproduce. Long winged form disperse.
Macropterous females lay about 100 eggs and brachypterous female 300 eggs during a lifetime of about 2 weeks. Openings for eggs are made in the tillers by the saw-like ovipositor.
Adult such the plant sap from the base of plant where they stay day and night. Long-winged adult are highly attracted to a light trap. Highest catches occur during full moon.
A related species, Nilapavarta bakeri (Muir), often confused with the brown planthopper, is found in light trap collection but is not a pest of rice.
Egg. The white eggs are inserted into midrib or leaf sheath in masses of 8-16. Eggs are covered by a dome-shaped egg plug secreted by the female. Red eye spot develop at the head end before the eggs hatch.
Nymph. Nymphs are found near the base of tillers where it is shady and humidity is high. Young nymphs are white, turning brown as they mature. As with leafhopper and planthopper, nymph and adult move laterally like crabs to the opposite side of tillers when disturbed. Nymphs feed on the same tillers in which they hatched and unlike those of other hopper species, can become highly aggregated.
The wing pads of mature nymphs are light brown and opaque; short-winged adults have transparent wings.
Damage
Nymph and adult insert their sucking mouthparts into the plant tissue and remove plant sap from phloem cells. The brown planthopper removes more plant sap than it can digest. The excess plant sap, which is high in sugar, is expelled from the body as honeydew. The honeydew drops fall on the base of plants and in time turn black from infection by a sooty mold fungus.
During the act feeding, the brown planthoppers secrete solid feeding sheaths into the plant tissue to form a feeding tube. The feeding sheaths block the flow of plant sap.
The brown planthopper may remove enough sap or block its flow to cause the tiller to dry and turn brown, producing hopperburn during later growth stage. Hopperburn occurs more rapidly during cloudy weather. Photosynthesis during sunny days allows the plant to recover from sap removal by hoppers.
The brown planthopper also transmits ragged stunt and grassy stunt viruses.
Brown planthopper outbreaks are associated with development of irrigation systems to allow year-round rice cropping (thus continuous planthopper buildup), excessive fertilizer usage results in higher planthopper populations, and the use of insecticides that kill natural enemies.
Plant hosts. The brown planthopper is restricted to rice and wild rices, but reproduction can occur on Leersia hexandra.
Management
Cultural control. Grow no more than two rice crop per year. Crate a rice-free period during the year with early-maturing varieties, plant neighboring field within 3 weeks of each other, and plow down volunteer ratoon after harvest.
Use fertilizer judiciously. Split nitrogen applications three times during crop growth.
To reduce brown planthopper population, drain the field for 3 or 4 days during infestations.
Eliminate virus source in rice and weeds by plowing down stubble.
Plant seedbed in areas as it is possible from light is sources of virus infection. Light attract virus-hatched hopper and weeds is alternative hosts of virus. The virus-carrying hoppers.
Resistant varieties
Planting a resistant variety is effective way of controlling brown planthopper. Brown planthopper numbers decrease on resistant varieties because of the presence of toxic chemicals produced by the plant
Early-maturing varieties to reduce brown planthopper population development.
Higher planthopper population per area occur on high tillering varieties because of the increased plant surface on which to feed.
Biological control
Many parasites, predators, and pathogens attack all stages of the brown planthopper and effectively control this pest under most situations. Improper use of pesticide, however, can kill the natural enemies and thus lead to dramatic brown planthopper outbreaks.
Eggs are parasitized by Anagrus aptabilis (Mymaridae), Paracentrobia andoi (Trichogrammatidae), and Tetratichus formosonus (Uelophid wasps). Cyrtorhinus lividipennis (Miridae) and Amblyseius nr colorai (Phytoseiidae) prey on eggs.
Elenchid strepsipterans, dryinid wasps, and nematodes parasitize nymphs and adults.
Aquatic predators under water surface {Hydrophilus offinis (Hydrophilidae) and Cybister sp (Dytiscidae)} and those that on the surface {(Ranatra dimidiata (Nepidae), Microvelia douglasi atrolineata (Veliidae), Mesovelia vittigera(Mesoveliidae)} prey on hoppers that near the water or fall in the water. Beetles (Microspis crocea, Ophionea ishii) and spider (Callitricia formosana) actively search the foliage for brown planthopper nymphs and adult. Dragon fly (Crocothemis servilia, Agriocnemis femina) prey on moving adults and nymphs.
Fungal pathogens (Beauveria bassiana, Erynia delphacis, Metarhizium anisopliae) infect brown planthopper nymphs and adults. After the death of planthopper, the fungi grow out of the corpses.
Chemical control
Insecticide application
Insecticide to control brown planthopper usually do not necessary in fields to resistant variety.
Apply an effective insecticide on susceptible varieties whenever the brown planthopper population reaches the economic threshold.
Granule are less effective than sprays or dust, particularly when applied to older plants with a greater biomass.
Applying insecticide when the population is mostly young nymphs is useful. Predators normally will lower lower their numbers and young nymphs cannot damage the crop.
Scouting.
Visit the fields weekly from the seedbed to mature grain stage. Pick 20 hills at random across the paddy. Hit each hill several times with the hand and count the number of mature nymphs that fall on the water. Mature nymphs are brown and immature nymphs are white.
