Ann: POSITIVE RESULTS FOR FLAVOCIDE WITH MAJOR RICE PEST, page-21

Brown planthopper

The brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) is a planthopper speciesthat feeds on rice plants (Oryza sativaL.). BPH are among the most important pests of rice, and rice is the major staple crop for about half the world's population.[1] They damage rice directly through feeding and also by transmitting two viruses, rice ragged stunt virus and rice grassy stunt virus. Up to 60% yield loss is common in susceptible rice cultivars attacked by BPH. The BPH are distributed in: Australia, Bangladesh, Bhutan, Burma (Myanmar), Cambodia, China, Fiji, India,[2] Indonesia, Japan, North and South Korea, Laos, Malaysia, Nepal, Pakistan, Papua New Guinea, Philippines, Sri Lanka, Taiwan, Thailand, and Vietnam. Their host plant other than rice is Leersia hexandra.


DAMAGE


BPH[3] infest the rice crop at all stages of plant growth. As a result of feeding by both nymphs and adults at the base of the tillers, plants turn yellow and dry up rapidly. At early infestation, round, yellow patches appear, which soon turn brownish due to the drying up of the plants. This condition is called 'hopper burn'. Temperature is a critical factor in the life activities of the insect. The hatchability and survival rate are the highest around 25 °C. Eggs are very sensitive to desiccation and soon shrivel when the host plant starts wilting. The population growth of brown plant hopper is maximum at a temperature range of 28 to 30 °C.

Excessive use of urea as nitrogenousfertilizer and insecticides can lead to outbreaks by increasing the fecundity of the brown planthopper, and by reducing populations of natural enemies.[4][5][6] In 2011, the Thai government announced an initiative to address brown planthoppers that included restricting the use of outbreak-causing insecticides including abamectin and cypermethrin - the decision was supported by the International Rice Research Institute (IRRI).[7] IRRI also outlined recommendations in an action plan to help smartly manage planthopper outbreaks.[8] In December 2011, the IRRI held a conference in Vietnam to address the threats of insecticide misuse and explore options for mitigation.[9]