a few years agothe brown plant hooper threatened the cultivation of

1. wheat
2. rice
3. maize
4. milets

correct answer is 2.
The brown planthopper, feeds on rice plants. BPH are among the most important pests of rice, and rice is the major staple crop for about half the world's population. 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, Bhuthan, Burma (Myanmaar), 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.