Witchuda Rattanakarn and Pamorn Pattawung
Bureau of Rice Research and Development, Rice Department, Bangkhen, Thailand, and
Phitsanulok Rice Research Center, Rice Department
On December 24, 2009, we traveled to 11 sites in three provinces, Khampaengphet, Pichit and Pitsanulok, interviewed farmers and made field assessments of damages caused by brown planthopper (BPH) and the two viruses it transmits, the rice ragged stunt virus (RRSV) and the rice grassy stunt virus (RGSV). All the 11 sites had hopperburn symptoms and virus infections varied from 5% to 70%. The farmers were using improved traditional varieties, Suphan Buri 4 and Patum Thani 1 and have been using broad spectrum insecticides, abamectin and dinofefuran. These insecticides have poor effects on BPH but have strong effects on the aquatic animals, bees and natural enemies. But farmers use it anyway because they were advised by the local pesticide salesmen. Below are details of our observations:
In Ban Meunjan, Meoung district, farmer, Pin Yodpetch grew traditional varieties, Po Ngern and Po Thong. Signs of hopperburn appeared in the heading stage. He had tried to control the BPH using abamectin with no effects. In addition his crop had about 10% virus infection.
In Ban Meunjan Meoung district, farmer Prateung Pumpuong, grew Khao Phatum and sprayed his crop using with dinotefuran to control BPH but it did not work. His crop suffered hopperburn and about 5% infections by the viruses. In addition his field also had heavy blast infections.
In Bang Ragam district, the traditional rice varieties, Po Ngern and Po Thong, had severe hopperburn destroying 8 -10 ha. The farmers had harvested and the stubbles showed virus infection symptoms.
In another location in Bang Ragam district, rice was close to harvesting and about 5% of the crops had virus infection symptoms.
In Bang Kratum district, farmers grew Suphan Buri 4, and at the tillering stage, they sprayed abamectin. About 5% of the crop was infected with the viruses.
In Ban Tong Maharach, Sai-ngarm district, the crop was in the heading and flowering stages. Nymphs and adult BPH populations were in low densities and 5% of the crop was infected with the viruses.
The rice crop in Bann Nerngroi, Sai-ngarm district, was in the tillering stages. BPH was low but about 70-80% of the crop was infected.
In Sai-ngarm district,the rice was in the heading stage and large densities of BPH nymphs were found in the crop. Hopperburn has occurred in neighboring fields and the crops were severely infected with viruses.
Rice was in the booting stages in Vachirabaramee district, virus symptoms were found in about 10 % of the crop.
In Sam Ngam district, farmers were growing a local variety called poung thong. The crops was in the booting and flowering stages. Low densities of BPH were found in the crops and about 10% had virus infection symptoms.
Farmers in Bang Ruong Chang, Mueong district, grew Suphan Buri 4 and there was abundance of plants with virus infection symptoms.