According to the Vietnamese Ministry of Agriculture and Rural Development, a new brown plant hopper, known as laodelphax striatellus, has been found densely scattered over 35 hectares (ha) of rice fields in the northern province of Hung Yen, Hai Duong, Thai Binh, and Bac Ninh. Viet Nam News reports that average infestations are up to 4,000 - 6,000 insects per square meter, while in some areas, the highest density is 18,000 - 20,000 insects per square meter. The brown plant hopper -- said to be the most serious of rice pests -- has infested several other countries like mainland China, Japan, and South Korea, according to Ngo Tien Dung, head of the Plant Protection Division of the Department of Plant Protection. The insects suck rice plant sap and transmit rice diseases, leaving fields susceptible to the ragged stunt rice disease, rice stripe virus, and maize rough dwarf disease.

The pests are said to be responsible for damage to 20,000 ha of winter-spring rice crop, of which some 3,000 ha is seriously affected. More than 30,000 ha of summer-autumn crop in southern areas have also been affected by this insect.

Agriculture officials are advising farmers not to panic and are warning farmers against using too much pesticide, which could kill beneficial insects as well as the harmful ones. The ministry has asked provincial authorities to supervise the situation and take action, strengthening communication and training for technical staff and farmers in effectively applying preventative measures. Ngo said the insects could be controlled if farmers apply integrated pest management (IPM) in rice growing.

"It is highly unusual that brown plant hoppers appear in such large numbers," said the director of the Cuu Long Delta Rice Research Institute, Dr. Le Van Banh. He said when the summer-autumn crop which sheltered the insects were harvested, the hoppers moved to other places. Le predicted that the scourge of pests would end in a few days without affecting the summer-autumn crop.