by Yoohan Song
Gyeongsang National University
Jinju, 660-701, Korea
Another important planthopper pest of rice is the smaller brown planthopper (SBPH) Laodelphax striatellus, which is mainly found in temperate rice areas. In China this pest is becoming increasingly damaging and populations of SBPH are becoming highly resistant to insecticides. Recently the pest was reported to occur in large densities in the Red River Delta of Vietnam.
The Rural Development Administration (RDA) of Korea recently reported that all 10 counties along the western coastal area of the Korea peninsular were hit by a swarm of SBPH and were transmitting rice streak virus and black streak dwarf virus disease to rice. High populations of densities, 20 to 40 per hill, were seen on the crops transplanted a week ago. The aerial net trap catches were as high as 963 adults at Tae-Ahn county surveillance station in a few days from June 3, 2009. This is the highest ever recorded. They were also found in Seo-San (65), Bo-Ryeong (32), Seo-Cheon (919), Gun-San (67), Bu-Ahn (597), Yeong-Gwang (150), Shin-Ahn (805), and Jin-Do (155) (see map).
The SBPH were believed to be from a huge flux of immigrants from China, probably carried by the high winds brought about by the weather front passing through the region. High peaks of the aerial traps in the western coast could be linked to the weather depressions in the area at the same time, while there were no sharp aerial trap peaks in other parts of Korea. The barley fields, the possible local sources of SBPH, in the area had been cleared and transplanted with rice plant two weeks ago and thus there was no local source of the hopper. The provinces of Jiangsu and Zhejiang in China were in the middle of the wheat harvesting period, probably source of the SBPH. Similar sharp SBPH flights were also observed in two provinces. We are now analyzing genetic background of the SBPH samples, both in China and Vietnam as well.