by
Jiaan Cheng
Professor, Zhejiang University
Hangzhou, PR China
Map showing the province of Yunnan and counties infested (in red)
Yunnan province is situated in the Southern Western part of China. The main agricultural activity there is tobacco but rice is an important food crop grown in about 1 million ha. Their average rice yield is 6 tons/ha and most farmers have adopted hybrid rice varieties.
A: Rice fields with spots of hopperburn. B: Close-up of plants serious affected by WBPH feeding. C: Close-up of WBPH on leaf
Early planthopper immigrants were observed in March 2009 which was about 10 days earlier than usual in Yunnan and 99% of them were WBPH. The highest daily records under light traps in Jinping and Jiangcheng counties were 92,400 on May 6 and 65,368 on April 16, respectively. The total catches under light traps from March to Mid-May in the two counties were 0.1-0.2 millions and were the highest ever recorded.
Dead WBPH on the water surface. B: A pile of WBPH caught in one light trap a night.
The infested areas included 56 counties in the southern part of Yunnan (close to Vietnam, Laos and Thailand). Total areas infested with high WBPH densities of about 10 to 30 per hill were about 6 millions Mu (~ 400,000 ha) and the insecticide control areas were more than 10 millons Mu. The highest density observed was 525 hoppers per hill.
Prof Cheng
The pictures show crops at very young stages being damaged by WBPH. Does this mean that the WBPH infesting the southern districts of Yunnan were immigrating adults? And if so do you think this was due to mass displacement from another place? And where?
Yes. The picture show damages of rice seedlings caused by WBPH adults and these adults were immigrants since it is not possible for the WBPH to develop a generation seedling stage. The possible source area of these immigrants may be from somewhere in Vietnam, Laos, Mynmar or Thailand because the infesting areas in Yunnan were at the border of these countries and the prevailing winds at that time were from south to north. There were no WBPH source in China at that time. I will be happy to get more information on WBPH problems in these possible source areas. J.A. Cheng
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