| Cotton bollworm (CBW), Helicoverpa armigera Hiibner, is an important pest in China. Its polyphagy, wide distribution, high fecundity and fitness has led the successive outbreaks since 1992. Although many researches on ecology and forecasting of CBW can be seen recently, the long-range forecasting of the outbreaks of CBW is always a hot potato and only some mid-range (one generation to half year) and short-range (one or two weeks) prediction of the population size of CBW can be carried out. This paper presents some results of my exploratory research on using the advance sea surface temperature (SST) and ENSO indecies as early warning indicators of the outbreaks of CBW, supported by the National Basic Research Project (TG2000016210) and National Research Project for the Tenth Five-year Plan (2001BA50PB01-3).Based on CBW data and climatic data collected over 26 years (1974-1999) in Yuncheng, Shangdong Province, over 22 years (1978-1999) in Dezhou, Shandong Province, and over 20 years( 1980-1999) in Fengxian, Jiangsu Province, the relationship between population density (egg counts) of CBW and anomalies in mean monthly SST and ENSO indices was analyzed to identify significant (p<0.05) correlative key factors with a large and sustainable spatio-temporal extension that could be used to build long-term forecast models for Helicoverpa outbreaks. The ENSO indices used were the Southern Oscillation Index (SOI) and the SST anomalies in five El Nino regions: Nino-l&2 region (N12, 0-10°S, 90-80°W), Nino-3 region (N3, 5°N-5°S,150°-90°W ), Nino-4 region (N4, 5°N-5°S, 160°E-150°W), Nino-Central region (NC, 0°-10°S, 90°-180°W) and Nino-Western region (NW, 0°-15°N, 130°-150°E). Optimum forecast models were established for long-term prediction of 3rd generation egg numbers in Yuncheng and Dezhou, and 2nd generation egg numbers in Fengxian. The results indicate that: The egg amount between each generation show significant (p<0.05) or highly significant (p< 0.01) positive correlation in Yuncheng, and the 2nd and 3rd generation eggs in Dezhou, and the 3rd generation and 4th generation eggs in Fengxian. The egg amount is significant or highly significant positive correlated with monthly mean temperature in the current February and negative correlanted with monthly meantemperature of October in last year.There is a significant (p<0.05) or highly significant (p<0.01) correlation between the fluctuation of CBW populations and SST in the North Pacific. The location and range of the geographical areas involved varied with time, but the correlation in a few areas was relatively stable in space and time.There are a vast number of regions in the North Pacific (p<0.001 in the center) that display a significant correlation between eggs counts of the 3rd CBW generation in Yuncheng, the 2nd CBW generation in Fengxian and SST in January of the following 2 years. These sites ranged from 35°N to 55°N, 135°E to 135°W and the correlation was sustained for 4 months. But the area that showed a significant correlation with 3rd generation eggs in Dezhou was located in the low latitude Northern Pacific (1°-17°N, 165°E-120°W) during July to September in the following 2 years.The evaluation of models with the drive variable of the average of mean SST departures on each grid within significant correlative areas from January to November of the year before last shows that predictive accordant rates for egg counts of 3rd generation CBW in Yuncheng and Dezhou, and 2nd generation in Fengxian, were correct in 5 of the 6 verified years (1994-1999), correct in all 5 years (1995-1999) and in 3 of 5 years (1995-1999) respectively. The results suggest that these models allow the forecasting of CBW outbreaks to be brought forward by about 20~27 months with a good predicitive accuracy of 85% (78 of 91 forecasts correct) with 1995-99 data.We found significant (p<0.05) or highly significant (p<0.01) correlations between changes in CBW populations and ENSO indices. The abundance of CBW eggs was pos... |
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