Species composition and seasonal abundance of pestiferous plant bugs (Hemiptera: Miridae) on Bt Cotton in China

Only recently, due to a major reduction of broad-spectrum insecticide use in transgenic (Bt) cotton in China, plant bugs (Heteroptera: Miridae) have emerged as key pests of this crop. To determine their species composition and seasonal activity at various locations nationwide, field surveys were carried out between 2002 and 2006, using sweep-net samples and visual observation. Surveys were conducted in three major cotton-growing regions: Changjiang River, Yellow River, and Northwestern Region. The mirid complex on Bt cotton basically consisted of five different species, with Lygus lucorum, Lygus pratensis, and Adelphocoris suturalis most commonly encountered. L. lucorum and A. suturalis were the dominant species in the Changjiang River and Yellow River Region, while L. pratensis was the most common species in the Northwestern Region. The various mirid species were found in cotton fields throughout the cotton-growing season, usually with great population densities during the squaring and flowering stages. Peak mirid abundance ranged from 50 to 200 per hundred plants. Given the comparatively low economic thresholds for mirids (approx. 10 individuals/100 plants), these insects constitute serious pests in all cotton-growing regions of China. This paper suggests that L. lucorum, L. pratensis, and A. suturalis should be treated as the main targets for developing pestiferous mirid forecasting and management strategies, which would be defined at or prior to the flowering and squaring stages of cotton in China.