First, the trend: In the middle and lower reaches of the Yangtze River and most southern rice-growing areas, five (3) generations of rice leaf rollers are expected to occur, with more than 300 larvae per plexus in some regions. In the northern parts of the Yangtze River and the Huai River basin, the occurrence will be more localized, reaching level 4 with 201–300 larvae per plexus. The peak period for newly hatched larvae is anticipated between late July and mid-August across most rice-growing regions. Second, the forecast basis: 1. Field residue levels are currently high. Surveys conducted in mid-to-late July showed that second-generation rice leaf roller larvae were prevalent across the province. In Huizhou District, Wangjiang County, Guichi District, Dongzhi County, Susong County, Fanchang County, and Fengyang County, the residual insect counts reached 230, 298, 176, 220, 202, and 320 respectively. Some areas, such as Taihu County and Shuyang County, recorded 176 and 220 larvae per plexus, which were 2.44 and 3.0 times higher than the same period last year. In Ji County, Ningguo City, Guangde County, Xuanzhou District, Wuhu County, Feidong County, Feixi County, Nanzhao District, and Changfeng County, the numbers were also significantly higher compared to recent years, with Yuexi County recording 49 larvae—1.76 times the previous year’s level. These high residual numbers indicate a strong potential for a severe outbreak of the third generation of rice leaf rollers. 2. During the peak occurrence period of the third generation, food availability is abundant, and field microclimates are favorable for the pests. From late July to early August, most single-crop rice is in the booting to heading stage, while late-season rice is in the tillering phase. This provides ample feeding conditions for larvae, and the dense canopy helps maintain humidity, which supports egg hatching and larval survival. The current weather conditions are also less extreme, reducing stress on young larvae. 3. Larval development aligns with recent trends. On July 18–19, in Xuanzhou District, 45.1 instar larvae dominated, accounting for 35.19%, while in Dongzhi County, 4–5 instar larvae made up 65.21% of the population, closely matching the patterns observed in recent years. This consistency suggests that the outbreak may follow a similar timeline and intensity to previous seasons. Drum Mower,Pto Drum Mower,Drum Mower Prices,Drum Mower For Tractor,Disc Mower,Rotor Mower Changzhou Kafurter Machinery Co., Ltd , https://www.kafurter.com
Prediction of the Occurrence Trend of Rice Leaf Rollers in Five (3) Years in Anhui Province in 2007