First, the trend: In the middle and lower reaches of the Yangtze River and most southern rice-growing areas, the fifth (third) generation of rice leaf rollers is expected to occur with high intensity, reaching more than 300 larvae per 100 square meters in some regions. In northern parts of the Yangtze River and the Huai River region, localized outbreaks are anticipated, with larval densities reaching up to 201–300 per 100 square meters, classified as level 4. The peak hatching period for new larvae is expected to occur between late July and mid-August, aligning with critical growth stages of the rice crop. Second, the forecast basis: 1. Field residue levels are significantly higher than usual. Surveys conducted during late July showed that second-generation rice leaf roller larvae were prevalent across the province. In specific areas such as Huizhou District, Wangjiang County, Guichi District, Dongzhi County, Susong County, Fanchang County, and Fengyang County, residual insect counts reached 230, 298, 176, 220, 202, 320, and 248 respectively. Some locations saw numbers exceeding 200 per 100 square meters, which is the highest recorded since 2000. For instance, Taihu County and Shuyang County had 176 and 220 larvae, respectively—2.44 and 3 times higher than the same period last year. In other regions like Ji County, Ningguo City, Guangde County, Xuanzhou District, Wuhu County, Feidong County, Feixi County, Nanzhao District, and Changfeng County, residual insect levels were also notably higher compared to recent years, with Yuexi County showing a 1.76-fold increase. These high residual populations indicate a strong potential for large-scale infestations in the upcoming generation. 2. Favorable conditions during the outbreak period: 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 an abundant food source for the larvae. Additionally, the field microclimate helps mitigate high temperatures, promoting egg hatching and improving survival rates for younger larvae. These environmental factors contribute to the likelihood of a severe outbreak this season. 3. Larval development is consistent with recent trends. On July 18–19, in Xuanzhou District, 45.1 instar larvae dominated, accounting for 35.19% of the population. In Dongzhi County, 4–5 instar larvae made up 65.21%, closely matching levels observed in recent years. This suggests that the current generation is developing at a typical pace, reinforcing the expectation of widespread occurrence. Towable Backhoes,Mini Backhoe,Backhoe Excavator,Tractor Backhoe,Compact Excavator 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>