Experts predict that in 2020, the “two-migration” rice pests will show a resurgence.

Release Date:

2019-11-22

To ascertain the pre-winter population levels of major rice pests and diseases and to refine forecasts for their 2020 incidence trends, the National Agricultural Technology Extension Center organized, from November 11 to 15, a team of experts from plant protection agencies and research‑teaching institutions to conduct surveys in Fangchenggang City, Qinzhou City, and Beihai City, Guangxi. These field investigations yielded a comprehensive assessment of pre-winter populations of key pests, including the “two‑migration” species, providing first‑hand data essential for predicting their 2020 outbreak dynamics.

At present, rice harvesting in Guangxi is 80% complete. The pre-winter pest and disease population levels are generally slightly higher than last year, as evidenced by the following:

First, the overwintering population of “two‑migration” pests and the viral diseases they transmit remained at the same level as last year. Specifically, the average rice planthopper density was 192 insects per 100 hills, with the brown planthopper accounting for 78% of the species and nymphs comprising 70% of the instars. The rice leafroller’s average density was fewer than 10 insects per 100 hills. Meanwhile, southern rice black‑streaked dwarf disease was detected in both unharvested rice fields and regenerating seedlings, with incidence rates in Fangchenggang City generally ranging from 2% to 5%.

Second, the overwintering population of stem borers has been increasing annually, with an average of 30 larvae per mu. Field surveys have detected larvae of the Asian rice stem borer, the Taiwan rice stem borer, the large rice stem borer, and the two-brooded rice stem borer, with the Asian rice stem borer and the Taiwan rice stem borer accounting for the majority (73%).

Third, the pre-winter overwintering population of the rice stem borer is significantly higher than in recent years at this time of year; in particular, in certain severely affected fields in Dazhi Town and Dasi Town of Qinnan District, Qinzhou City, the number of pupae per 100 rice plants ranges from 70 to 140.

Fourth, secondary pests and diseases such as sheath rot, flax leaf spot, tarsonemid mites, and aphids exhibit relatively high initial population levels in certain fields.

During this period, experts also discussed the characteristics and underlying causes of major rice diseases and pests this year, and, drawing on the findings of the current overwintering population survey, they formulated a preliminary forecast of their incidence trends for 2020.

Experts predict that, should weather conditions this winter and next spring remain favorable, rice pests subject to “two‑way migration” will show a resurgence in 2020, with an increasing incidence of localized outbreaks. The stem borer, Chilo suppressalis, will continue to expand its range of severe re‑infestation in the rice‑growing regions of southern China. Sheath blight is expected to occur at moderate to severe levels, though the area of recurrent outbreaks may decline. Epidemic diseases such as blast and false smut are likely to remain generally mild; however, under extreme climatic conditions, there could be a risk of more severe outbreaks. In the south, rice black‑streaked dwarf disease will persist at a generally mild level, though isolated fields may experience concentrated damage.

Experts from research and educational institutions such as South China Agricultural University and the Guangxi Academy of Agricultural Sciences, along with plant protection technicians from provincial, municipal, and county levels, participated in this survey. The event encouraged and facilitated timely baseline surveys of overwintering pest and disease populations across various localities, enabling a comprehensive assessment of the initial pest and disease pressures in rice. Additionally, it provided valuable on-site training and guidance to frontline technical personnel, helping them better understand the patterns of major pest and disease outbreaks and enhance their monitoring skills.

△ Experts conducted on-site surveys to assess the pre-winter baseline levels of rice diseases and pests, and provided training and guidance to local technical personnel.

Source: National Agricultural Technology Center

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