According to the investigation of the source base of rice borer borer (three borers and dihua borers) after winter, combined with the agricultural conditions and climatic characteristics of our region, with reference to historical data analysis, it is expected that the incidence of the first generation of rice borer borers in the whole region is light and moderate, which is the same as that of the same period last year; the occurrence of secondary borers in local rice areas shows an upward trend. The main areas of the first generation of triad borers are in central Guizhou and most of western Guizhou, the Right River Valley and parts of southern Guizhou; the occurrence period is mostly close to that of the previous year and perennial; the first generation of adult insects in the rice area of southeast Guizhou is in mid-March to mid-April; and other rice areas are from late March to late April. The main occurrence areas of the first generation of dimorph borers are in the rice areas of northeast Guizhou and west Guizhou; the peak period of the first generation of adult insects is from mid-April to early May in the rice area of northeast Guizhou, and from early to late April in the rice area of western Guizhou. Borer moths are mainly concentrated in seedling fields and early transplantation of fields to lay eggs and cause harm.
First, the main basis
(1) The area of effective insect sources
In 2020, the occurrence area of sanhua borer and dihua borer in the whole region was 171.40 and 2.2301 million mu, respectively; the area of sanhua borer was reduced by 14.29% and 49.68% respectively compared with the previous year and the perennial year; and the area of the secondary borer was increased by 7.44% and 10.30% respectively over the previous year and the perennial year, respectively.
(2) The base of insect sources after winter
Compared with the same period last year, the weighted average residual insect volume after winter was relatively small, and the secondary borer was basically flat. According to statistics, the weighted average population density of various types of insect remnants in 59 counties (cities, districts) such as Heshan was 80.00 heads/mu, which was 20.06% and 56.98% lower than that of the same period last year and the same period of the previous year. According to statistics, the weighted average population density of insect populations of various types of erhua borers in 14 counties such as meltwater was 3427.00 heads/mu, which was basically the same as that of the same period last year; the counties of Pingle, Huanjiang, Sanjiang, Tianyang and Nandan increased significantly over the same period of the previous year, of which the weighted average residual insect volume of various types of erhua borers in Pingle County (15222.2 heads/mu) was 1.86 times that of the same period last year.
(3) Climatic factors
In January 2021, the average temperature of the whole region was 11.6 °C, close to the normal year, and the average precipitation was 3.8 mm, which was 92.4% less than the same period of the year, the second smallest in the same period of history since 1951. The average temperature in February was 16.9 °C, 3.8 °C higher than the same period of the year, the third highest since 1951, and the average precipitation was 70.5 mm, 20% more than the same period of the year. The overwintering mortality rate of Sanhua borer in most rice areas was flat to increase from the previous year, and the weighted mortality rate of various types of fields in 52 counties (cities, districts) such as Xiangzhou was 8.19%, 2.89% higher than the same period last year and 13.88% lower than usual. According to statistics, the mortality rate of dilated borer overwintering in 32 counties (cities, districts) such as Pingle was 5.05%. The mortality rate of the overwintering generation of the two borers is significantly lower than that of the three borers, and the statistics of 19 counties (cities, districts) such as Huanjiang are 2.60% for the two borers and 8.27% for the three borers.
(4) Agricultural activities
As of March 12, 12.853 million kilograms of early rice seeds have been impregnated in the whole region, of which 8.3387 million kilograms of hybrid rice seeds and 364,800 mu of early rice seedlings have been planted. In addition to the two cities of Guilin and Liuzhou, all other cities in the whole region have begun early rice seedling work. The area of early rice has been planted in the whole region of 248,000 mu, and early rice planting has begun in 6 cities of Nanning, Wuzhou, Beihai, Qinzhou, Guigang and Yulin.
II. Opinions on prevention and control
From mid-March to mid-April, as a critical period for the prevention and control of the first generation of rice borer borers, plant protection technicians at all levels should go deep into the field to conduct classified guidance and prevention according to local insect conditions.
(1) Agricultural prevention and control
Guiding the peasant masses to seize the opportunity to irrigate water during the physiological transition period of borer overwintering larvae (that is, the initial stage of pupa pupae) can greatly reduce the overwintering base of borers; use machine farming to accelerate the decay of grass borers and improve the effect of killing borers; and guide farmers to manually remove borer egg blocks such as three borers and dilated borers in the rice fields and reduce the base of insect sources. No-till rice fields should be irrigated and flooded early to ensure that the grass rots.
Do a good job of physical barrier seedlings. The use of 30 mesh insect control net or 15 to 20 g/m2 non-woven fabric to cover the whole process of seedling breeding, block the mesosome insects, prevent the southern black stripe dwarf disease and other viral diseases; and can prevent seedling rice thrips, leafhoppers, etc.; can also prevent borers and other eggs on rice seedlings.
(2) Biological control
Insect traps are used at the adult stage of each generation, the red-eyed wasp of rice borer is released at the initial stage of the moth, and the control of Bacillus thuringiensis (Bt) is applied at the peak of egg incubation. Note that Bt is highly toxic to silkworms, and should be used with caution in the rice fields adjacent to mulberry gardens.
(3) Prevention and treatment of pharmaceutical agents
When the control targets are reached (when the number of eggs per mu of the three borers reaches 100 pieces per mu (1000 seedlings); when the sheath rate of the two borers is 4% and 3% in the morning and evening rice tillering stages, and when the yield of bush damage is 1% (plant damage rate is 0.1%)) at the panicle stage, the disease should be treated in a timely manner.
Do a good job of seed treatment and transplanting with medicine. For diseases and insects at the seedling stage such as malignant seedling disease, seedling plague, virus disease, nematode disease, rice planthopper, rice thrips, borer, etc., the medicinal seed is mixed or soaked to reduce the use of drugs at the seedling stage and the early stage of the field. 3 days before seedling transplanting, transplanting with medicine to prevent borers, leaf blast, rice thrips, rice planthoppers and leafhoppers and their transmitted viral diseases.
(Source: Guangxi Zhuang Autonomous Region Plant Protection Station)