Forecast for the occurrence trend of the first generation of the striped stem borer in rice is released

1. Occurrence level: The first generation of the striped stem borer, the main rice pest in our city, is expected to occur at a moderate-to-severe level, with the affected area in the city reaching more than 250,000 mu, of which more than 50,000 mu are early-planted idle fields.

2. Occurrence period: Moths seen under light on April 11, the beginning of the peak moth emergence period 5/9-12, the peak moth emergence period 5/20-24; the peak egg hatching period 5/27-5/30, the peak period of first and second instar larvae 6/4-6/10, the occurrence period is 3 days later than the average of the past three years.

3. Forecast basis

1. Development progress: This year on 4/28, 107 live larvae were dissected, with a pupation rate of 27.1% and an emergence rate of 2.8%; 2 grade-6 pupae, 3 grade-5 pupae, 2 grade-4 pupae, 5 grade-3 pupae, 5 grade-2 pupae, 6 grade-1 pupae, 11 seventh-instar larvae, 18 sixth-instar larvae, 26 fifth-instar larvae, 20 fourth-instar larvae, 6 third-instar larvae.

2. Overwintering residual larval population: At this station, two overwintering base surveys were conducted on 11/26 last year and 4/2 this year, and two growth-stage surveys on April 18 and April 28. Differences among fields were relatively large. The overwintering residual larvae of the striped stem borer in vacant stubble fields ranged from 4,500-14,600, averaging 7,930 per mu; in wheat stubble fields, 480-780, averaging 570 per mu. The residual larval population decreased by 43-52% compared with normal years. The mortality rate was 16%-21%, 5.9 percentage points higher than the average of the past three years.

3. Weather and seedling conditions: May temperature and rainfall were both normal, with no obvious impact on pupation and emergence of the overwintering generation of the striped stem borer. Our city is a single-season rice area, and the area of seedling fields and early-planted middle rice main fields is relatively small, so the first generation of the striped stem borer is mainly concentrated in seedling fields and some early-planted main fields.

4. Control recommendations

Although the rice leaf roller had a major outbreak last year and widespread pesticide application exerted a certain control effect on the residual population of the striped stem borer, and in addition, the continuous low-temperature rain, snow and freezing weather since January this year has had a certain impact on the overwintering generation population base and mortality rate of the striped stem borer, surveys show that the area of vacant stubble fields is large this year, resulting in many effective pest source fields and a high population base. All localities should attach great importance to the control of the first generation of the striped stem borer, overcome complacency, vigorously control the first generation to suppress the population base, implement taking seedlings to the field with pesticide treatment, and reduce the difficulty of control in main fields.

1. Control timing: At the peak egg hatching period of the first generation of the striped stem borer (5/27-5/30), carry out one comprehensive control treatment on all seedling fields and early-planted main fields; from June 10-13, for some fields that were missed or had poor control efficacy, apply pesticide promptly when the number of dead-heart clumps reaches 50 per mu.

2. Control pesticides: (1) 20% Kangkuan suspension concentrate 10 ml/mu, (2) 4.75% Yinglang 30 ml/mu, (3) 1.8% Lanrui emulsifiable concentrate 75 ml/mu.