Timely Control of the Rice Leaf Roller Is Essential and Cannot Be Delayed

The rice leaf roller is one of the major rice pests in our province. Its larvae damage the leaves, turning rice leaves into a mass of withered white. Especially when it attacks at the booting or heading stage, it will cause a sharp decline in rice yield. This pest has seven generations a year, and the second-generation larvae are the most numerous and cause the most serious damage to early rice. If control is not timely, it will break out in a major outbreak during the heading period, causing incalculable losses.

For forecasting the rice leaf roller, the appropriate control timing should be determined based on the forecast of the occurrence period. Based on past conditions, investigation should begin 4 days after the peak of the moth flight, once every 2 weeks, closely monitoring the progress of larval occurrence. When the 1st to 2nd instar larvae account for about 70% of the total, or there are about 15 leaf rolls per 100 hills of rice, this is the appropriate control timing. Because this is exactly the peak hatching period of the larvae, and the time to act is when the larvae are at their weakest resistance to pesticides during the peak hatching period, and also when the larvae are concentrated at the base of the leaf sheath to feed. If the pesticide is sprayed as much as possible onto the base of the leaf sheath, most of the larvae can be killed, and the effect is the best. If the pesticide is sprayed late, the larvae have already rolled into the leaf tube, and the application effect will be poor.

To achieve the best control effect against this pest, it is essential to select the appropriate pesticide for spraying. During the peak hatching period of the larvae, you can use 200 ml of 25% bisultap aqueous solution plus 50 ml of 40% dimethoate emulsifiable concentrate or 100-125 ml of 20% imidacloprid emulsifiable concentrate, diluted with 60 kg of water for spraying, and the control effect is relatively good.