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Late-maturing Early Rice Rice Crackers
The rice leaf roller borer is a serious pest that damages rice plants by feeding on the leaves. The larvae roll the rice leaves into tube-like structures, consuming the epidermis and leaf flesh, which leads to extensive white leaves. This damage is especially severe in the later stages of early rice, when functional leaves are destroyed, affecting the development of late-season basal tillers in late-maturing rice varieties. As a result, this pest has become a major factor in significantly reducing early rice yields, making timely control essential.
In recent years, the rice leaf roller has been a recurring problem, with large numbers of adult moths migrating into rice fields since late June. Continuous rainy weather enhances their migration, leading to significant damage during the middle and late growth stages of early rice. On average, the white leaf rate ranges from 20% to 25%, but in some years, it can reach as high as 60% to 70%. In extreme cases, entire fields may appear completely white. If not controlled promptly, the damage can be devastating, particularly for early and late-season rice, causing substantial economic losses.
To manage the rice leaf roller effectively, it's important to adopt the strategy of "treat early and cure small." Monitoring insect populations and weather conditions is crucial. Pesticides should be applied before the third instar stage of the larvae—ideally when the leaf tip begins to curl. This helps reduce the base population and eases the burden of later control efforts. It’s also important to advance the timing of pesticide application to coincide with the peak egg hatching and young larval stages. Typically, control measures should begin when there are 15 or more new leafhoppers per 100 clumps, or when larvae are at the second or third instar stage.
In years with an early infestation and high population density, it's advisable to apply pesticides during the later rice season. This not only controls the damage to early rice but also reduces local insect populations, lowering the pressure for future control (known as the "pre-government control" strategy).
For effective control, choose high-efficiency insecticides and spray them evenly during the first leaf stage or two days after the peak egg hatching. Recommended options include: Chlorpyrifos (48% EC) at 60–100 ml; Fipronil (5% suspension) at 40–50 ml; 10% Furanofos suspension at 100–120 ml; 40% Profenofos EC at 100–120 ml; 50% Monosultap WP at 100–120 g; and 18% insecticidal double water at 300–400 ml. After spraying, older larvae won't die immediately, but their feeding activity will drop significantly, offering long-term protection for up to 24 days. Even if rain occurs within 12 hours, it won’t affect the effectiveness of the treatment. Spraying should be done with sufficient water to thoroughly wet the leaves, and mist sprayers should be avoided.
By mid-July, most larvae have advanced to a more difficult-to-control stage, making pesticide use less effective and more costly. If the number of curled leaves and white leaves increases significantly, high-dose applications of avermectin or similar agents can be used to minimize damage. Focus on spraying damaged leaves, ensuring thorough coverage and penetration.
In addition, new insecticides such as 5% Buteneflupron emulsifiable concentrate, Flufoxin (also known as XeroxBao), and Emamectin Benzoate are emerging as effective alternatives. High-toxicity pesticides can also be used according to market needs and technical guidelines.
Proper timing, accurate monitoring, and the right choice of insecticides are all critical to managing the rice leaf roller and protecting rice yields.