The rice leaf roller borer is a serious pest that damages rice crops by feeding on the leaves. The larvae roll the leaves into tube-like structures, consuming the epidermis and leaf flesh, which leads to a large number of white leaves. This damage is particularly severe in the later stages of early rice, when the functional leaves are damaged, affecting the development of the late-season basal groats in late-maturing rice. As a result, this pest has become a major factor in reducing early rice yields, making timely control essential.
In recent years, the occurrence of the rice leaffolder has been almost annual. Since the end of June, large numbers of adult insects have migrated into rice fields. Continuous rainy weather promotes their movement, leading to significant damage during the mid- to late growth stages of early rice. The white leaf rate typically ranges from 20% to 25%, but in some years, it can reach as high as 60% to 70%. In extreme cases, entire fields may be completely whitened. If not controlled promptly, the damage can be especially devastating for early rice, and even more so for late-season varieties, resulting in major yield losses.
To effectively manage the rice leaffolder, the strategy should focus on "treating early and dealing with small issues." It is crucial to monitor insect populations and weather conditions, applying pesticides before the third instar stage of the larvae—when the leaf tips begin to curl. This helps reduce the base population and eases the pressure of later-stage control efforts. Timing is key, as most current pesticides are less effective against older larvae. Therefore, it's recommended to apply treatments earlier, targeting the peak egg-hatching period or the early larval stage. For instance, when there are 15 or more new leafhoppers per 100 clumps, or when second- or third-instar larvae are observed, it’s time to take action.
In years with early infestations and heavy infestations, using preventive sprays in the later stages of rice can help control both early and late-season damage. This approach, known as "pre-government control," not only reduces immediate harm but also lowers the local insect population, easing the burden of future treatments.
When choosing pesticides, it's important to select highly effective options. Spraying should be done at the first leaf stage or two days after the egg-hatching peak. Recommended options include: Chlorpyrifos (48% EC) at 60–100 ml, Fipronil (5% suspension) at 40–50 ml, 10% Furanphos Suspension at 100–120 ml, 40% Profenofos EC at 100–120 ml, 50% Monosultap WP at 100–120 grams, and 18% Insecticidal Double Water at 300–400 ml. After spraying, older larvae may not die immediately, but their feeding activity will significantly decrease, offering protection for up to 24 days. The treated leaves remain protected longer than newly grown ones, and the effectiveness is not affected if rain occurs within 12 hours of application. Spraying should be done with sufficient water, ensuring full coverage of the leaves. Mist sprayers should be avoided.
By mid-July, most of the field larvae have advanced in age, making control more difficult and expensive. If the number of curled leaves and white leaves increases significantly, high doses of Avermectin or similar agents can be applied in one go to reduce the impact of the rice leaffolder. Focus on spraying the affected areas thoroughly, ensuring penetration.
Newer pesticide options include 5% Buteneflupron EC, Flufluxthrin (also known as XeroxBao), and Emamectin Benzoate. These provide additional choices for farmers. High-toxicity pesticides can also be used, provided they meet technical guidelines and market requirements.
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