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Late-maturing Early Rice Rice Crackers
The rice leaf roller, a common pest in rice fields, causes significant damage by feeding on the leaves of rice plants. The larvae roll the leaves into tube-like structures and feed on the epidermis and mesophyll, leading to widespread white leaves. This damage is particularly severe during the later stages of early rice, when the functional leaves are consumed, which negatively affects the development of the basal tillers in late-maturing rice varieties. As a result, this pest has become one of the main factors reducing early rice yields, making timely control essential.
In recent years, the occurrence of rice leaf rollers has been almost annual. Since late June, large numbers of these pests have migrated into the fields. Continuous rainy weather further facilitates their movement, causing serious damage to early rice during its mid to late growth stages. The white leaf rate typically ranges from 20% to 25%, but in some years, it can reach as high as 60% to 70%, with entire fields turning white. If not controlled in time, especially for early and late-season rice, this pest can cause major economic losses.
To manage the rice leaf roller effectively, the strategy should focus on "treating early and controlling small." It is important to monitor the insect population and weather conditions, applying pesticides before the third instar stage of the larvae—ideally at the initial tip of the leaf. This helps reduce the base population and eases the burden of later control efforts. The timing of pesticide application must be precise, as most current formulations are less effective against older larvae. Therefore, it's best to apply treatments during the peak egg hatching period or when young larvae are emerging. For example, when there are 15 or more new leafhoppers per 100 clumps, or when larvae are in the second or third instar, spraying should begin.
In years with early infestations and heavy populations, it’s advisable to apply pesticides during the later rice season. This approach not only controls the damage to early rice but also reduces local pest populations, lowering the pressure for future control efforts—a strategy known as "pre-government control."
When choosing pesticides, it's crucial to use highly effective products that target the mouthparts of the larvae. Spraying should be done at the first leaf stage or two days after the peak egg hatching. Recommended options include: Chlorpyrifos (48% Lactose EC) at 60–100 ml, Fipronil (5% Frigoxysin Suspension) at 40–50 ml, 10% Furanphos Sulfate Suspension at 100–120 ml, 40% Profenofos Cream EC at 100–120 ml, 50% Monosultap Wettable Powder 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 long-term protection for up to 24 days. Even if rain occurs within 12 hours, it won’t affect the effectiveness. Spraying should be done with sufficient water, ensuring the leaves are thoroughly wet. Mist sprayers should be avoided.
By mid-July, most larvae have advanced to a more difficult-to-control stage, making treatment more costly and less effective. If there is a noticeable increase in leaf curling and white leaves, high doses of Avermectin or similar agents can be applied once to minimize damage. Focus on spraying damaged leaves, ensuring thorough coverage and penetration.
In addition to traditional pesticides, newer alternatives such as 5% Buteneflupron Emulsifiable Concentrate, Flufluxthrin (also known as XeroxBao), and Emamectin Benzoate are now available for controlling rice leaf rollers. High-toxicity pesticides can also be used based on market availability and technical guidelines. It’s important to follow safety and environmental regulations while implementing these control measures.