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In the process of rice cultivation, one common problem that farmers often encounter is the occurrence of "dry heart," which can be caused by diseases or pest infestations. Accurately identifying the cause of the dry heart and taking timely, targeted measures to manage it are essential for ensuring high and stable rice yields.
First, let's look at the simple diagnosis of rice "dry heart."
1. Dry heart caused by insect pests: Different pests can lead to this condition, and each has distinct symptoms. For example, stem borers such as the rice stem borer, the brown planthopper, and the Sanhua cricket can all cause damage. The affected stems, leaves, and sheaths turn yellow, with more severe damage near the edges of the field rather than in the center.
The larvae of the rice stem borer typically hatch inside the leaf sheaths and feed on them, causing water-soaked spots that eventually turn yellow and die. As the larvae grow, they move into the rice stem, causing the flag leaf tip to yellow and, in severe cases, leading to the death of the heart leaves. You may notice small holes in the stalks, with few insects outside the hole and more inside.
The Sanhua cricket, on the other hand, feeds on the heart of the rice leaf first, causing dehydration and a "false dry heart" appearance, similar to an onion tube. The curled heart is neatly cut, and if the damage continues, the growing point can be destroyed, resulting in a true "dry heart." The stem borers of japonica rice are smaller, and there are no visible feces outside the holes, only fine white droppings inside.
Drought can also cause dry heart. In this case, the base of the rice stalk becomes yellow and weak, making the plant easy to pull out. There are no wormholes or insect feces on the stems. This type of dry heart usually occurs during periods of prolonged drought or when the field lacks sufficient water.
2. Dry heart caused by disease: Viral infections and bacterial leaf blight are two common causes. The symptoms of viral-induced dry heart resemble those caused by the Sanhua cricket, but there are no wormholes or insect excrement on the stems. The heart blade is difficult to pull up, and when pressed between glass slides, it produces a milky bacterial ooze.
Bacterial leaf blight typically affects the tillering stage of rice. Infected plants show water-soaked, curled, blue, and dry leaves, followed by necrosis. As the disease progresses, other leaves curl and dry out, eventually leading to the death of the entire plant. When a fresh diseased leaf is squeezed between two glass slides, a yellow bacterial exudate can be seen along the vein margins.
Second, prevention and control measures for rice "dry heart":
For dry heart caused by insect pests, insecticides like Ruijint or specific larvicides can be applied to target the pests effectively.
When earthworms cause the dry heart, poison baits made from wheat bran mixed with trichlorfon can be used when the rice is flooded.
To prevent dry heart caused by viral diseases, rice seeds should be soaked in strong chlorine before sowing, and proper control of pests like planthoppers and leafhoppers is crucial.
For bacterial leaf blight, in addition to seed disinfection, applying Shibaoling and Yekuning during the early stages of the disease can help manage the issue effectively.