Causes and Control Methods of Rice Deadheart Disease
Key Points of Rice Dry Seedbed Cultivation Technology 1. Apply sufficient base fertilizer: In combination with deep ploughing or leveling the field with irrigation water, apply 30-40 kg of rice-specific compound fertilizer, ammonium bicarbonate and 20-25 kg of ordinary calcium superphosphate per mu, applied all at once as a middle fertilizer. Fields with broad bean as the previous crop should receive a larger amount, while vegetable or potato fields should receive a smaller amount. 2. Transplant shallowly and sparsely at the right time...
During the growth of rice, diseases or insect pests often cause "deadheart". Correctly determining the cause of rice "deadheart" and promptly taking targeted measures for its control is an effective measure to ensure high and stable rice yields. I. Simple Diagnosis of Rice "Deadheart"
1. "Deadheart" caused by insect pests. The larger rice borer, the striped stem borer, the yellow stem borer, the mole cricket and others can all cause "deadheart" when they damage rice. Their main differences are as follows: The symptoms of damage by the larger rice borer are large borer holes and abundant frass, with the frass generally deposited between the rice leaf sheath and the stem. The leaf sheaths and leaves of the damaged rice stems all turn yellow. The damage is more severe at the edges of the paddy field and lighter in the middle of the field.
The damage by the striped stem borer is shown as follows: after the eggs hatch, the young borers first gather on the inner side of the rice leaf sheath to feed and cause damage. Water-soaked yellow spots first appear on the outside of the damaged leaf sheath, which then gradually turns yellow and dies. After the young borers grow slightly larger, they bore into the rice stem, causing the tip of the rice flag leaf to turn yellow, and in severe cases the central leaf dies. There are borer holes on the bored rice stems, with little frass outside the holes and more frass inside the holes.
The damage by the yellow stem borer is shown as follows: the young borers first gnaw on the rice central leaf, causing the central leaf to lose water and roll up longitudinally like a scallion tube, appearing greenish-white, commonly known as "false deadheart". When the curled central leaf is pulled out, a neat cross-section can be seen. If the borers continue to cause damage, bite through the central leaf and destroy the growing point, then the central leaf completely dies, becoming "true deadheart". The borer holes on the bored rice stems are relatively small, with no frass outside the holes and white fine granular frass inside the holes.
When mole crickets damage rice, they often bite off the rice clump partially or entirely from the base, causing the rice central leaf to turn yellow and die. The damaged rice can easily be pulled up as a whole plant, and there are no borer holes or frass on the rice stems. This type of deadheart generally occurs only when the paddy field is being dried, or due to long-term drought and lack of water in the paddy field.
2. "Deadheart" caused by diseases. Rice virus diseases and bacterial leaf blight can both cause rice "deadheart". The difference between the two is: the "deadheart" symptoms caused by virus diseases are similar to the deadheart caused by the yellow stem borer, but there are no borer holes or frass on the rice stems, the central leaf is not easy to pull out, and when the leaf is squeezed between glass slides there is no bacterial ooze.
The "deadheart" caused by bacterial leaf blight occurs mostly at the rice tillering stage. After onset, the central leaf or the 1-2 leaves below the central leaf of the diseased plant first lose water, curl, turn green-wilt and become necrotic, then the other leaves also gradually curl and turn green-wilt, and finally all the leaves of the whole plant die. Take a small piece of fresh diseased leaf, squeeze it between glass slides, and examine it against the light; yellow bacterial ooze can be seen flowing out at the openings of the leaf veins.
II. Control Measures for Rice "Deadheart"
For "deadheart" caused by damage from stem borers, symptomatic insecticides such as fipronil, teshaming and chongcuo can be sprayed for control.
For deadheart caused by damage from mole crickets, when the paddy field is drained for drying, poisoned bait such as wheat bran mixed with trichlorfon can be used to trap and kill them.
For deadheart caused by virus diseases, rice seeds should be soaked with strong chlorine essence before sowing, and control of virus-carrying insects such as rice planthoppers and leafhoppers should be carried out well.
For deadheart caused by bacterial leaf blight, in addition to doing a good job of disinfecting rice seeds, symptomatic agents such as shibaoling and yekuning should be sprayed promptly at the early stage of bacterial leaf blight onset for control.