Rice dwarf disease

The symptoms were mainly distributed in the southern rice area. Also known as rice common dwarf disease, general dwarf, green dwarf and so on. After the rice was susceptible from seedling stage to tillering stage, the plant was dwarfed, the tillers increased, the leaves were thick green and stiff, and the diseased rice could not heading and fruiting in the later growth stage. The symptoms of diseased leaves can be divided into two types. The white spot type appeared dotted yellow-white spots parallel to the leaf vein on the leaf blade or on the leaf sheath, especially at the base. Dots appeared in the new leaves above the initial diseased leaves, but not in the following old leaves. In the twisted type, in the case of lack of light, the extraction of the heart leaf is twisted, and with the extension of the heart leaf, the edge of the leaf appears wavy notch and the color is yellowish. When the disease occurred at booting stage, white dots appeared on the flag leaf leaf and leaf sheath, and the panicle neck was shortened, forming a necked or semi-necked panicle.

The pathogen Ricedwarfvirus is referred to as RDV, which is called rice dwarf virus, which belongs to plant reovirus group virus. The virion is spherical polyhedron with equal diameter symmetry, 75nm in size and double stranded ribonucleic acid in the virion. The virus passivation temperature was 40-45 ℃, the dilution limit was 1000-100000 times, and the in vitro survival time was 48 hours. Buccal toxins are mainly concentrated in the chlorotic part of diseased leaves. In the white spotted leaf cells, there are nearly spherical X bodies containing empty cells.

The virus can be transmitted by black-tailed leafhopper, two black-tailed leafhopper and electric leafhopper. Mainly black-tailed leafhopper. The infected leafhopper can transmit virus all its life and can be transmitted through eggs. The black-tailed leafhopper absorbs sweat on diseased rice and takes the shortest time to get poison. After acquiring the virus, it takes a period of recurrent period to transmit the virus, which is 17 days at 20 ℃ and 12.4 days at 29.2 ℃. The incubation period from seedling stage to tillering stage was shorter than that from seedling stage to tillering stage, and then prolonged with the increase of age. The temperature of seedling stage was 22.6 ℃, the incubation period was 11-24 days, and 28 ℃ was 6-13. The virus overwintered in the black-tailed leafhopper. The black-tailed leafhopper overwintered in the form of a nymph and moved back to the rice field in the next spring. After the early rice harvest, it moved to the late rice. After the late rice harvest, it moved to 38 Gramineae plants such as Kanmai and winter rice to overwinter. The number of infected worms is the main factor affecting the occurrence of the disease. Rice is more susceptible to disease before tillering stage. Warm winter and spring, summer and autumn drought are conducive to the disease. The rice seedling is tender, the insect source is frequent and the disease is serious.

Control methods (1) select disease-resistant (tolerant) varieties such as International 26 and so on. (2) it should be planted in pieces to prevent leafhoppers from spreading virus on early and late rice and different mature varieties. Early rice harvest early to avoid the migration of insect sources into late rice. Turn your back to late rice during harvest. (3) strengthen management, promote the early emergence of rice seedlings and improve the ability of disease resistance. (4) popularize chemical weeding, eliminate weeds such as Euphorbia angustifolia, and depress the source of overwintering insects. (5) pest control and disease prevention. The first generation of nymphs propagated in rice fields should be controlled in time, and the peak period of black-tailed leafhopper migrating to double-cropping late rice seedling field and Honda should be grasped, and the insect source should be eliminated before virus transmission. You can choose 25% buprofezin wettable powder, per 667m225g or 35% 100ml EC, 25% aldicarb wettable powder 100g, spray 50L of water, once every 3-5 days, even 1-3 times.