Maize dwarf mosaic disease (MDMV), also known as dwarf mosaic disease, mosaic streak disease, sorghum red leaf disease (SRLV), is the world is also one of the major diseases of corn in China. China to North China, Southwest and Northwest China local damage is heavier, the general loss of 3% to 10%. Host range is wide, in addition to the damage to corn, but also for sorghum, corn, millet and other crops and a variety of grass weeds.
Symptoms
Initially in the seedling heart leaf base between the fine veins appeared many oval faded green dots, arranged into one to more intermittent dotted line, later developed into a solid line. The disease continues to expand, in the thick veins to form many yellow stripes, not limited by the thick veins, for the irregular expansion, and the healthy part of the formation of foliage symptoms. The disease continues to expand, forming many round green spots of different sizes, turning yellow, brown, purple or drying out. When the climate is unfavorable to the pathogen, it shows faded green stripes, so it is called foliar stripes. The bracts, leaf sheaths and staminate flowers of severely diseased plants sometimes show green spots, and the plants are short, unable to spike, late spiking or not bearing fruit. In sorghum, it shows symptoms such as phloem, red leaves, red streaks, dwarfing, withered heart, and localized necrosis (Color Plate V, 24, 25).
Pathogen
Maize dwarf mosaic virus (MDMV) is an irregular, long rod-shaped particle with an average length of 653.67 nanometers and a diameter of 17.3 nanometers. The lethal temperature is 55～60℃, the in vitro retention period is 24～72 hours, and the incubation period is 3～10 days or longer. The strains are complex and can be categorized into MDMV-A, MDMV-B and MDMV-O3 strains.
The disease can be spread by rubbing inoculation with disease sap or by inoculation with aphids. Aphids are the only natural vector of the disease. Aphids can travel long distances on air currents. The aphids are stronger than the wheat aphid, corn aphid, and the grass constrictor aphid.
Pathogenesis
The pathogen overwinters on perennial grass weeds. In recent years, it has been reported that virulent seeds are also one of the sources of initial infestation of the disease. Aphids feed on seedlings grown from disease-carrying weeds and poisonous seeds, which carry the virus, and then feed on healthy seedlings, that is, the virus is transmitted to corn or other hosts. As the aphid population grows and migrates, the disease spreads and spreads in the field, resulting in multiple infestations that can easily cause extensive damage to corn. Disease endemic areas due to weeds and seeds with high virulence rate, as long as there is an onset of environmental conditions coupled with large-scale planting of susceptible varieties, it is very easy to make the disease epidemic. 1995, some places planted tuck 107, M017, 8112, 7922 and other self-intercropping lines or to these susceptible self-intercropping lines bred maize hybrids, the results of the field morbidity rate of up to 90% or more, resulting in a devastating loss. When the temperature reaches 20 ~ 25 ℃, is conducive to aphid migration and transmission activities, such as aphids with a high rate of toxicity, the field source of toxicity and more, is conducive to the prevalence of the disease; when the temperature reaches 26 ~ 29 ℃, there is an inhibitory effect of the disease; a longer period of rainfall on the aphid migration, transmission of toxicity is not conducive.
Methods of prevention and control
(1) Plant disease-resistant varieties.
(2) Strengthen cultivation management. Early sowing and transplanting, can avoid the disease and increase production; wheat row spot sowing, seedling transplanting, disease prevention effect is good; timely plowing and weeding, cultivating soil moisture, timely irrigation, increase the application of nitrogen, phosphorus, potassium fertilizer, to promote the growth of maize development is good, to improve the effect of disease resistance.
(3) Prevention and control of aphid transmission. The use of three nine eleven or with furadan seed coating agent seed mixing, seedling application of drugs for aphids.
(4) Remove weeds. Reduce the pathogen.