Initial Studies On Key Links Of Epidemic Process And Control Technique Of Maize Leaf Spots Caused By Curvularia Lunata

Maize (Zea mays Li) leaf spots caused by Curvularia lunata (Wakker) Boad. happens in Jilin province.The spore can germinate directly in pure water or not. Microdiode and compound in the leaf of maize can accelerate remarkably spores to germinate. The germinated spore will lose infection capacity if they dry more than 30 seconds. They can infect the leaf of maize from 15.0癈 to 35.0癈.But the optimum temperature is 25.0癈. The spore can't infect leaf of maize until the dew time is over 7 hours.The incubation period of the disease is 4-5 days under natural condition, and there is little difference among varieties. The growth stage of maize has little effect on incubation period. Symptomatic appearance will last 8 days. Temperature has obvious effect on incubation period. The size of lesion changes with variety of maize. The least is 0.9mm.the biggest 2.75mm.There are several factors influencing spore production capacity of the lesion. The first is quantity of water penetrating into leaf. The second is whether there is water on lesion. If there is much water penetrating into leaf, the lesion and green part or dead part can produce many spores when RH is 81.5%~85%. If there is no water penetrating into leaf, the lesion may produce spores when having water on lesion and RH is around 100%, otherwise, they only produce few spores even if RH is around 100%. The number of spore produced by juvile lesion (7-9 days) is the same as that by old lesion (twenty days). Lesion can produce spores under either direct light or distributed light. Nitrogenous fertilizer can suppress lesion from producing spores, but increase the number of lesion. Phosphate and potassium fertilizer can accelerate lesion to produce spore, but reduce the number of lesion. The effect of mixed fertilizer (including nitrogenous and phosphate fertilizer) is the same?as that of nitrogenous fertilizer. The number of spore produced is related to the growth stage of maize, but not to the size of lesion.The most of maize varieties in Jilin province are susceptible to the disease. But some varieties are lightly susceptible. The number of lesion and the susceptibility are influenced by growth stage of maize.The spores scatter mostly in the evening and the distance of the disease is more than 53m. The spores on maize residue in field can survive in winter and is the preliminaryinfection source in spring. The distribution model is random.Several effective pesticides were chosen out such as Procvmidone, Mancozeb, Thiram+Ziram, Thiophanate-methyl through experiments. According to the results, integrated control measure was put forward.