Occurrence And Control Of Red Blight Disease Of Metasequoia

Metasequoia glyptostroboides is an important city greening tree species in china,especiallyin middle and lower reaches of Yangtze River. As the planting area expanding, metasequoiaglyptostroboides diseases and pests get more serious. The growth and yield of metasequoiaglyptostroboides and greening effect have been seriously affected. Red blight disease ofMetasequoia is an important disease with a wide range of occurrence and aggravating trend. Inview of this, the experiment investigated the symptom and occurrence regularity of red blightdisease of metasequoia in Shanghai, determined the pathogens of red blight disease ofMetasequoia, and studied the biological characters of the pathogens. The prevention method toMetasequoia blight has carried on preliminary research. The main results are as follows:Metasequoia blight occurred mainly in the leaves of Metasequoia glyptostroboides, leadthe leaves of Metasequoia glyptostroboides to dry and brown from blade tip, or brown spots inother parts of the blade. There is yellow halo in sickness health junction. In the late stages, thediseased leaf surface produces black dots. Seriously the disease leads to early deciduous. Thedisease appeared in May, when temperature began to rise. With the rise of temperature thedisease aggravated gradually. In July and August, the temperature reached the annual maximum,with increased rainfall, the disease appeared the peak spreading. After September, as thetemperature drops, the disease stopped development. Metasequoia of single row or sporadicdistribution was more sensitive than that with a higher canopy density. The resistance ofMetasequoia that used as street tree was weak, and the disease was more serious than thatplanted in farm. The Metasequoia with a poor growth potential was more likely to be infected,especially the ones used as street trees.The pathogens of Metasequoia blight are Alternaria tenuissima and Pestalotiopsisheterocornis. Two pathogens can grow in the temperature range of10~35℃, the optimumgrowth temperature is28℃。Two pathogens can grow in pH range of4~11, on the growthenvironment of pH adaptability, with good adaptability to pH. Different light treatments hasmarked effects on spores production of P. heterocornis, the spores production of P.heterocornis was significantly less than that of other treatment in cultured under darkconditions. The most favorable carbon for mycelial growth of A. tenuissima was glucose, andmannitol for the myceliar growth of P. heterocornis. The most favorable nitrogen source formyceliar growth of A. tenuissima was glycine, and ammonium nitrate and ammonium sulfatefor for the myceliar growth of P. Heterocornis. With the reduced relative humidity, theconidium germination rate of two pathogens decreased. P. heterocornis was more sensitive torelative humidity, in the relative humidity below85%, the conidium of P. heterocornis stopgerminating.The pathogens overwintered in the fallen leaves by means of conidia and hypha, and theconidia in the fallen leaves were the initial inoculum for new areas. The conidia dispersed by airand rain splashing. The conidia of A. tenuissima dispersed in the mid-April and the number ofconidia increased gradually. P. heterocornis conidia appeared in mid-July when rainfallincreased, and the number of scattering conidia increased in rainy days. The latent period ofstab incubation is much shorter than that of spraying. With the increase of temperature, thelatent period of the pathogens shortened.The best inhibition effect on myceliar growth of A. tenuissima was difenoconazole, withEC500.3892g/ml, followed by mancozeb, with EC508.7644g/ml. The inhibition effect ofcarbendazim on myceliar growth of P. heterocornis was the best, with EC502.3948g/ml,followed by difenoconazole, with EC502.7059g/ml. In the field experiment, the best control effect was dealing with difenoconazole and white carbendazim, when diluted1000times, theInhibition rate reached80%above, followed by thiophanate methyl and procymidone.In the flat antagonist, the inhibition effect of Trichoderma JK-TS5on two pathogens wasthe best, followed by Trichoderma Cfa-82907, the inhibition rate of the two biocontrol fungusto pathogens was above30%. The inhibition rate of onion burke holder bacteria NSM-05to twopathogens was72.6%and84.2%, while JK-007reached59.8%and79.8%. The inhibitioneffect of biocontrol fungus shake culture to pathogens was20~30%, while the inhibition effectof biocontrol bacteria shake culture has a strong inhibition effect to pathogens. Also with thedilution increases, the inhibition effect of culture on spore germination was significantlyattenuated.