Study On Black Spot Disease Of Liriodendron Spp

Leaf black spot was a new disease found on Liriodendron spp.. The disease caused black spot, made leaf losing green and falling earlier, stunt tree growth and lowered show value. In this paper, the disease pathogens, invasion cycle and control ways were studied.According to the tissue isolation and identification result of the pathogens, the pathogens that caused black spot disease were Colletotrichum sp. and Alternaria sp.. The disease occurred on leaves in middle of April and developed in May and June. It was the most serious period in July and August. The disease stopped developing and the diseased leaf began to fall down in middle of June. The earliest species of falling leaf was Liriodendron tulipifera and the last was Liriodendron chinense.Colletotrichum sp. and Alternaria sp. all could infect directly or indirectly by wound. The direct infecting capacity of Alternaria sp. was higher than that of Colletotrichum sp. and the infecting capacity by wound of Colletotrichum sp. was higher than that of Alternaria sp.. During the developing process of disease, two pathogens were found in both healthy twigs and leaves while mainly persisting in the twigs. This showed two pathogens of the disease have latent infection on Liriodendron spp..In different developing stage of the disease, two pathogens had different quantity and effects. The pathogen in pathological tissue in April was mainly Alternaria sp. and with developing of the disease, Colletotrichum sp. would gradually take the place of Alternaria sp. after May and became major pathogen in the pathological tissue.The two pathogens could be found in winter buds, twigs and diseased tissues in effoliation with hyphae in winter. The quantity of two pathogens in twigs and effoliations was obviously much more than that in winter buds. The original infection pathogen was mainly in twigs.The severity of black spot disease was related to species of Liriodendron spp. and the quantity of Colletotrichum sp.. As far as the big tree was concerned, the most serious disease among Liriodendron spp. was L. tulipifera. The next was L. chinense. The severity of disease was positively correlated with the quantity of Colletotrichum sp., that is, the disease became serious with the increasing quantityof Colletotrichum sp.Based on the toxicity of fungicides tested in the lab, It showed that, among ten fungicides, Chlorothalonil(Dacohtech, Daconil2787) and Prochloraz had high inhibition to the hyphae of Colletotrichum sp. and Alternaria sp.. Prochloraz and Baoxianke(mixed with Topsin-M and Thiram) had high inhibition to spore sprouting of Colletotrichum sp. and Alternaria sp.. Although it had good effect for using above fungicides in field experiment, the time using fungicide was very important to control effect. The earlier the fungicide use, the better the control effect was.