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对银杏苗圃中发生苗枯的植株进行病原分离及回接试验,发现引起银杏苗枯的病原为Phytophthorasp.称这种苗枯为银杏疫病。该病危害银杏幼嫩苗木的地上部分,未见危害根部和多年生成林树。叶片受害似开水烫伤状,茎干受害则变黑,黑色病斑环绕茎干一周后,病茎以上部分叶片青枯萎垂。病原菌在PSA培养基上,菌落白色绒毛状,28℃下7d可长出大量孢子囊,易产生厚壁孢子,病菌生长适宜温度为24℃~32℃。人工接种可致受伤银杏叶片及幼嫩茎干严重发病,但无伤茎叶发病较轻或不受害。在田间,该病5月初开始发生,3d~5d病情达到高峰,苗圃的发病率为10%~20%,有明显的发病中心,5月底病情稳定,以后病害不再发生。用含药培养基及含药纸碟法测定,甲霜灵及甲霜灵锰锌对病原菌有很强的抑制作用。病原种鉴定正在进行。
Phytophthora blight was observed in Phytophthora sp. Call this seedling blight gingko blight. The disease endangered ginkgo seedlings of the aboveground parts, no harmful roots and perennial forest trees. Leaf damage like boiling water scalding, stem damage is black, black lesions around the stem a week later, some of the diseased leaves above the withered leaves withered. Pathogenic bacteria in the PSA medium, the colonies white villous, 28 ℃ 7d to grow a large number of sporangia, easy to produce thick-walled spores, the optimum temperature for the growth of bacteria 24 ℃ ~ 32 ℃. Artificial inoculation can cause serious injury of young ginkgo leaves and young stems, but no injury to stems and leaves less or no damage. In the field, the disease began to occur in early May, and the disease peaked from 3d to 5d. The incidence rate of nursery was 10% -20%. There was a clear incidence center and the disease was stable by the end of May. With drug-containing medium and drug-containing paper plate method determination, metalaxyl and metalaxyl manganese zinc has a strong inhibitory effect on pathogens. Pathogen identification is ongoing.