Yakabe L E, MacDonald J D
Department of Plant Pathology, University of California, Davis 95616.
Plant Dis. 2010 Mar;94(3):320-324. doi: 10.1094/PDIS-94-3-0320.
Ramorum leaf blight, caused by Phytophthora ramorum, has reemerged at several California nurseries after removal of infested material. In many cases, reemergence was not associated with reintroduction of the pathogen and may be attributed to inoculum surviving in soil beds because P. ramorum propagules can survive for over a year in soil. Using artificially infested soil in microcosms, fumigation and heat treatments were examined as potential eradicants of P. ramorum from soil. Treatments with chloropicrin, Vapam, and iodomethane were effective in reducing P. ramorum propagules below detection limits. Basamid was consistently effective only when fully incorporated into the soil. Application of Basamid (392 kg/ha) at infested ornamental nursery sites mirrored results from microcosm experiments, indicating that a tarp cover over treated soil is necessary for reliable efficacy. Dimethyldisulfide, 1,3-dichloropropene, and two formulations of hydrogen dioxide were less effective, resulting in only partial reduction of propagules. In heat treatments, P. ramorum in soil microcosms remained detectable 42 days after microcosms were incubated at 30 and 22°C but was not detectable in soil heated above 40°C for 3 days. Results from a solarized field plot indicate that prolonged sublethal temperatures, between 35 and 40°C for 42 days, can be effective in eliminating detectable propagules of P. ramorum.
由樟疫霉引起的拉莫伦叶疫病，在清除受侵染材料后，已在加利福尼亚州的几家苗圃再次出现。在许多情况下，疫病再次出现与病原菌的重新引入无关，可能是由于土壤床中存活的接种体，因为樟疫霉繁殖体在土壤中可存活一年以上。在微观世界中使用人工侵染的土壤，研究了熏蒸和热处理作为从土壤中根除樟疫霉的潜在方法。用氯化苦、威百亩和碘甲烷处理可有效将樟疫霉繁殖体减少到检测限以下。棉隆只有完全混入土壤中才始终有效。在受侵染的观赏苗圃场地施用棉隆（392千克/公顷）与微观世界实验结果相符，表明处理过的土壤上覆盖防水油布对于可靠的防治效果是必要的。二甲基二硫、1,3 - 二氯丙烯和两种过氧化氢制剂效果较差，只能部分减少繁殖体。在热处理中，土壤微观世界在30和22°C下培养42天后，樟疫霉仍可检测到，但在40°C以上加热3天的土壤中则检测不到。一个太阳能处理的田间地块的结果表明,在35至40°C之间持续42天的亚致死温度，可有效消除可检测到的樟疫霉繁殖体。
