温度对窖藏大白菜主要真菌分离物侵染的影响

在０，５，１０℃下人工接种８种大白菜贮藏期主要真菌分离物。结果有５种可在１０℃的条件下侵染大白菜。其中甘蓝链格孢、希金斯刺盘孢及灰葡萄孢可在０～５℃下产孢。而芸薹链格孢、萝卜链格孢则仅在１０℃条件下可以产孢。鉴于管理正常的传统型及强制通风型大白菜窖的窖温一般不超过５℃，故带入窖中的芸薹链格孢及萝卜链格孢可侵染白菜而不能产孢。因此在北京郊区引起大白菜烂窖的黑斑病的发生程度，主要决定于田间携入病菌量的多少。希金斯刺盘孢、甘蓝链格孢、灰葡萄孢在０℃下能产孢，因此，这几种菌的菌量在上述两种窖中仍可增加。田间携入量与病害在窖中的发生程度关系较上述两种菌要小。控制窖温对抑制这些病菌在窖中的蔓延有着重要的意义。     

Toxicity and protectant potential of camphor,a major component of essential oil of Ocimum kilimandscharicum,against four stored product beetles

The biological activity of camphor, a major component of essential oil of the basil shrub, Ocimum kilimandscharicum, against the beetles, Sitophilus granarius, S. zeamais, Tribolium castaneum and Prostephanus truncatus, was investigated in the laboratory using contact toxicity, grain treatment and repellency assays. Camphor applied either topically, impregnated on filter papers or whole wheat and maize grains was highly toxic to all the four species. Beetle mortality was dosage-dependent with the highest doses of 100 mg/ filter paper and 100 mug/insect evoking over 93% and 100% mortalities, respectively, in S. granarius, S. zeamais and P. truncatus after 24 h exposure. Similar doses induced 70% and 100% mortality in T. castaneum. Camphor impregnated on the grain surface was more effective than on filter paper. There was, however, highly significant reduction in toxicity in grain after only 24 h following treatment. Development of eggs and immature stages within grain kernels, as well as progeny emergence, was completely inhibited in camphor-treated grain. Camphor was also highly repellent to the beetles with overall repellency in the range of 80 - 100%. The potential use of suitable products derived from O. kilimandscharicum as supplementary or alternative grain protectants against insect damage in traditional grain storage in developing countries is discussed.