苹果树腐烂病的发病过程和药剂防治研究

本文分两部分。第一部分概述了陕西风县秦岭高地苹果树腐烂病的发生发展过程,指出腐烂病菌主要是先在树皮的落皮层内潜伏侵染,进而侵害健组织。第二部分为防治试验。根据腐烂病的发生发展过程,于6月下旬和11月中旬对主干和大枝下部涂40%福美砷可湿性粉剂50倍悬浮液二次,获得了施药部位新病减少90%,“病疤重犯”减少80%的防治效果。与在辽宁兴城的试验,防效近似。

A PRELIMINARY STUDY ON THE DEVELOPMENT OF VALSA CANKER (VALSA MALI MIYABE ET YAMADA) OF APPLE TREES AND THE METHOD OF CHEMICAL CONTROL

Valsa canker (Valsa mali Miyabe et Yamada) is one of the most destructive diseases of apple trees in North China. Observations on the development of cankers and experiments on the method of chemical control were conducted from 1975 to 1979 in a heavily infected orchard in Feng County, Shansi Province. The causal fungus which had established in the bark initiated its development in rhytidomous tissues, leading to the production of superficial cankers, and invaded the underlying or neighboring healthy bark further when the vigor of apple trees declined. In the period from June to early August, rhytidomes were differentiated in some parts of mature trees. About one month later, superficial cankers were produced as soon as dead rhytidomous tissues being digested. The fungus hyphae in superficial diseased tissues advanced beyond peridermal barriers toward early winter, and, subsequently, the necrosis and collapse of healthy barks occured. In the meanwhile, the fungus colonizing in rhytidomous or other dead tissues on the bark invaded into healthy bark, and local lesions resulted. The canker continued to increase and extend throughout the dormant period of apple trees, with an outbreak in early spring. In April and May, as the growing vigor of trees was resumed, the invading fungus stopped. Based on the knowledge of initiation and development of Valsa canker, an expeimental Program for controling this disease by fungicide application was carried out. Painting the trunk and lower parts of large limos with 2% suspension of 40% asomate w.p. before the appearance of visible symptoms on rhytidomes differentiated in current summer season, with the aim to Prevent the Production of superficial cankers during summer and autumn seasons, and painting in late autumn or early winter again to Prevent the production of new lesions. The number of cankers on treated parts of apple trees was 90% less than that on the corresponding parts of untreated ones. Further investigations are in progress.