向日葵霜霉病发生规律及防治研究

Studies on the Occurrence Law and the Control of Downy Mildew of Sunflower

向日葵霜霉病是山西省植物检疫对象.1986年在忻州地区首次发现.主要分布在忻定盆地向日葵春、夏播混种区.带菌种子、病株残体和病田土是该病的初侵染来源.春播向日葵发病较轻,但其病株产生的孢子囊可成为夏播向日葵的再侵染菌源.在夏播后多雨高湿的年份,向日葵幼苗再侵染很严重,发病率高达80%以上.播种晚,连作或相邻种植病害加重.当前生产用品种均不抗病,己筛选出5个高抗油用型杂交种可供生产试种.用瑞毒霉拌种,防治效果可达94%以上.

Downy mildew of sunflower [Plasmopara halstedii (Farlow) Berl. et de toni] is one of the quarantined plant diseases in Shanxi province. It was found first in Xinzhou in 1968. At present, it was mainly distributed in the spring and summer-sown area of sunflower in Xin-Ding basin. The sources of primary infection over winter are residues of diseased plant, and infected seeds and soil. The infection rate in the spring-sown sunflower fields was much lower than in the summer-sown fields, but the spore case produced by diseased plants in spring served as an important disease source of reinfection for the summer-sown sunflower. In the years with more rainfall or high moisture, reinfection on sunflower seedlings occured seriously, and the diseased plant rate came up to over 80%.Disease intensity increased with later, repeated or border sowings. The sunflower cultivars used for production now are all susceptible to disease. Fortunately, five high resistant hybrids of oil form have been screened out and supplied for test in production. The seed dressed with Ridomil WP (0.5g a. i./kg) , the control effect reached over 94%.