小麦赤霉病流行预测初步研究

对1952—1963年病害流行程度与穗期气象要素之間的相关性测定結果表明,各年发病程度与4月下旬至5月下旬(小麦抽穗至糊熟)特別是5月上中旬(小麦开花至灌浆初期)的降雨日数、相对湿度呈明显的正相关;与同期的降雨量、平均气温相关不显著。稻桩上产生的子囊壳是本地区初侵染的主要来源,初侵染的数量和流行程度有关,其数量积累决定于雨湿条件。小麦开花灌浆初期最易感病,此时期降雨日数是病害流行的决定性因素。根据十二年資料分析結果,病害流行可以分为六种类型:早期发生型;中期发生型;后期发生型;少雨限制型;低温限制型;生育提早限制型。根据1957—1963年預测圃小麦开花后二旬內的降雨日数与发病率的相关,以发病率为应变量求出迴归方程式:Y=6.61 X—48.35,为中期預測提出雨日指标。

A PRELIMINARY STUDY ON THE FORECASTING OF EPIPHYTOTICS OF HEADBLIGHT OF WHEAT

Headblight of wheatGibberella zeae (Schw.) Petch] is one of the serious wheat diseases in Yangtze Valley. Studies on this disease were carried out in 1952-1963 at Wangting, Kiangsu Province. The results obtained are summarized as follows:The correlation between the climate factors and degree of disease incidence was analysed on the basis of twelve years'' records. It seems obvious that the number of rainy days occured during the period from the end of April to the end of May, especially in the first part of May, is a decisive factor for the epiphytotics of the disease. Temperature, although influencing, is not a decisive factor in the epiphytotics. Observations revealed that the ascocarp on the rice stub is the main source of pathogen of the disease in this region. The multiplication and dissemination of the pathogen depend on the amount of rainfall. Based upon an analysis of the twelve years'' records, the may be there are six types of disease development to be observed, namely, early-period prevalence, middle-period prevalence, late-period prevalence, incidence being checked by scanty, rainfall by low temperature, and escaping from the disease owing to early heading of wheat. Regression method was used to estimate the effect of rainfall on the epidemic in terms of the percentages of headblight and the number of rainy days during the period from the beginning of flowering to 20 days there after. A regression equation was formulated:Y=6.61x-48.35, where Y=incidence of the disease, and X=number of rainy days. These informations may be utilized in forecasting.