吕梁山区粟灰螟的地理分布发生特点及防治意见

吕梁山区海拔高度悬殊较大,形成垂直气候带。粟灰螟(Chilo infuscatellusSnellen)的垂直分布也随海拔高低有轻重之分,即在1300米以下,螟害率随着海拔高度的升高而增加;反之,在1300米以上,随着海拔高度的升高而降低。据1980年和1981年在离石县调查结果计算,海拔高度与螟害率呈极显著的差异。据此可将粟灰螟生境区分为低适生区、最适生区和高适生区。又据损失估计和经济允许水平,将防治区划为:必治区、挑治区和不治区。由于吕梁山区春旱时间长,谷子播种期晚,越冬幼虫迟迟不化蛹,直到6月中旬,总积温达1500℃左右,才开始化蛹,较大降水,有利于化蛹、羽化。此点可作为测报的依据,粟灰螟在吕梁山区一年只发生一代,它的产卵场所特殊,隐害株数量大,根据以上发生特点,提出了针对性的防治意见。

THE GEOGRAPHICAL DISTRIBUTION AND CONTROL OF MILLET BORER,CHILO INFUSCATELLA (SNELLEN) IN LULIANG MOUNTAINOUS REGION

The altitude of the Luliang mountainous region ranges from 700 to more than 1400m.It was found that damage done to the millet by the millet borer,Chilo infuscatella,changed with the altitude,being severest in the range from 1 100 to 1 300 m.Above 1 500m,no incidence was observed. There was only one generation of the borer annually.Winter ispassed almost exclusively in the millet stubble as mature larvae in cocoons.If there is dry June,the overwintering larvae cannot readily pupate and incidence will be less severe.When the precipitation reached 20mm in mid-June (which is quite unusual),the larvae would pupate promptly and injury to millet would be severe that very year. Based on the estimated loss and economic threshold,it would not take much pain to decide if a millet field needs chemical control.