调查掌握小麦田杂草种类、分布和危害程度，可为筛选高效除草药剂提供科学依据。对定西市不同区域的小麦田杂草发生情况开展了调查，结果表明，定西市共有麦田杂草15科38种，其中单子叶杂草6种，双子叶杂草32种。安定区、通渭县、陇西县、临洮县以及渭源县北部等干旱半干旱区分布较多的杂草有12种，渭源县南部以及漳县、岷县等二阴区分布较多的杂草有13种。有8个杂草优势种，其中苦苣菜、藜、狗尾草、灰绿藜、菊叶香藜等5种杂草危害较重，危害等级达到Ⅲ级；苦苣菜、藜、狗尾草为绝对优势种，危害最重。杂草优势种是防除的重点对象，建议结合杂草特性，筛选高效除草剂加以科学防除。

Studying the weed's species, distribution and hazard degree could provide scientific basis for screening efficient herbicides in wheat fields. In this paper, a survey was conducted on the jeopardizing status of weed in wheat fields of different regions in Dingxi City. The results showed that there were 38 species belonging to 15 families detected in Dingxi wheat growing region, 6 monocotyledonous and 32 dicotyledonous plants, respectively. Twelve species were commonly distributed in the arid and semi-arid regions from Anding distract, Tongwei, Longxi, Lintao and the north of Weiyuan, while thirteen species were commonly distributed in cold and high humidity areas, such as the south of Weiyuan, Zhang County and Min County. Eight dominant species were identified. Five out of them, hazard level of Sonchus oleraceus L, Chenopodium album Linn, Setaria viridis(L.) Beauv, Chenopodium glaucum Linn, Chenopodium foetidum Schrad reached to the grade III, which of Sonchus oleraceus L, Chenopodium album Linn and Setaria viridis(L.)Beauv were more serious than that of Chenopodium glaucum Linn and Chenopodium foetidum. Dominant species are key objectives for prevention and control of weeds. Corresponding herbicides should be selected according to the weed characteristics to improve prevention efficiency.

S451.0