Investigation of soil insect pest species, damage and resistance in alfalfa

In order to select resistant varieties that can be recommended for use in alfalfa production, resistance of 44 varieties in Hohhot were evaluated, soil insect species were identified, damage of alfalfa roots by soil insects was determined, and percentage of injured plants were investigated in this study. The results showed that soil insect pests in this site were Maladera orientalis, Anomala mongolica, Selatosomus gravidus, Gonocephalum reticulatum and Opatrum subaratum, which accounted for 27.56% of total soil insect number. Insects inflicted plant injury by chewing root cortexes or boring root steles. The damage rate in plants was 1.19 to 28.85% (average 2.77%). All alfalfa varieties were highly resistant based on the National Alfalfa and Forage Alliance (NAFA) in the United States of America. Nevertheless, relative resistance existed between varieties. Based on analysis with a clustering method, the 44 varieties were divided into six groups: 10 varieties (22.64% of total varieties) were high resistance (HR) varieties, including Xinmu No. 2, MF4030, Hunter River and MF4010; 10 were resistance (R) varieties (29.54%), including Zhongcao No. 3, Zhaodong and Magnum; 13 were moderate resistance (M) varieties (22.73%), including Aohan and SK3010; 9 were low resistance (L) varieties (20.45%), including Nongmu 806, Zhungeer and Giant; and 2 were susceptible (S) varieties (4.55%), Rambler and Dryland.