Publication Date

1989

Description

Sitona weevils are pests of various legumes throughout the world. In the United States, the clover root curculio, S. hispi­dulus (F.) is the major species associated with lucerne (alfalfa) Medicago sativa L. This insect has until recently remained obscure as a pest of this major forage crop. However, a recent trend in premature decline of alfalfa has prompted further investigation of this insect/legume interaction. Godfrey and Yeargan (1987) and Hill et al. (1969) indicated that S. hispi­dulus reduced alfalfa production. While adults S. hispidulus feeding on the foliage is of little consequence, it is the associ­ation of larvae with the rhizosphere wherein the major stress by this insect is manifest. Larvae can cause considerable damage to alfalfa nodules, as well as to the fibrous, lateral, and tap roots (Quinn and Hower, 1986; Tan, 1988). Indirect damage by S. hispidulus has been suggested in association with root dis­eases of alfalfa and clovers. It has also been suggested that this insect contributes to stand decline of alfalfa and clovers (Tri­folium repens L.) (Underhill et al., 1955; Newton and Graham, 1960). Previous research indentified S. hispidulus in association with decreased yield and quality of alfalfa (Godfrey et al., 1987). The research reported here examined the effect of sustained feeding by S. hispidulus on the ability of damaged plants to fix nitrogen and the impact of this insect on alfalfa productivity and stand longevity.

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Sitona hispidulus Larvaw as a Stress on Alfalfa Production

Sitona weevils are pests of various legumes throughout the world. In the United States, the clover root curculio, S. hispi­dulus (F.) is the major species associated with lucerne (alfalfa) Medicago sativa L. This insect has until recently remained obscure as a pest of this major forage crop. However, a recent trend in premature decline of alfalfa has prompted further investigation of this insect/legume interaction. Godfrey and Yeargan (1987) and Hill et al. (1969) indicated that S. hispi­dulus reduced alfalfa production. While adults S. hispidulus feeding on the foliage is of little consequence, it is the associ­ation of larvae with the rhizosphere wherein the major stress by this insect is manifest. Larvae can cause considerable damage to alfalfa nodules, as well as to the fibrous, lateral, and tap roots (Quinn and Hower, 1986; Tan, 1988). Indirect damage by S. hispidulus has been suggested in association with root dis­eases of alfalfa and clovers. It has also been suggested that this insect contributes to stand decline of alfalfa and clovers (Tri­folium repens L.) (Underhill et al., 1955; Newton and Graham, 1960). Previous research indentified S. hispidulus in association with decreased yield and quality of alfalfa (Godfrey et al., 1987). The research reported here examined the effect of sustained feeding by S. hispidulus on the ability of damaged plants to fix nitrogen and the impact of this insect on alfalfa productivity and stand longevity.