|scientific name Sitona flavescens |
Wherever Trifolium repens, T. pretense and other legumes are found (Campbell et al. 1989).
Migration occurs in spring, with peak activity in April/May and September (Culik and Weaver 1994).
Has no setae. Lower third of rostrum is shallowly bisulcate. Has a distinct, weakly elevated, longutidual carnia that blends into the frontal groove. Eyes are convex. Pronotum is widest in the middle, sides are arcuate, anterior constriction line is not evident. Anterior constriction line on the ventral surface is evident about halfway between the coxae and the anterior of the prosternum. Sides of elytra are arcuate. Discal interstriae are 5 to 6 times wider than the striae. Vestiture of elytra has many flat, recumbent scales that are intermixed sparsely with very narrow scales. Most scales are golden or reddish. (Adapted from Bright 1994, Bright and Bouchard 2008).
Both adult weevils and eggs are able to overwinter (Davidson and Lyon 1979, Campbell et al. 1989). Eggs deposited in the spring have an incubation period of one week, depending on ambient conditions (Davidson and Lyon 1979, Campbell et al. 1989). Larvae consume the root nodules at early instars and the root tissue, including the tap root at later instars (Davidson and Lyon 1979). New generation adults emerge in June and July and feed on green legume foliage, leaving crescent shaped feeding notches on leaf margins (Davidson and Lyon 1979, Campbell et al. 1989). The life span, on average, is one year (Davidson and Lyon 1979, Campbell et al. 1989).
Abundance of this pest species is variable over time and space (Campbell et al. 1989).
In North America and Europe, larvae and adults of this weevil arre commonly found on a number of legume species, including clover species and alfalfa (Murray and Clements 1994, Murray and Clements 1995). Adults feed on the edges of leaves while larvae feed in and on root nodules and roots, and girdling has been recorded (Davidson and Lyon 1979, Campbell et al. 1989).
This weevil has been reported in the southern regions of all Canadian provinces, generally south of 50° latitude (Bright and Bouchard 2008). It also occurs in most of the United States, including California, New Mexico and North Carolina (Davidson and Lyon 1979, Bright and Bouchard 2008). It is believed to have been introduced from Europe, where it is widespread (Campbell et al. 1989).
The name Sitona flavescens is the accepted name for this species in North America, although it is also known as Sitona lepidus Gyllenhal, especially in literature from Europe (Bright 1994, Bright and Bouchard 2008). Larvae are believed to weaken the immune defenses of clover and alfalfa roots, which leads to secondary infections, including root rot and bacterial wilt (Davidson and Lyon 1979, Campbell et al. 1989). Damage to roots also leads to wilting and plant death in dry conditions (Campbell et al. 1989).
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