Chemical control of sitona weevil on lucerne

The production and utilization of lucerne in New Zealand

“…The adult weevils emerge in the December/ January period in New Zealand and high populations can considerably damage lucerne stands, and at times completely defoliate them before their flights to oversummering sites (Greenup, 1967;Allen, 1969;Goldson c/a/., 1985). Control of the surface-living adults can be achieved with a number of broad spectrum insecticides at relatively low rates of application (Trought and Stringer, 1976); this is particularly useful in the autumn (i.e., late May) prior to the onset of winter reproductive activity and consequent larval establishment (Frampton, 1984). Mob stocking of lucerne in winter with sheep (500 sheep ha -') reduced resultant spring larval populations of Sitona but because of the severity of the treatment needed to obtain significant reductions the technique is probably of little value as a control measure (Goldson and Wynn-Wilhams, 1984).…”

The effect ofSitona discoideusGyllenhal (Coleoptera: Curculionidae) on lucerne yields in New Zealand

“…Such diverse opinion has probably been accentuated by the fact that the effects of denodulation and root hair depletion by larvae in lucerne (Goldson et al, 1984) may produce symptoms similar to those of other disorders, including poor rhizobial establishment, poor nutrient status, disease, etc. Conversely, there is less ambiguity in the interpretation of the losses caused by defoliation by adults as these effects are easily recognized, and the exclusion of weevils with contact insecticides is relatively simple (Trought & Stringer, 1976).…”