CLOVER ROOT WEEVIL FEEDING AND LARVAL NUMBERS ON WHITE AND RED CLOVER SEEDLINES

Two adjacent field trials were established in pasture to assess the relationship between clover vigour and clover root weevil ( Sitona lepidus; CRW) populations. Trial 1 contained 31 white clover and three red clover seedlines. Trial 2 evaluated nine white clover seedlines selected for field vigour against clover nematodes. All seedlines were visually scored for weevil adult feeding and plant vigour in summer and autumn. In winter, selected seedlines representative of the vigour range across the trials were sampled for CRW larval numbers and root weight. There was a direct relationship between clover vigour in April and the number of CRW larvae establishing on seedlines. A similar relationship was evident for CRW larvae per gram of root in June. The results suggest that high performing clover lines, such as Grasslands Kopu II, were able to maintain productivity in spite of feeding pressure by CRW (tolerance), rather than by the suppression of CRW adults, egg laying or larval numbers (resistance).