Rate of dispersal a key success factor for weed biological control agentswithin forest plantations

摘要

Buddleja davidii (buddleia) is an invasive weed of botli natural and plantation forests in New Zealand. The weed has been estimated to cost the New Zealand plantation forest industry up to 2.9dollar million annually in chemical control costs and lostproduction. The buddleia leaf weevil, Cleopus japonicus, was released in New Zealand in 2006 as a biological control agent for this weed. If C. japonicus can reduce the growth rate of B. davidii in the first three years after clearing of land for planting it has the potential to reduce the need for chemical control of this weed. To determine the effectiveness of this control agent, B. davidii seedlings were planted in an insecticide exclusion trial and the dispersal of C. japonicus and feeding damage on plants was monitored according to distance from a single source population. Cleopus japonicus dispersed at a rate of approximately 100 m per annum. There was a strong correlation between larval numbers per plant and percentage defoliation. A significant reduction in B. davidii height in untreated compared to insecticide-treated plants only became apparent 436 days after trial initiation.