Thistle beetles sighted , a good sign

Thistle beetles released last year for a biocontrol programme have been sighted this summer, which programme directors say is a promising sign reports the Southland Times. The programme involves the Californian thistle Action Group and Landcare Research, largely in South Otago and Southland, through the MAF Sustainable Farming Fund. Thistle beetles (cassida rubiginosa) were released last summer and autumn have been sighted again this summer. The beetles overwinter in the leaf litter and begin a new life cycle when the Californian thistles emerge again in the summer. Clutha Agricultural Development Board and Action Group projects manager Malcolm Deverson said reports that the thistle beetles themselves and evidence of their feeding had been seen at most of last year's seven release sites in South Otago and Southland. "They create transparent `windows' in the leaves that are easy to distinguish from other leaf damage," he said."It's really exciting and unexpected to see so much evidence of the insect's establishment so early. Often these biocontrol agents that get released are difficult to find. Only 50 or 100 are released at a time and it can be four or five years or more before they are seen again." The Californian Thistle Action Group made a NZ first release of these thistle beetles at Waitahuna West near Lawrence November 2007. Farmers were unlikely to find huge patches of damaged thistles until beetle numbers built up.