Help sought for biological control

Press, 13 June 1986, Page 10

Help sought for biological control

A five-year plan to rid lakes and farmland of noxious weeds, using biological control, has been proposed by scientists at the Entomology Division of the D.S.I.R. in Auckland. The leader of the division’s agriculture group, Dr Oliver Sutherland, is asking for funds for the proposal from the Noxious Plants Council and from district noxious plant authorities throughout the country. He made the request at the recent conference of the Institute of Noxious Plant Officers in Wanganui. Dr Sutherland said, in his group’s most recent biological control project, a small South American beetle was successfully wiping out alligator weed in Northland lakes.

The group has recently started another biological control programme to control ragwort in parts of the North Island. “To date, we have had a completely successful overwintering of the ragwort flea beetle,” he said. “The beetles have survived and are reproducing at every release site.”

The new proposal is for all 95 noxious plant authorities in New Zealand, and the national

council, together with the D.5.1.R., to jointly fund the work to control five major weeds — ragwort, nodding thistle, Californian thistle, gorse and broom.

The district authorities are being asked to inject $2OOO a year, for five years, and the national body is being asked to subsidise this amount. “The aim is to boost farm production by using an economic method of controlling weeds, at no direct cost to individual farmers,” said Dr Sutherland.

Dr Sutherland says biological control programmes involve two stages, research and applied. The research involves searching overseas for a suitable control agent, exhaustive safety testing, quarantine and further testing in New Zealand. He said it was appropriate for the D.S.I.R. to fund this part. The applied stage involves rearing the insects, releasing them into the field and evaluating their success rate.

The funding from a national plan was needed to employ two technicians, one at Auckland and one at Lincoln, to rear and release large

numbers of the new agents for the five weeds.

"This is labour intensive,” he said. “Without it, the project would be slowed down considerably and would take years longer.”

A nationally funded project would speed up the programme by five to 10 years, to the direct benefit of farming and the community.

Dr Sutherland said if the national plan went ahead, but some authorities were, however, not willing to join in, "obviously, releases of control agents would be made in those areas which had contributed to it.”

Dr Sutherland pointed out it was not possible to guarantee 100 per cent success for any weed control programme, whether biological, or chemical using herbicides.

“But the insects we release are the ones which have often been successful in other countries.” The scientists have new insects ready to be mass reared and distributed for the control of ragwort, nodding thistle and broom. Control agents for gorse, Californian thistle, and possibly some other weeds, would be included later in the five year plan.