Returns from manuka beetle battle show importance of pest management

Manuka beetle

Success in tackling a destructive beetle on the West Coast of the South Island has underlined the importance of having integrated pest management plans on farms.

Richard Townsend, Research Associate at AgResearch at Lincoln, said that the work in battling the manuka beetle has seen a reduction in pesticide costs as a proportion of milk solid revenues from 23% to 7% a year.

Return on investment over the three-year project has been $10 for every dollar invested.

Manuka beetles (Pyronota festiva and P. setosa) have become a serious and persistent pest on recently developed land on the West Coast. High larval populations in pastures cause loss of seasonal production and deterioration of the pasture sward.

The project was initially launched with support from Landcorp, and was aimed at mitigating the problems caused by manuka beetle attacking pastures that had been developed by flipping the pakihi soils. The Landcorp investment also attracted funding from the Ministry for Primary Industries’ Sustainable Farming Fund and the Ministry of Business Innovation and Employment’s Ecosystems Bioprotection programme, and now involves a community of similarly affected local private farmers.

“The manuka beetle has a sporadic history as a pasture pest, being recorded occasionally damaging pastures on newly developed marginal land. Insecticides are hard to use effectively, and they do not appear to keep up with its relatively high reproductive rate,” says Mr Townsend.

“In this particular region, the flipping of soil to improve pastures has exposed sandy soils, which appears to be a perfect habitat for manuka beetle larvae.

“Most of the success in this project came from understanding the relationship between pest life cycles and soil type. Farmers were encouraged to locate paddocks and areas within paddocks to identify damage prone soil types. This enabled farmers to better target their insecticide applications and reduce its usage by a considerable amount.

“Through our studies of the biology and lifecycle of the two Pyronota species we found out that it would be economically impractical to try and control the adult beetles or eggs and that the larvae (grub) life-stages were susceptible to insecticides.”

One of the initial challenges for the project was helping people identify that they had a problem with manuka beetle in the first place.

“Many of the farmers in the community group were unaware that they were dealing with manuka beetle, thinking the damage was being caused by grass grub,” says Mr Townsend.

“Farmers in the area are now aware that if they are going to use ryegrass and clover in paddocks on the most damage-prone soil types that there will be ongoing issues with manuka beetle.

“We’re now also looking at integrated pest management strategies, such as modifying pasture establishment practices or planting tall fescue or chicory pastures that will hopefully reduce the impact of the beetle.”