Beneficial pests lower insecticide costs

Boggabri cotton and grain farmer and Nuffield Scholar in 2006, Andrew Watson, Kilmarnock, in an address to the Nuffield conference in Tamworth, gave a detailed report on how a project of tree corridors planted by his family to stabilise the banks of the Namoi River has grown and developed insect and microbat populations which is providing him with natural and effective means of pest control.

He said those with regular cotton programs would need to start thinking about their pest control plans and making the most of natural predators and beneficial insects.

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Remnant vegetation is a perfect host for microbats, and he encourages growers to retain older trees and logs as they are home to microbats. He said that some old remnant vegetation has been tested and found to house four times the national average of microbats.

"It's certainly having the understanding that microbats live in remnant vegetation rather than new treelines because it's the older trees with the knots and the hollows and the crevices in the bark is where they live.

"The new, younger tree lines don't. So the idea of leaving old-growth timber and fallen trees in a tree line rather than cleaning them up to plant a new tree line is really important."

Mr Watson also advises growers to pause and consider what an insecticide spay might do when added as an accessory to a herbicide application.

"I always take a breath before we rush in and apply insecticides, is one of the views I've always taken," he said. "We don't want to throw the insecticide in with whatever herbicides we apply. It always doesn't feel right to me because there may not be a need.

"Certainly, we've seen seasons where we've seen a buildup in aphids, for example, in canola.

"And we're seeing some lady beetles around. So the question posed to the agronomist, do you want to spray or do you want to see if the beneficials build up?"

Mr Watson said increasing populations of beneficial insects is a week-by-week process.

He said the decision not to apply a pesticide can often result in a booming ladybird population and no aphids.

"So it's a matter of having a little faith that they will build up," he said.

Farmers who want to get on the front foot by building a population of parasitic wasps should plan to get their orders early. This can be achieved by working with local agronomists to get the orders in and cost-effective delivery of the insects.

"You do have to get those insects bred, and you have to get them delivered promptly," he said.

"Once those wasps are released, they'll breed and continue to produce, populate, and inhabit your farmland and surrounding areas that might grow insects and have a reasonably short lifecycle.

"But the point about what we're trying to do is we're not trying to control the past with the release we do.

"It's the subsequent populations. We're hoping we'll build it, and then five, six, and seven weeks from when we release, the real work is getting done because we'll have had several generations. That's the multiplier effect to control the pests. "

Mr Watson said the impact of beneficial predators on his canola crops has been impressive this year.

"It's the first time we've released in canola, and it has been excellent control of the aphid pests. There are so many parasitised aphid eggs in the canola crops that it will be a great control.

"We weren't sure when we released three different sorts of parasitic wasps, and there's a bit of a study going on to see which one was the most effective. So we could probably hone the delivery onto one particular wasp and make the process slightly cheaper."

Quirindi district's Peter McKenzie is the managing director and head agronomist for Agricultural Consulting and Extension Services.

He said setting up an integrated pest management system on cropping farms needed a "whole of system approach".

Growers of cotton and other crops needed to "go through the hard yards and hold their nerve" regarding insect pest control.

Mr McKenzie said post the drought, the environment, with cooler and damper growing seasons, has supported the growth of beneficial populations of beneficials. "But it's more than just cotton crops; it's about other crops in the area that offer the environment that contributes to the overall population build-up," he said. Mr McKenzie said in the past three weeks, he and his team have been observing aphid populations, and they have been encouraged by resident populations of wasps predating on the sucking pests.