Home > IPM Crop Protection Keeps Pests at Bay, Saves Sprays in Tomato Crops

IPM Crop Protection Keeps Pests at Bay, Saves Sprays in Tomato Crops

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The Eastern Mallee region of Victoria - encompassing the towns of Kerang and Boort - is home to one of the major process tomato growing areas of Australia.

Produce from blocks of 20 hectares or more go into a wide array of foods including tomato sauces, juice and canned tomatoes.

As with most horticultural sectors in recent times, the tomato industry has faced an ever-increasing battle keeping up production while keeping pests at bay.

In the not-too-distant past - up to the mid-1980s in fact- DDT was used as the "kill-all" treatment for "bugs" on tomato plants.

But with DDT being banned in the 1980s, the then Victorian Department of Agriculture, tomato growers and agronomists got together to develop a strategy of integrated pest management (IPM) that would reduce the amount of harmful chemicals being sprayed on crops, yet maintain crop protection.

"Coming up to 1986/87 most growers had just been using DDT. You went and sprayed two or three times with DDT and that was it," said Quambatook Rural Supplies' Michael Hind, a specialist IPM consultant to tomato growers.

"You obviously got reasonable control in the paddock but once DDT was banned growers went on to spray every 10 days or fortnight regardless of whether there was anything there or not, because no-one was looking as closely at the plants.

"We started doing the IPM with the Department of Agriculture back in 1988/89. We had a project which ran in with them up until last year."

A key part of the IPM regime for tomatoes has been regular crop monitoring to determine the impact of parasitic insects in controlling pests such as heliothis.

The degree of parasite infestation found on plants determines the level of "natural" control and indicates the level of insecticide "assistance" needed to keep pest numbers down.

"We basically worked on heliothis and set thresholds on pests such as sap suckers and other lepidopterous species," Michael said.

"We then expanded that to diseases we put a program in place for identifying and treating powdery mildew and bacterial speck."

Michael said IPM regimes were set up for growers at the same time as other agronomic services such as fertiliser programs.

"They sow the crops, and from then on we monitor them on a weekly basis – from emergence through until about two weeks before harvest," he said.

Random samples of 30 petioles are taken to determine the level of parasitism in the helitothis eggs from wasps such as trichogramma or telenomis.

Eggs are collected in trays and inspected 4-6 days later.

If the eggs turn black it means they have been parasitised by the wasp and this enables growers to accurately gauge the level of spraying required for adequate pest control.

"Once you get five eggs hatched in 30 petioles, then that's the spray threshold," Michael said.

He said regular scouting for pest presence let growers and agronomists know if the beneficial insects were doing their job.

"Our job is to go to the paddock and assess whether the crops actually need spraying or not," Michael said.

"So instead of putting out 10 or 12 sprays, we cut them back in the first year to five or six - just by spraying at the right time."

Michael said growers were keen to adopt the IPM regime for two main reasons: saving money and time and reducing the amount of pesticide use.

He said the major produce buyers were becoming more demanding in terms of the way produce was grown and treated.

Resistance to synthetic pyrethroid insecticides has also been an issue in recent times, with a change in the wind direction resulting in the migration of resistant species of heliothis.

"For the past two years we've had north-easterly winds instead of north-westerly winds and instead of getting heliothis puntigera, we've ended up with H. armigera that have come in from the southern Riverina," Michael said.

"Most of the insecticides we had previously been using were based around the synthetic pyrethroid and endosulphan program and the moths that have come through have been synthetic pyrethroid resistant."

According to Michael, this is where Avatar by DuPont will fill the gap and prove a boon for growers.

"That's one of the fits that Avatar will have with the program- there's no known resistance," he said.

"We'll be using a synthetic pyrethroid early and then go on to Avatar.

"It's also going to be softer on our beneficials than some of the insecticides we're currently using."

Michael said he was also impressed with Avatar's residual qualities.

"It has the ability to stick on the plant- with a lot of insecticides you may get a five-to-seven day residual out of them," he said.

"At least with Avatar we're going to get extended residual periods, so if something's coming into the crop and we've used the three sprays on the bush in the main part of the growing season, then we should have reasonable coverage.

And if we get egg lays inside the plant we should be able to pick up some of those caterpillars when they hatch."

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