It wasn’t long ago various brassica growing areas of the country were facing massive insect resistance pressure before the arrival of new insecticide technologies, and it’s a reminder to be careful with latest management programs into the future.

The Lockyer Valley in Queensland and south east Australia were two hotspots for the resistance and agronomists Greg Teske, Queensland and Sigurd Howard, Victoria, are both well qualified to comment on insect management trends in the respective regions. 

Mr Teske of Elders Gatton, has supported Lockyer Valley growers, including some who grow brassica crops in the cooler Darling Downs area, south-west of Toowoomba, during summer, for more than 25 years. 

Mr Howard has provided agronomy support to growers through south east Victoria, as well as in the Werribee and Greater Melbourne regions, during two stints with Nutrien over about 15 years.

The major crops grown in the Queensland region include broccoli, broccolini, cauliflower and red and green cabbages, while in the Victorian areas, cauliflower, broccoli and cabbage are mainly grown, in addition to iceberg lettuce.

Diamondback moth (DBM) has been the key pest in both states, as well as heliothis and cabbage white butterfly, while centre grub, cabbage cluster caterpillar and cluster caterpillar also have been prominent in Queensland.

Both agronomists said overuse of Group 28 chemistry and lack of rotation with other chemistry groups caused the concerning insecticide resistance levels. 

“Chlorantraniliprole was used as a plant hole drench or treatment for seedlings and had a claim to persist for 40 days, but of course it gets weaker towards the end, and then flubendiamide or additional chlorantraniliprole was used,” Mr Teske said.

Both said, fortunately, Plemax insecticide arrived in time, proving to be a pivotal turning point for insecticide resistance management throughout the areas and a powerful rotational option with other alternative options now available.

Developed by ADAMA Australia, Plemax introduced a new insecticide mode of action, novaluron (Group 15), in combination with the trusted strength of indoxacarb (Group 22A), for use in brassica as well as leafy and fruiting vegetable crops.

“I was involved with the early trials of Plemax and the control was outstanding compared with that from other standard insecticides at the time,” Mr Teske said.

“Indoxacarb is still far better than some biological insecticides because it lasts longer, and the novaluron does not exist in other chemistry being used. Indoxacarb is weaker on insects like cabbage cluster caterpillar after some strong use of the single insecticide, but the novaluron in Plemax targets them, so we have a broad range of pests we can control.”

Mr Howard said in rotation with spinosad insecticide, several biological products and, more recently, isocycloseram insecticide, Plemax had certainly become the proverbial another tool in the shed for growers.

“The novaluron really brings uniqueness to it and we know the indoxacarb helps. Plemax has had a great fit in programs because it mixes up the (chemistry) groups. It completely steps away from what we have been doing and has helped to better control insect pest populations and produce a better end product with less physical damage,” he said.

Both say applications of Plemax at early crop stages is ideal.

“When you get the timing right just prior to eggs hatching, you generally won’t have an escape. And if you are late, perhaps due to rain, you still put Plemax on and the novaluron will pick up the larvae. Having the novaluron with the indoxacarb is like having insurance,” Mr Teske said.

“My motto has been to apply early for best results and most growers now understand this. If you go early, and when Plemax has its best fit, you get in front of the pest, control them early and you don’t have too many issues further forward. If you see the eggs are going to hatch in three days, spray in two days’ time.

“It’s all about monitoring to use the insecticide effectively. We have got brilliant chemistry now and if we don’t abuse it, we will have it for a lifetime.”

Mr Howard said particularly in cabbage and cauliflower, the ideal time to apply Plemax was at the early wrapper leaf stage, ensuring the insecticide could get down into the plants before they closed.

“We aim for early control and to stop the egg laying inside the cabbage and lettuce, and to target the caterpillars at an early stage.”

He said with the insect resistance levels and general control now improved, it was important to continue using latest products carefully, and particularly considering the recent expiry of some insecticide patents.

“Rotation, rotation is what it is all about. For the longevity of control, we are also looking forward to more new products coming along that we can rely on,” Sigurd said.

In a special promotion from ADAMA Australia, growers can receive giveaways with purchases of Plemax between September 15 and December 31, 2024. Purchases of 4 litres of Plemax come with a Camelbak 1L Drink Bottle, while 10L purchases receive a 65L EvaKool Esky.

 The company is running a similar campaign with its popular Trivor insecticide. During the same period, purchases of 15L of Trivor earn a Camelbak Drink Bottle, while 40L purchases attract the EvaKool Esky.

*Gift to be redeemed. T&C’s apply. 

To find out more about Plemax and this promotion visit ADAMA.com