WA orchards beat rising weevil damage

Oct. 29, 2023 | 5 Min read
Limited chemical control options and high reliance on the Group 22a insecticide, indoxacarb, for control of weevils in pome and stone fruit orchards throughout South West WA always meant a new option would be warmly welcomed.

Limited chemical control options and high reliance on the Group 22a insecticide, indoxacarb, for control of weevils in pome and stone fruit orchards throughout South West WA always meant a new option would be warmly welcomed.

A number of weevil species are pests across most Australian apple production areas, but have a higher impact in WA, Victoria, Tasmania and South Australia, causing damage to fruit and leaves, affecting marketable fruit and tree vigour.

One of the industry’s most familiar faces, Dave Stewart, horticulture specialist with Elders, said the reliance on a single active ingredient for control of such an important pest was a risk to the industry.

As a result, he said the industry needed another control option desperately and when Bayer released Vayego, containing the fast acting and long-lasting Group 28 insecticide, tetraniliprole, its uptake became a “no-brainer’’.

“We really value an alternative like Vayego to support our current control options and to bring a new dimension to weevil control,’’ Mr Stewart said.

Vayego provides breakthrough selective control of various weevil, moth, beetle and fly pest species in pome and stone fruit, as well as almonds and macadamias.

Its systemic action and residual efficacy targets multiple life stages, causing rapid feeding cessation to minimise damage, while, importantly, when used as directed it’s soft on many beneficial species, and offers a short withholding period.

In the Glenoran region, west of Manjimup, Mr Stewart has for many years worked closely with Bec Whittaker, farm manager at the Casotti Group’s Ladycroft Orchard, which, after earlier running into some significant challenges, is experiencing a stark turnaround in weevil control in apples with Vayego.

“We were using indoxacarb previously and we were having to deal with 60 per cent of fruit having some weevil damage – from minor stalk damage to chewings on the fruit,’’ Ms Whittaker said.

“Now we are probably only getting five per cent damage, so it’s a massive improvement and our pack-outs have probably improved 30 per cent.’’

Ladycroft Orchard comprises a range of Pink Lady, Gala, Bravo and Granny Smith apple varieties grown over about 50 hectares, and at the end of this year will become one of the few apple orchards in Australia to plant the new US variety, Cosmic Crisp, a member of the Honey Crisp family, over 17ha.

While the age of its trees ranges from 28 years down to one-year-old, the bulk of the orchard comprises older trees and it has commenced replanting of 4ha annually.

Ms Whittaker said garden weevil and light brown apple moth provided the greatest pest pressure and it was fortunate that Vayego, in addition to controlling weevils, also targeted the moths, whilst woolly aphids and mealy bugs can also create issues.

“As well as damaging the fruit crop, the weevils chew on the trees and damage next year’s buds,’’ she said.

“If there is some damage on small fruit, we have to spend money on re-thinning and then picking is slower as well, to ensure you are not putting damaged fruit in the bin.’’

After becoming aware of Vayego via Mr Stewart, Ladycroft Orchard was one of the first enterprises to use the insecticide when registered and immediately applied it across the orchard due to the weevil pressure.

“After the first spray, we saw a lot of dead weevils and we went back in three weeks later and the population was almost wiped-out,’’ Ms Whittaker said.

“It’s a slow knockdown. You may not see dead weevils for a while, but it stops the chewing and the damage straight away.’’

This year, they applied a cover spray and then only two blocks required a second application of Vayego.

“Two blocks were showing weevil pressure, so we sprayed them, and we haven’t seen any more pressure,’’ Ms Whittaker said.

To help preserve the latest insecticide, Mr Stewart urged growers to undertake insect scouting before applications. Ms Whittaker agreed, saying the days of full cover orchard spraying were over due to the potential risk of resistance it caused.

“We address every block according to insect thresholds. We have bands in the trees that we open, count the weevils and when the numbers are up to 10–15 in a block, we know we will have a problem. If the numbers are high in a block, we will also treat the block next door.’’

She said compared with applying indoxacarb, Vayego also was more friendly to use with various beneficial insects including ladybird beetles, lacewings and Trichogramma sp., which helped to control the woolly aphids. Ladycroft also uses beneficial insects from Bugs for Bugs to predate on pests such as two-spotted mites.

Vayego was applied at the orchard using air-blast sprayers, generally with water rates of 1000 litres/ha to ensure excellent coverage.

Ms Whittaker said while indoxacarb was a little sticky, Vayego was easy to mix.

Categories Resistance management