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Insect control vital for South East grape growers

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About

Category

  • Grower Stories
  • Product News
  • Growers Edge

Date

08 November, 2017

Product

Location

South Australia

Escalating mealybug and scale populations and presented winegrape growers with a real challenge in recent seasons. Read about the range of strategies they have been using to meet this challenge.

Winegrape growers in South Australia’s South East have been adopting a range of strategies to combat problems associated with escalating mealybug and scale populations, but they remain a concern, according to local Landmark Viticulture Agronomist Michael Zerk.

Originally from Naracoorte, Michael has been working in the region for five years mainly from the Padthaway area down to Mount Gambier. Prior to this he worked in the Adelaide Hills, Langhorne Creek and Barossa Valley wine regions for three years based from Landmark’s store at Strathalbyn.

He has seen a number of vineyards with high, and increasing, populations of mealybug and scale, but he said in most cases there were very few control options available.

Varying conditions in recent seasons have also presented challenges for insect control.

“The spring of 2015 was warmer and insects were active early, but, as vines also developed and flowered earlier, we were unable to make two applications of the insecticide, Movento. Last season it was cold and wet, so growers were favouring fungicide applications and insects were slower to present themselves. When we could see that mealybug and scale were active, the withholding threshold (to apply Movento) had been reached,” Michael said.

He said scale had severely affected some vineyards, particularly reducing shoot vigour in cabernet, sauvignon and chardonnay, and mealybug became more apparent in bunches.

“A significant problem with mealybugs and scale are that they exude honeydew, which can induce sooty mould and reduce grape quality. These insects are also the most important vectors for spreading viruses.’’

“Shoot vigour is often reduced when populations are high, which means heightened risk of sunburn, and flavour can be affected.’’

Michael said many vineyards in the region had been established for around 20 years and he noticed the insects and other problems were increasing with age.

“These insects have gone somewhat unnoticed by many people, myself included, but once a threshold is passed, they become a significant problem.’’

“It is important that we look at all aspects of how we manage our vineyards – from canopy architecture to crop treatments – to understand why these species have prospered. We generally find good numbers of beneficial species, but whether these are the right ones for scale and mealybug must be confirmed.’’

He said growers had previously tried using winter oil, although it cannot be used after budburst and there were issues around using high rates for optimum coverage.

Chlorpyrifos has been used prior to budburst and has been highly effective, but some companies prefer that it no longer be used in vineyards. A post-harvest application can be effective, or an early knockdown prior to budburst followed by “softer’’ insect control.

Michael said scale remained reasonably exposed and while longtail mealybug were easier to control, other mealybug can get under bark and into plant roots, proving difficult to control. Mealybug numbers also increase in more shaded canopies.

He said this was where the use of the two-way systemic insecticide, Movento, had been beneficial.

Movento, from Bayer, has only been available for use in winegrapes in recent seasons for control of mealybug and suppression of scale and thrips.

After leaf uptake, most systemic insecticides are mainly translocated in plants’ xylem along with water and nutrients and are transported upwards. Movento is translocated in plants’ phloem as well as xylem, resulting in transportation upwards and downwards to plant parts not contacted by the insecticide. Movento can better control sucking pests hiding on covered inner leaves than other insecticides, as well as populations that may have developed resistance to existing registered products.

It is also highly compatible with other products and with Integrated Pest Management (IPM) production systems, being ‘soft’ on most beneficial species when used as directed, including parasitoids, syrphid flies, lacewings, predatory midges, ladybird beetles, predatory bugs and earwigs.

“It was exciting when Movento became available, because we thought it would give us better control than some of the other products available,’’ Michael said.

“We initially started using it for mealybug, with the idea that it would hopefully suppress scale, but we think it has good potential for controlling scale.

“Mealybug have been in big numbers and we have been happy with the effect on them.

“Even though last season was difficult, Movento still provided good control of mealybug. For control of scale it looks like seasonal conditions, as well as the size of the population to begin with, need to be considered.’’

He also said that while Movento had worked well, careful planning was required for larger vineyards so it could work in with other foliar applications, particularly fungicides.

“In vineyards with a maintenance program, it works really well. With mealybug, it is now the default decision. We will rotate if there are alternatives, but otherwise we will use Movento.’’

Michael said he first became aware of Movento on a trip to New Zealand in 2012. He was impressed with the important role it played in leafroll virus management programs, helping to control the mealybug vector.

Trial work by Landmark, with funding from GRDC, had also shown about 90% control with Movento in the Barossa Valley.

Michael said he was hoping to carry out some further field work with the product in the South East.

About

Category

  • Grower Stories
  • Product News
  • Growers Edge

Date

08 November, 2017

Product

Location

South Australia