Thursday, October 25, 2012

Targeting Light Brown Apple Moth - Q&A

We hear about the Light Brown Apple Moth Controversy. What is this?



Gill

Hi,

Spraying for Light Brown Apple Moth is controversial in the United States because aerial spraying is used for control.  I suggest we wouldn't like that either. It is important to understand the situation in Australian vineyards is different. I have made some notes below.

James

Damage to grapevine tips pre-flowering.

The species is native to Australia and is found in New Zealand, Ireland, the United Kingdom, and Hawaii. It has been classified as a noxious insect in the United States and Canada.

Although it is not known when the moth arrived in the US in 2007 the moth was found in mainland principally along the West Coast in California. Quarantine measures and aerial spraying of cities with pesticides were imposed to try to eradicate the moth. This spraying lead to substantial controversy and reports of adverse health effects. 

Keep reading below about our Australian approach to controlling them.
Targeting Light Brown Apple Moth.
 
The first point is often you don't have to control Light Brown Apple Moth. In many cases their numbers will not be high enough to cause a problem. If levels of Light Brown Apple Moth are low, no action is needed, but in some situations and sites their levels build up.
Light Brown Apple Moth (LBAM) affect fruit quality and greatly increase the chance of Botrytis and other bunch rots in grapevines. The key to controlling LBAM is targeted control, and encouraging beneficial insects to help naturally limit LBAM. Timely control prevents apple moth becoming established in your bunches, and affecting harvest.


Weed Control.

Light Brown Apple Moth start the season surviving in broadleaf plants in and around the vineyard. They survive winter on Eucalyptus trees, Olives, Lucerne and many others. Limiting the amount of broadleaf weeds- Capeweed for example, in turn limits the amount of apple moth that can survive.


Vine Nutrition.

Believe it or not the nitrogen level in your vines influences the level of pest and predator insects in your vineyard. Vines respond to high N fertilizers levels by producing more and larger leaves. These leaves have an elevated level of free Nitrogen. Correspondingly researchers have demonstrated that high nitrogen levels in plant tissue can decrease resistance and increase susceptibility to pest attacks (Link).


Trapping.

The Light Brown Apple Moth that survive winter are seen as adults in early spring. Adult moths can be trapped using pheromone traps and port lures. Monitoring is the key. Each vineyard is unique at it pays to look at it regularly. LBAM numbers and potential damage can vary between sites, regions and seasons it is critical to maintain a monitoring program.


Monitoring.

The first signs of apple moth in spring are seen as egg masses on the developing leaves. These are extremely difficult to spot- picture 1. The time for these eggs to hatch varies from 1 to 3 weeks depending on the temperature.


1. Eggmass.
Once hatched these apple moth grubs are usually found in ‘hot spots.’ Levels are high in isolated patches. Large sections of the vineyard appear clean of the pest. Search in shoots tips looking for small (2-6 mm), light-green and yellow larvae (grubs) pic 2. Good monitoring now will establish the levels in your vineyard allowing you to carefully consider your options in the lead up to flowering (EL 19-25) the critical timing for Light Brown Apple Moth damage


BT's.

A natural control, bacillus thuringiensis (BT), can be applied as an insecticide at this point to control the freshly hatched grubs. BT’s need very good coverage to be successful. In some areas the first hatchings of apple moth are staggered, or uneven compromising the effectiveness of BT’s. If grubs are too big or not yet hatched the BT’s have no effect.

2. LBAM in shoot tips.
Where present, LBAM larvae feed for a week or two before moving to feed on bunches. At this point the caterpillars are easy to find due to grubs causing webbing in bunches pic 3. This is the key time for control. All control options are still available and LBAM levels are easy to detect. 


3. Light Brown Apple Moth damage in bunches at set.
IPM Threshold.

There is no magical number or threshold that signals when a spray should be applied, it is important that this is developed for a particular region, site and variety. In vineyards that are prone to botrytis, LBAM at even low levels can cause a problem and the fruit will need to be protected. Typically a level of 1 apple moth in 10 bunches would cause concern for all varieties.


Insecticide Control.

Insecticide control is an option if pest numbers are significant. When choosing a chemical for control read the label – what is the impact on beneficial insects? Avoid broad-spectrum insecticides – these will only make the problem worse in the long run. Non-selective insecticides have the effect of eliminating natural predators as well as apple moth. Under favourable conditions apple moth numbers increase at a much quicker rate than their natural enemies- causing a population explosion, and crop damage.

Over the last few season new insecticides have been introduced which are designed to be more specific at targeting caterpillars. These include the tradenames; Mimic®, Avatar®, Entrust®, Proclaim® and Success Neo®. Each of these products has pros and cons. Some of them can control LBAM of all sizes, while others are only effective on small growth stages.

More trial work is being performed as to the long-term effects of these sprays on beneficial insects. Keep informed about your control choices. Whatever the results it pays to change your insecticide group every 1-2 years. 
4. Adult green lacewing.
Beneficial Insects.

It is important to look after beneficial insects and let them do the work for you – lacewings (pic 4), parasitic wasps, ladybirds and many other insects can keep numbers below economically damaging levels. Beneficial insects are susceptible to various fungicides and insecticides used in the vineyard, minimising the use of these chemicals is your best weapon against insect damage. Increasing biodiversity in and around your vineyard will also assist with encouraging beneficial insects into the vineyard. Beneficial insects can be your most effective tool in controlling LBAM in the lead up to harvest. A ‘hungry’ predator population will eat apple moth and keep them from eating berries.


Summary.

The key to controlling Light Brown Apple Moth is establishing if you have an issue. Factors like what plants are growing in your vineyard and what your vines nutrition status is will influence the pest level. If needed apply targeted control, eliminating prey and leaving predators behind. An effective LBAM control during flowering sets the vineyard up for a clean harvest. Effective LBAM control ensures numbers are kept to non-damaging levels during flowering- the critical time.

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