NO. 4 LIGHTBROWN APPLE MOTH

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1 NO. 4 LIGHTBROWN APPLE MOTH By Adam Pietsch, Peter Burne and Dino Cotsaris, Viticultural Officers, CCW Lightbrown apple moth (LBAM) [Epiphyas postvittana] is a leaf-rolling moth native to south-eastern Australia. It has since been introduced to and become established in Western Australia and a number of other countries. LBAM is known to feed on over 120 broadleaf plant species, including many pasture plants and horticultural crops, however monocotyledons (grasses) do not support them. LBAM are endemic in Riverland vineyards and may cause significant yield losses and fruit damage in some seasons. LIFECYCLE AND DESCRIPTIONS LBAM have multiple lifecycles through the year. In the Riverland there are typically four generations annually. The generations can overlap and annual fluctuations in the timing of each generation occur due to climatic variations between years. The lifecycle completion time is food source and temperature dependent, with cold conditions slowing LBAM development. In the Riverland heat waves may kill many of the eggs and young larvae, whilst cooler seasons can favour LBAM populations. 1. Eggs Pale blue-green eggs are laid in masses of in a scale like fashion (Figures 1 and 2). The eggs are laid on the upper surface of expanded leaves, generally on leaves near the base of shoots during spring and in the middle of shoots during summer. The eggs darken and hatch after one to three weeks, depending on the temperature. 2. Larvae (caterpillars) The LBAM larvae have six growth stages (instars). The first instar is pale yellow in colour and only 1-2mm long. They disperse, generally moving to shoot tips in spring and to bunches from flowering onwards. Second instars are yellow brown and may turn pale to medium green with a central dark green stripe and a brown head as they mature. The subsequent instars are green and increase in size up to 15-20mm long (Figure 3). Larvae construct a feeding site, using silk threads to roll leaves or tie berries together. 3. Pupae Pupation may occur at the feeding site or in leaf litter on the ground. As pupae mature they turn brown in colour (Figure 4). This stage lasts for one to three weeks, after which a moth emerges. 4. Moths The moths are buff brown in colour and about 10mm long. They become active from dusk onwards and are favoured by mild warm conditions. The males are approximately 20 percent smaller than the females and have darker markings on their wings (Figure 5). The moths mate soon after emerging from the pupae and have a lifespan of two to three weeks. Female moths have the potential to lay 200 to 450 eggs. CCW Co-operative Limited Page 1

2 Figure 1: Freshly laid egg mass (Source: Greg Baker, SARDI) Figure 2: Viable egg mass about to hatch (Source: Greg Baker, SARDI) Figure 3: LBAM larvae Figure 4: LBAM pupae (Source: Diseases and Pests) Figure 5: Female (left) and male moths (Source: Greg Baker, SARDI) Figure 6: Damage to bunch and leaves at feeding nests DAMAGE Evidence of LBAM activity can be found on the leaves, inflorescences and bunches. Feeding sites are constructed by larvae, using silk webbing to roll or join leaves, flowers and berries together (Figure 6). The winter generation of larvae survives on broadleaf cover crops and weeds, unharvested bunches and other fruit crops (eg citrus). As the moths of this generation emerge they can move into the young vine canopy, laying eggs on the foliage. The damage to developing shoots and inflorescences inflicted by this new generation of larvae is generally minimal. In rare situations buds can be destroyed and fruitfulness may be reduced. In the Riverland the late spring generation through flowering can inflict significant damage. Each larva destroys on average 25 potential berries. There is generally little evidence of this physical damage at harvest, with the damaged berries often dropping from the rachis. Damaged flowers and berries that do remain attached provide sites for latent Botrytis rot infections, which can reactivate after veraison causing bunch rot losses. Throughout the season the larvae can continue to feed within bunches. Bunches provide ideal feeding sites after bunch closure. This is especially so for varieties with compact bunches. Chardonnay, Pinot Noir, Sauvignon Blanc, Semillon and Grenache are generally considered the most susceptible varieties, although none are resistant. On average each larva damages 15 developed berries through surface feeding and penetration. Damaged berries can dry and shrivel and are more susceptible to bunch rot infection, particularly by Botrytis and Aspergillus species. Larvae chewing the rachis can kill branches of bunches, further increasing yield losses. MONITORING LBAM monitoring involves regular and careful inspection of the vineyard throughout the season. It helps determine whether pest numbers are high enough to necessitate control and what management options will be most effective. Monitoring should also occur after implementing control measures to evaluate their effectiveness. CCW Co-operative Limited Page 2

3 Monitoring for LBAM is particularly important in high risk vineyards. A good example is Chardonnay with a broad leaf cover crop and a history of LBAM. In many situations monitoring can be focused on the high risk blocks, which act as an early indicator for the rest of the property. Monitoring moths LBAM moth activity can be monitored by using pheromone or port wine traps. The pheromone traps use a synthetically made female pheromone to specifically attract male LBAM. They enter the trap and get caught on a sticky surface, allowing easy counting at inspection. Port wine traps use a ten percent solution of port wine, attracting a wide range of insects that drown in the solution. Correct identification of the LBAM moths is required and can be difficult. Traps are placed within the vine canopy across the vineyard, with three pheromone or five port wine traps generally sufficient for 40 hectares. These should ideally be checked twice weekly from budburst to harvest, with the numbers recorded so peak periods of moth activity (flights) can be identified. Flights can be used as an indicator for egg laying, but are generally not a good predictor of the future larvae population size. It is also a useful guide for the timing of more intensive egg mass and larvae monitoring. The time between flights and hatching can be as short as twelve days in spring and seven days in the summer if conditions are favourable. Monitoring egg masses and larvae When monitoring for LBAM egg masses and larvae examine 100 random shoots throughout the vineyard on a weekly basis. Look at all the leaves and bunches for egg masses and feeding sites containing larvae. It is a good idea to keep track of the shoot sample number by using a handheld counter. Make note of the number, size and location of all larvae found. The colour of egg masses should also be recorded, as this indicates the state of the eggs (Table 1). The viable egg masses should be circled with a permanent marker, the leaf tagged and the date recorded. This allows the egg development to be monitored over the following days/weeks and subsequently control measures to be aimed at newly hatched larvae. Table 1: Egg mass colours Egg mass colour Green Yellow, black spot White/clear Black State of eggs Freshly laid and viable Viable and about to hatch Already hatched Parasitised Young larvae, first and second instar, are often found within the growing tip of the shoot, but later in the season they can move directly into bunches. Searching for larvae in the shoot tip requires the young expanding leaves to be pulled apart. Folded over leaves and webbing in bunches often gives away the location of feeding sites containing larvae. When searching for larvae care must be taken as they have the tendency to rapidly wriggle and drop to the ground or hang from a silk thread when disturbed. Table 2: Monitoring LBAM LBAM How to monitor When to monitor Common threshold* lifecycle stage Egg masses Inspect the upper side of expanded leaves on 100 shoots Once first leaves have expanded and then throughout the season >3 viable egg masses per 100 shoots Larvae on shoots Larvae in bunches Inspect shoot tips and webbed together leaves on 100 shoots Inspect inflorescences and bunches on 100 shoots Throughout the season From inflorescence development onwards >20 larvae on foliage per 100 shoots >10 larvae within bunches per 100 shoots CCW Co-operative Limited Page 3

4 * Note: If the observed pest density is clearly above the threshold, control options should be considered. If the pest density is close to the threshold, further monitoring of an increased sample size may be required before a management decision is made. Thresholds depend on what is being monitored, the seasonal conditions, the susceptibility of the variety to Botrytis rot and the time of the season. Additional monitoring tools that can be utilised in the Riverland are CropWatch SA and the CCW Advisory service. Commercial monitoring services are also available. CONTROL OPTIONS There are four major control options. They are: 1. Cultural control The common approach to cultural control involves minimising the amount of winter host broadleaf plants growing on the vineyard floor, particularly before budburst. This includes weeds, such as capeweed, dock and ribwort, and broadleaf cover crops (eg clovers and medics). Effective broadleaf weed control and using cover crops that do not host LBAM (eg cereals) will limit the over-wintering sites. A diverse cover crop with some LBAM hosts may allow a balance of pests and beneficial insects to coexist. There is no hard and fast recommendation about which cultural approach is most suitable. Research into the interactions between vineyard floor management, i.e. broadleaf free or not, and LBAM populations is currently lacking. Decisions should be based on site specific information (eg variety, history and previous experience). 2. Biological control Since LBAM is native to Australia, there are usually many native biological control agents (natural enemies) commonly coexisting with it in the vineyard. These include the following: Table 3: Natural enemies of LBAM Target Action Name of beneficial and comments Egg mass Parasitoid Trichogramma spp. the wasps lay eggs in the LBAM egg mass Larvae Predator Lacewing Micromus spp lacewing larvae are predacious Shield bugs Oechalia schellenbergii Spiders many types Larvae Parasitoid Voriella uniseta flies maggots grow on outside of larvae Dolichogenidea tasmanica wasp white cocoons found in feeding nests (Figures 7 and 8) Larvae Pathogen Nuclear polyhedrosis virus (NPV) Pupae Parasitoid Brachymeria phya wasps Moth Predator Spiders many types In many low pressure situations natural enemies can kill up to 90 percent of each LBAM generation, keeping numbers in check. Encouraging natural enemies can help maintain their populations and therefore provide continual control. For example, a diverse range of plants on the vineyard floor provides alternate food sources, promoting natural enemy populations. Broad spectrum insecticides will kill the predators and parasites and should ideally be avoided. CCW Co-operative Limited Page 4

5 A number of beneficial insects are commercially available for release in vineyards. One example is the Trichogramma carvarae wasp. Several releases of ,000 wasps per hectare through spring can give effective control. In high pressure situations biological control may not sufficiently suppress the LBAM populations. If a chemical for LBAM control is required, the impact on the natural enemies should be considered. Softer and biological chemicals are available, as outlined under Spraying control. Figures 7 and 8: A parasitoid of LBAM, Dolichogenidea tasmanica (Source: Cate Paull, University of Adelaide) 3. Mating disruption A number of vineyards across Australia use slow release synthetic sex pheromones to disrupt LBAM lifecycles. Twist-tie dispensers of the synthetic pheromone are introduced throughout the vineyard at 1000 per hectare. Dispensers are applied prior to budburst, preferably in August, before LBAM spring flights. The natural pheromones released by the female moths are swamped by the introduced synthetic pheromones, hindering the male moth s ability to find females. Subsequently very few viable egg masses are laid and the number of larvae in the following generation are substantially (up to 95 percent) reduced. An advantage of mating disruption is that it is specific to LBAM, although a minimum treatment area of 10 hectares is generally required for success. Extending the synthetic pheromone treatment into surrounding areas may be required to decrease the risk of mated females migrating into the vineyard. 4. Spraying control When thresholds are exceeded and unacceptable levels of damage are imminent, spraying is often the only option left for growers. The types of sprays available are outlined below: Table 4: Spraying control options of LBAM Type Pros Cons Sprays active constituents Biological Bacillus thuringiensis (eg Delfin WG, Dipel DF, Full- (BT) Bac WDG ) New generation ( softer ) Does not harm natural enemies Relatively cheap Can be used up to harvest Provide improved LBAM control with decreased toxicity to natural enemies Only effective on early instars (1-3) Broken down by UV light, only lasting up to 72 hours Relatively expensive Greater restrictions on use Tebufenozide (eg Mimic 700 WP ) Spinosad (eg Entrust Naturalyte, Success Naturalyte ) Emamectin (eg Proclaim ) Indoxacarb (eg Avatar ) Broad Effective control of all May decimate natural enemy Carbaryl spectrum instar stages populations, potentially Chlorpyrifos causing upsurges of other pests Greater restrictions on use Check the current spray diary for registered products and their restrictions on use. Critical factors to consider for effective spraying of LBAM include: Appropriate choice of product Timing Spray coverage and rate Compatibility with other chemicals Withholding periods CCW Co-operative Limited Page 5

6 IMPORTANT Growers should ensure they follow both the registered product label instructions and Constellation Wines Australia s spray diary requirements at all times. Occasionally there are important differences that growers will need to clarify through CCW viticultural staff. Failure to comply with both the label instructions and Constellation Wines Australia s spray diary requirements may constitute a breach of HACCP. Contact the winery before using broad spectrum insecticides. This section will be updated by CCW when new products and information become available. Feel free to seek further advice and information from the CCW Viticulturalists. FURTHER INFORMATION 1. Disease and Pests, Grape Production Series Number 1. (Nicholas P, Magarey P and Wachtel M) Winetitles Adelaide The Australian and New Zealand Field Guide to Diseases, Pests and Disorders of Grapes. (Magarey PA, MacGregor AM, Wachtel MF and Kelly MC) Winetitles Citrus pests and their natural enemies: integrated pest management in Australia. (Smith D, Beattie GAC and Broadley R) Queensland Department of Primary Industries IPM Viticulture: Research to Practice. (Shanks A, Braybrook D and Aitkin D) Cooperative Research Centre for Viticulture, 2000 ACKNOWLEDGEMENTS Fruit Doctors Pty Ltd., for help in editing this Fact Sheet. Greg Baker, SARDI, and Cate Paull, University of Adelaide, for photographs. Figure four was reproduced from Diseases and Pests, Grape Production Series No. 1 (Nicholas P, Magarey P and Wachtel M) with permission. DISCLAIMER The information supplied in the Fact Sheet was the best available at the time of publication. However, the understanding and control of pests and diseases is constantly evolving and recommendations regularly change. The reader should seek a professional opinion before acting upon information in this Fact Sheet and should always comply with the winery s requirements and recommendations, food safety legislation and the information on chemical product labels. All rights reserved. No part of this publication can be reproduced or copied without the written consent of CCW Co-operative Limited. Published by CCW Co-operative Limited Box 238, Berri, South Australia 5343 Telephone (08) Facsimile (08) For further information contact Mr Peter Burne, Senior Viticulturalist CCW Co-operative Limited Page 6