Best practice eradication
Learnings from European grapevine moth eradication efforts in Napa, California.
While in the US on a study tour in September, Vinehealth Australia Technical Manager Suzanne McLoughlin met with Monica Cooper and Lucia Varela, University of California Cooperative Extension Farm Advisors, to discuss efforts in controlling, containing and ultimately eradicating Lobesia botrana (European grapevine moth). This article provides insight into the collaborative approach taken to eradicating this exotic pest, which earnt program leaders a federal Administrator’s Award in September 2012. What can we in Australia learn from this?
Native to Mediterranean Europe, the European grapevine moth (Lobesia botrana) is a serious pest of grapes. It has invaded Europe, west Asia, North Africa and East Africa, Middle East, eastern Russia, and was detected for the first time in Chile in April 2008, in California in September 2009; and in Argentina in April 2010 (Ioriatti et al. 2012 and Varela et al., 2013).
Grape is the preferred host and larvae feed on flowers, and on or inside both green and softening berries (Smith et al, 2010).
In the United States, the first detections were in the Napa county, California, where this invasive pest and associated fungal rot caused significant crop damage in 2009. Crop loss of $150,000 was reported in the vineyard in which L. botrana was first detected.
How did the wine industry respond? With a coordinated, award winning eradication program.
Setting the plan of attack
Getting the right people around the table
Within 2 months of detection, the United States Department of Agriculture, Animal and Plant Health Inspection Service (USDA APHIS) agency put in place a Technical Working Group (TWG) of subject-matter experts, comprising federal, state and county government personnel, researchers, extension staff and a representative of the winegrape industry. The group was tasked with providing urgent scientific recommendations to regulatory program managers in California.
International scientists were also identified and engaged from Italy, Spain, Chile, France and Germany, and invited to be part of this group. These specialists were imperative to share knowledge; particularly the Chilean who had dealt with an incursion a year prior. The Chilean management program was in fact replicated in the first instance for the Californian situation.
While vines were dormant over winter 2009, the TWG of 11 had time to develop of plan of attack. They recommended to pursue eradication in California provided that:
- The botrana population did not become substantially more widespread than was recorded in 2010;
- The grape industry remained supportive of the effort; and
- Control methods available in 2010 remained available for use by the program (Varela et al., 2015).
Five University of California staff travelled to Chile to visit the Chilean Department of Agriculture and review the Chilean eradication approach. This visit also served to forge a tight relationship between both countries, which proved invaluable during the six years it took to eradicate L. botrana from the Napa.
Setting the eradication strategy
The TWG set an eradication strategy as follows:
- Identify the geographic range of the insect in California;
- Develop and implement detection and management programs;
- Regulate the movement of plant material and equipment to minimise the threat of dispersal;
- Incorporate research-based information developed by subject-matter experts into policy decisions; and
- Promote a wide-reaching educational program for grapegrowers, the public and local officials.
The activities of this strategy drastically reduced insect populations and limited the distribution in Californian vineyards such that previously affected areas were removed from quarantine. Within six years, L. Botrana was eradicated.
Value of conducting research in parallel with outbreak management
In previous quarantine situations, research had not been allowed inside a quarantine zone. However, a new approach was taken by the TWG to ensure tight collaboration between extension and research staff, which meant work was done in parallel to eradicate the pest. This proved vital.
An extensive literature review was conducted focussing on pest biology and control measures, identifying three generations of the moth in a season. This review included translation of many papers and articles from numerous countries, to ensure all decisions made by the TWG were informed by science. Comprehensive extension material was produced; initially published via the web and then in brochure and poster formats.
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Gauging the enormity of the problem
Monitoring of male moth flights was undertaken both outside and inside the quarantine zones using pheromone-baited sticky traps. Traps were distributed by government staff on a standard 10 traps per km2 grid system for planted vineyard inside a quarantine area and at three to six traps per km2 outside a quarantine area.
In urban environments, traps were placed on potential host species at a density of two traps per km2. These traps gave the TWG a guide as to hotspot areas where additional surveillance could be deployed at a higher density. It also offered a guide to initiation and peak of flights, to help time insecticide applications for larval emergence. Monitoring for larvae and egg masses was also undertaken.
In 2010, the largest moth populations were found in the Napa County at 100,831, compared to 128 total moths in the remaining counties (Varela et al., 2015). In 2011, at peak quarantine activity, there were 10 regulated counties in California with monitoring activity covering a vineyard area of approximately 61,000 hectares out of a total 605,000 hectares. The monitoring of male moths was highly successful for demonstrating the effectiveness of the eradication effort and ultimately leading to eradication across California (Table 1).
Table 1. Number of L. botrana male moths trapped in Napa County and traps deployed at peak trapping (modified from Varela et al., 2015 and Eberling, 2015).
|Males moths trapped
Identifying host plant species
Pheromone traps and treatments were deployed in all potential host species of L. botrana, including blackberry, elderberry, olive, wild rose, wild and domestic grapes, wild and domestic plums, peach, nectarine, blueberry and gooseberry (a host list of 40 species, but true hosts were few and grape was identified as the favoured host).
Olives were found to be a minor host of L. botrana, but only to the first generation, as flowers were the preferred feed source.
The TWG identified that L. botrana did not venture into commercial crops other than grapes in California. Eradication probably wouldn’t have been possible if this wasn’t the case.
In the Chilean scenario, the insect spread to blueberries, significantly hindering prospects of eradication. In addition, the number of backyards in California with vines was relatively low and therefore L. botrana was relatively easy to contain. Riparian zones were also feared initially to be a habitat for the insect, however wild grapes growing along the river courses were found to be less preferred compared to commercial vines, because of the lack of fruit which was often hard and late maturing.
Identification of these host species on a landscape level was critical to the eradication effort in terms of trapping. Digital land use maps were available to identify location of host plants. Location of commercial vineyards was also well known, but location of urban vines proved an issue initially. In the first year of the eradication effort, many of the urban properties with vines were unidentified and subsequently fell through the cracks for treatment or fruit removal, but this was addressed thereafter.
Setting up quarantine zones
In the first year of the eradication strategy in 2010, a conservative approach was taken to setting up quarantine zones, also known as ‘regulation’ zones. These were established in an 8km radius of a detection, where a detection was defined as either:
- Two or more adult moths trapped within 5km of each other during the same life cycle; or
- Immature stages proved to be botrana by DNA analysis.
In June 2010, a federal order indicated plant host species as well as plant parts, products, farming and processing equipment, and green waste residues could not be transported interstate from a European grapevine moth quarantine area, except under specific conditions. State quarantine enforced restrictions parallel to those in the federal order, for intrastate movement of regulated items within or from quarantine areas. Businesses were required to sign compliance agreements that mandated specific activities prior to and during harvest, transport, processing and waste handling (Cooper et al., 2014).
Continual research into the biology of the insect determined that it was in fact a weak flier, flying less than 50m in distance. With this additional knowledge, the 8km quarantine zone was reduced to 5km by 2013, and the treated area reduced to 500m from the point of detection occurring in the current year and previous two years.
Qualifying for deregulation from quarantine status
The TWG recommended that all portions of an entire contiguous regulated area should be deregulated at the same time, and specified a range of conditions underpinning qualification for deregulation:
- No moths captured during five consecutive generations;
- Insecticide treatments to continue to target the first and second generations;
- Mating disruption may not be used during the final two generations within the area under regulation; and
- During these final two generations, trap density must increase to 39 traps per km2 in all vineyards within 500m of previous detections.
Based on the above criteria, four counties were removed from regulation at the beginning of 2012. By the end of 2012, another three counties were fully deregulated and two counties partially deregulated, leaving Napa county and parts of Sonoma and Solano counties remaining under regulation in 2013.
Further changes to the deregulation conditions advised by the TWG were:
- High-density traps at 39 traps per km2 deployed county-wide must be free from detections during four full flights; and
- Any moth captured will trigger the delimitation and establishment of treatment areas within 500m of the detection.
Because of these changes, trap density nearly tripled in Napa County in 2013. The remainder of the Solano county and most of the Sonoma county, as well as southern Napa County were deregulated in 2014, leaving the remainder of the Napa Country and a small portion of northern Sonoma County of 115,500 hectares regulated during 2015.
No moth was detected in 2015 or in the first two flights of 2016. As a result, L. botrana was declared eradicated from California in August 2016.
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Management of winery waste
While it is still unclear as to how L. botrana entered the state of California, winegrape movement was deemed the movement vector responsible for spreading the pest within the state. In addition, spread also occurred by machinery moving between vineyards.
One research project focussed on investigating potential pest spread through the movement and treatment of winery waste. Results showed that winery waste was not a large contributing factor to spread, as L. botrana was killed during the (whole bunch) pressing stage when pressed to 28 psi. However, accidental spills of grape matter were found to be a potential mechanism for spread in the winery, so cleaning disassembled winery machinery with hot water was found to be critical.
During the quarantine period, a mandated practice was that all stalks and stems were required to be properly composted inside the quarantine zone, to ensure specified temperatures were reached to kill the insect. In practice, this meant composting at commercial facilities.
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Action in the field
The eradication strategy involved the use of three tools – insecticides, pheromone-based mating disruptors and host removal, which varied in combination based on land use and occurrence of potential host species. In the urban environment, fruit removal from backyard grapevines in spring or early summer was the preferred approach.
Identifying insecticides and timing of applications
In the first year, two large insecticide research trials were undertaken. Every registered insecticide for use on grapes was evaluated for effectiveness to kill L. botrana eggs and larvae, to ascertain whether ‘soft’ products were as effective, to identify off-target issues and to test effects on beneficial insects. This was important research given both conventional and organic management systems needed to be provided for. In Chile, pyrethroids were commonly used because they were cheap, but these products burnt the vine canopies. Chemical registrations for the affected counties also had to be assured.
These research trials determined insecticide options to be used in conjunction with mating disruptors for non-organic growers – Intrepid (chlorfenapyr) and Altacor (chlorantraniliprole), for use in alternation for each moth flight. For organic growers, Bacillus thuringiensis (Bt) and Entrust Naturalyte (spinosad) were identified. The latter was not used by growers, however, due to cost. A limited product list allowed fewer negotiations with chemical companies to ensure sufficient product was available for the eradication effort. In addition, fewer product choices meant that varying efficacy did not affect the eradication effort.
Timing of insecticide applications played a very important part in leading to the eradication of L. botrana. Through literature reviews, the insect was known to complete two to five annual generations, as determined by latitude, climate and microclimate (Ioriatti et al., 2012). Local research using temperature modelling, predicted three generations per year in the Napa Valley, which was then validated through ground observations (Gutierrez et al., 2012).
A subgroup of the TWG met every week to revise the spray schedule for growers, based on degree days, to model the lifecycle development of the insect. Insecticide applications were timed to coincide with the most vulnerable stages of the pest. Grape flowers were determined to be more nutritious than berries for the insect and therefore a higher number of degree days was required for development of the second and third generations (which coincide with infections on green berries and softening berries respectively) so degree day intervals for spraying increased from the second generation onwards during the season. A three-week window was instituted around each spray timing, to allow the required insecticide applications to be tank mixed with other agrochemicals to limit additional passes.
Peer pressure between growers to follow the quarantine requirements during the incursion appeared more effective than the issuing of fines for non-compliance.
Despite chemical registrations being in place for use on grapes, work had to be done with chemical companies to register products for use on olives.
Once preferred products were identified, discussions with manufacturers occurred in attempt to gain registration for use in affected crops in the required counties. Some chemical companies did not chose to take out registrations for their products for this cause.
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The use of mating disruptors in the form of ISOMATE pheromone dispensers applied over large, contiguous areas, in conjunction with well-timed insecticides, were found to be very successful in controlling L. botrana. Significant research was undertaken by the TWG to evaluate the efficacy and longevity of four pheromone lures before a suitable lure was chosen, approved and registered for use.
Mating disruption works by using many ISOMATE dispensers (ISOMATE®EVGM twist-ties), applied by hand at 200 dispensers per acre, to saturate the air with synthetic female sex pheromones which confuses the male moths and renders them unable to locate females, suppressing mating and therefore crop damage. Although mating disruption does not completely inhibit L. botrana mating, delayed mating reduces populations because older females produce fewer eggs than younger females (Torres-Vila et al., 2002).
Communicating the eradication strategy
Program leaders provided transparent, consistent, timely and coordinated communication to parties directly and indirectly affected by the eradication effort (Cooper et al., 2014), which became a hallmark of the program.
Toll free number
A toll free number was established for reporting possible L. botrana finds.
A range of education materials was used to communicate to growers, winery personnel and the public. These included brochures, posters, a training video, postcards, door-hangers, magnets, billboards, signs, radio announcements, social media and websites.
Well before any spraying was scheduled, community meetings were held in Napa and Sonoma to engage environmental groups in the eradication strategy, given their concern after the aerial spraying efforts in 2007 for Lightbrown apple moth. Multiple public meetings were also held, involving the international specialists. In each year of the eradication strategy, a meeting open to the public was held where growers and community members could pose questions to the TWG.
Having a single unified message was vital to avoid confusion. This included the same PowerPoint presentation and talking notes used to communicate the science at all meetings within the county.
Countless field days were held, both in English and Spanish, showing growers how to look for and identify L. botrana egg masses to aid in identifying hotspot areas in the quarantine zones. All communication materials produced were bilingual.
Weekly electronic newsletters were prepared and distributed from early in the eradication plan, providing stakeholders with real time updates and photographs on progress and tasks being undertaken. This information was then used by individual wineries to train their public-facing staff, for example cellar door and customer relations staff. In addition, grower liaison staff played a central role in information dissemination.
Extension staff found that growers were more likely to report and discuss issues when in small groups. Grower groups of around 20 growers were set up as ‘safe’ places to have open discussions. Extension staff found that initially they were doing all the talking, but gradually growers started sharing their experiences among their peers in these forums.
Hobby winemakers were identified as an ‘at risk’ group to contributing to the spread of L. botrana through their movement of grapes; often moving grapes from the Napa to other states. In addition, this group generally falls outside the commercial winemaking groups, meaning they have less access to information.
Reaching this group was considered an issue. However, it was identified that hobby winemakers often belonged to clubs, which were listed on the internet. The TWG contacted these clubs and presented at numerous meetings to ensure this target group was armed with required knowledge about the eradication strategy and the role they played in it.
Carriers were another core group identified for targeted communication. At the beginning of the eradication effort, loads were instructed to be tarped to minimise potential hatching of the larvae and transfer into vineyards en route to the winery. However, an increase in load temperature due to the tarps was touted to ruin wine quality. As a result, transporting to reduce spillage specifications were instead put in place. For hand-picked fruit, bins were not to be filled within 300 mm of the lip of the bin and even more for machine picked fruit.
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While grapegrowers did not contribute extra levies to the L. botrana eradication strategy, they were responsible for paying for and applying the required insecticides. Application of mating disruptors was not adopted as effectively as the insecticides, with only approximately 50% of growers applying them in the first full year of the strategy in 2010. The following year, a grant was obtained which paid for the pheromone dispensers, which growers then applied.
A state-wide spend of at least US$105 million has been reported for the L. botrana eradication activity. USDA contributed US$46.5 million, Napa County spent US$9.8 million and the wine industry, US$49 million, with activity including trapping, insecticide application and quarantine compliance (Eberling, 2015).
Given the value of the grape industry at more than US$4 billion in California alone (European Grapevine Moth Post-Eradication Response Working Group, 2016), the high cost of the eradication program for L. botrana at more than US$100 million was justified, along with maintaining a robust and sensitive early detection trapping program for the insect.
Despite being extremely busy managing the incursion activity, one initially unforeseen activity by the TWG was the interest shown from overseas personnel (some interest linked to export markets) who wanted to observe, in person, the eradication activity.
Although the largest L. botrana infestation in this case was in a winegrape producing region, adults were detected in very low numbers in a table grape vineyard in the Central Valley of California. Significant economic impact to the Californian table grape industry could have resulted from export restrictions imposed by importing countries (Varela et al., 2015).
For three years’ post eradication, pheromone-baited trap monitoring continues for L. botrana in grapegrowing areas of California and the United States, as part of early detection programs.
A postdoctoral researcher in the Department of Entomology at the University of California, Riverside is studying the spatiotemporal dynamics of the L. botrana invasion. The dataset of moth distribution from the years of monitoring is being used to understand the factors that contributed to moth establishment and spread, and to evaluate the efficacy of regulatory procedures.
Major lessons learned
- When faced with an incursion, the first thing to assess is whether it’s even possible to eradicate, based on money, time, resources available and pest host range. The ease and success of an eradication effort is far more likely for an insect with a limited host range.
- All participants in an eradication effort need to be on board.
- Having extension staff as part of the TWG playing an impartial role between the regulators, researchers and growers was important to ensure the needs of all parties were met when devising the eradication strategy.
- Permitting researchers to undertake research concurrently with rolling out the eradication strategy hastened learnings and practical solutions.
- Ensuring research funding bodies were at the table from the start meant research priorities were identified and appropriately funded.
- Availability of a continual funding source at the required level for the life of the eradication strategy allowed the strategy to be fully implemented, contributing greatly to the result.
- Communication to industry personnel must continue post eradication, to ensure recognition of the pest, so that any new outbreaks are rapidly identified.
- A single, unified message to industry and community is vital to ensure no confusion of message.
- Effective control measures must be available for use.
- Stakeholder networks must assist in communicating messages. This will be the fastest way to reach everyone.
- Transparency and honesty is key – distrust takes a long time to repair.
- Don’t make assumptions.
- Learn from previous eradication efforts around the world.
- Cooper, M., Varela, L., Smith, R., Whitmer, D., Simmons, G, Lucchi, A., Broadway, R and Steinhauer, R. (2014). Growers, scientists and regulators collaborate on European grapvine moth program. California Agriculture. October-December. https://californiaagriculture.ucanr.edu
- Eberling, B. (2015). European Grapevine Moth nearing eradication – from the Napa Valley Register. CDFA Planting Seeds Blog https://plantingseedsblog.cdfa.ca.gov/wordpress/?p=9276
- European Grapevine Moth Post-Eradication Response Working Group (2016). European Grapevine Moth Post-Eradication Response Guidelines. Report.
- Gutierrez, A.P., Ponit, L., Cooper, M.L. et al. (2012). Prospective analysis of the invasive potential of the European grapevine moth Lobesia botrana (Den. & Schiff.) in California. Agr Forest Entomol 14:225-238.
- Ioriatti, C., Lucchi, A. and Varela, L. G. (2012). Grape berry moths in western European vineyards and their recent movement into the New World. In: Bostanian, N.J., Vincent, C, Isaacs, R. (eds). Arthropod Management in Vineyards: Pests, Approaches, and Future Directions. Springer Science + Business Media B.V. p339-359.
- Mastro, V., Carde, R., Lance, D., Lucchi, A., Sazo, L., Steinhauer, R., Varela, L. G. (2010). Second report of USDA APHIS International Technical Working Group for the European grapevine moth in California. May 14, 2010 6pp.
- Smith, R. J., Varela, L. G., Cooper, M, L., Bentley, W. J. and Bettiga, L. J. (2010). European Grapevine Moth (Lobesia botrana) brochure. University of California Agriculture and Natural Resources.
- Torres-Vila, L. M., Rodriguez-Molina, M. C., Stockel, J. (2002). Delayed mating reduces reproductive output of female European grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae). B Entomol Res 92: 241-249.
- Varela, L. G., Cooper, M. L. and Smith, R.J. (2013). Can European grapevine moth, Loesia botrana (Lepidoptera: Tortricidae) be eradicated from California? In: Calonnec, A., Duso, C., Gessier, C. et al. (eds). IOBC/WPRS Bulletin 85: 92-102.
- Varela, L. G., Cooper, M. L., Lucchi, A. (2015.) Update on Lobesia botrana Program in California. https://www.iobc-wprs.org/pub/2015_WG_Viticulture_Vienna/20151022_09_IOBC_Vienna_Entomology_Varela.pdf
 Confirming that L. botrana was reproducing at the detection site, and not just transported to the detection site, as could be the case for a single moth.
 Not registered for use on grapes in Australia at present