Article taken from The Fruit Grower, written by Sue Jupe
30 January 2017
After three years of UK trials, BASF, working with Agrovista, has launched the first multi-pest pheromone disruption system, named RAK 3+4. Already commercially abailable in Europe, orchards are flooded with high rates of synthetic pheromones, and male moths become confused and give up trying to find a mate – mating is disrupted. With consumers being particularly wary of pesticide residues in fruit, this new approach to pest control in top-fruit offers real benefits for the control of challenging moth species.
Setting the scene, Simon Townsend of BASF said that, in line with other sectors of the industry, top fruit growers have lost valuable actives in the past 15 years following EC Regulation 1107/2009, changing the emphasis on plant protection products from a risk-based to a hazard-based system. Pest and disease challenges have been further compounded with growing biological resistance to some remaining actives.
Following approval through a mutual recognition label in Belgium, UK top fruit growers have a new IPM (integrated pest management) tool – RAK 3+4 – a mating disruption system for Codling Moth (Cydia pomonella) and Summer Fruit Tortrix (Adoxophyes orana). In addition, trials have produced observed efficacy against other Tortix species including Large Fruit Tree Tortix and Dark Fruit Tree Tortrix.
Adult Codling Moths emerge from cocoons in spring. Eggs laid on leaves and developing fruit hatch after a short time and the resulting larvae immediately bore into the fruit making control with insecticides difficult. As the moths directly damage the crop, the economic threshold is very low.
Importantly, in August or September there can be a partial second generation and, according to Agrovista’s Paul Bennett, this is particularly problematic as it necessitates insecticides being applied close to harvest. Whilst growers must adhere to strict harvest intervals, spraying at this stage has the potential for detectable residues to be found on the fruit, he warns.
Among the existing plant protection product options for Codling and Tortrix Moths are the ovicides Chlorantrantiliprole (Coragen) and Fenoxycarb (Insegar) and larvicides Spinosad (Tracer) and Methoxyfenozide (Runner).
How does it work?
As with all good IPM systems, the pest population should be monitored using an appropriate pest forecasting system or monitoring traps. “The new RAK 3+4 mating disruption system relies on the pheromones being in before the first target moths take flight in spring – around Arpil and before the end of the blossom,” explained Simon Townsend. “Designed to give season-long control, the pheromone cloud is released over nine months through to October.”
Simon went on to explain that in nature, female moths emit pheromones producing a concentration gradient which males travel down to locate a mate. “By releasing high rates of synthetic pheromones, male moths become confused and give up trying to locate a female. Mating is disrupted, no fertile eggs are laid and the population reduces,” he says.
With RAK 3+4, volatile female pheromone vapours are released from brown ampoules, each with two chambers – one containing Codling Moth pheromone the other Tortrix pheromone. By using multiple dispensers, a confusing cloud of pheromones is produced. BASF recommends that dispensers are used at a rate of 500 units/ha – at a uniform density of approximately one per 20 sq. metres. To prevent moths from adjacent areas encroaching into the treated orchard, and to maintain pheromone concentration at the edge of the treated area, additional product must be placed at the borders. BASF recommends doubling the dispenser rate at the edges of the treated area – such as orchard edges and along roads through orchards. “the dispensers should be hung in the top third of the tree, as the vapour is heavier than air, and at varying heights to achieve a ‘muddled’ vapour plune,” explained Simon Townsend. “The dispenser should be positioned so that it is clear of the body of the tree.”
To check efficacy during the season, pheromone monitoring traps (that attract male moths) should be installed in the treated orchards and checked weekly. If these traps no longer catch moths, this indicates that RAK 3+4 is working properly. However, it is always possible that mated females may enter the treated orchard from outside, and it is therefore important to check for fruit damage during the season. If the latest monitoring thresholds are exceeded, this is an indication that the moth population is too high, meaning that treatment with RAK pheromones alone may be insufficient. In this case, treatment with a conventional insecticide is necessary.
UK trials at Wisbech Contract Farming
Trials over several seasons at Wisbech Contract Farming in Norfolk have produced impressive results.
A modern progressive fruit farm, the highly uniform GPS-planted orchards employ modern post-and-wire hedgerow systems. Working closely with Paul Bennett of Agrovista, John Portass of Wisbech Contract Farming has trialled RAK 3+4 for the past three years on a total of 8ha.
The RAK 3+4 ampoules were distributed from a picking platform at the same time as workers carried out other operations, and took approximately 12 man-hours/ha. “In the first year of trials we selected an orchard with low moth pressure,” explained John. “The results gave us the confidence to extend the trial in the second year to a higher pest-pressure orchard. With no moths recovered in the traps we didn’t need to spray at all. We had extremely low level damage in fruit of just 1 or 2 per 1000 and as the season went on the moth population reduced.” In comparison, in untreated areas 60-70 codling-affected apples per 1000 fruit were recorded.
Summarising the results at the end of the third year of trials, Codling Moth numbers had been reduced by 95%, Summer Fruit Tortrix by over 89% and Fruit Tree Tortrix by over 99%. The economic thresholds were never exceeded and no caterpillar sprays were needed. Putting it in context, Paul Bennett said, “Using conventional pesticides the overwintering population tends to stay the same. Using 3+4 system the background population is reducing year-on-year.”
Impressed with the results, John Portass envisages rolling out the RAK 3+4 strategy to 60-70% of his 90ha in 2017. “We will be using it in high value varieties, such as the scab resistant Opal, but at this stage not the lower value Bramleys,” he says.
Commercial use in Europe
Mating disruption systems are already in commercial use in top fruit in Belgium, the Netherlands, Germany and France. It is estimated that 47% of top fruit in Belgium (7,000ha) currently uses mating disruption, with the RAK 3+4 system accounting for 20% and RAK 3 for a further 20%. While orchards receive a supplementary insecticide when required, or just around the outside rows, monitoring of 34 orchards in Wallonia showed 19 had used no additional insecticide.
According to Simon Townsend, pest pheromone disruption systems have been shown to work well in central Europe, withstanding extremes of temperature, and are already widespread in Germany in various crops, including vines. Trials in Belgium have shown that, compared to a reference orchard, RAK 3+4 delivers a major decrease in the number of males caught in traps and a significant decrease in infected fruit. The mating disruption system also showed a useful effect on many other species of Tortrix Moth including Fruit Tree Trotrix, Rose Trotrix an dMarbled Orchard Tortrix.
Simon Townsend is keen to point out that RAK 3+4 only controls specific moth species – Codling and Tortrix. It is therefore important that growers monitor for the occurence of these pests during the season, particularly at orchard borders. If thresholds are exceeded, BASF recommends that growers use a well-timed insecticide spray in addition to RAK 3+4. Under high pest pressure the level of control from RAK 3+4 can be reduced, making careful monitoring essential. “Growers should be mindful that using mating disruption does not rely on using any broad-spectrum insecticides, so new or past pest species may become a problem and will need to be controlled iwth appropriate IPM measures,” says Simon. “In some UK trials, there has been a resurgence of moth pests that have not previously been a problem (for example, Blastobasis sp). Other moth species not controlled that are potential pests in top-fruit include Spilonota sp and Epiphyas sp.