Bellis Brothers Farm Report Final - December 2024
Testing a novel Alyssum-Orius ‘trap and kill’ IPM strategy for the control of thrips in Welsh 60-day strawberry crops
Bellis Brothers Farm in Holt, Wrexham, have been operating a strawberry pick-your-own (PYO) enterprise since 1967. In addition to other soft fruit production, the horticulture venture is supported by a successful garden centre and restaurant which helps attract business to the pick-your-own enterprise.
One of the main challenges with strawberry production at scale is pest and disease management. Thrips are one of the most significant pests affecting 60-day strawberry crops, potentially leading to serious fruit damage and crop losses. Until recently the main thrips species on UK strawberry crops has been western flower thrips (Figure 1), but other native species have been increasingly confirmed as causing damage. The damage caused includes discoloration and bronzing of the fruit (Figure 1) which reduces market quality and saleability. Even when chemical controls are applied, Bellis Brothers Farm experience an average loss of 5-10% of its outdoor-grown strawberry fruit to thrips in any given year. In 2021, the farm lost a crop worth £23,000 due to thrip damage and were therefore keen to find a solution to minimise future loss.
Figure 1: Western Flower Thrips © Nigel Cattlin/FLPA (left) Bronzing damage from thrips (right)
For this Try Out Fund project, grower and Farm Manager Adrian Marks worked alongside consultants at ADAS to trial a new approach to reduce thrip damage on the farm's pick-your-own strawberry crop.
Most strawberry crops in Wales are outdoor, 60-day PYO crops rather than everbearer polytunnel crops, more common in other parts of the UK. The plants are called 60-day strawberries, indicating that a crop of strawberries will be ready for picking 60 days after planting. At Bellis’ the strawberries are grown in a table-top production system where the plants are transplanted into growbags raised off the ground. The table-top system is beneficial due to built-in irrigation and eliminating the need for crop rotation.
Control of thrips in Welsh 60-day strawberry crops currently relies predominantly upon targeted sprays of the insecticide spinosad (Tracer®). However, this approach is not sustainable as many western flower thrip populations are resistant to spinosad, with the risk of other thrips species developing resistance. In addition, farmers and growers would prefer to reduce their reliance on pesticides and are therefore looking for alternative solutions.
Integrated Pest Management (IPM) is an approach that uses biological, cultural and physical methods, to prevent and control pests, disease and weeds in a more sustainable way, only resorting to chemical control as a last resort.
For this project the farmer and consultant trialled a biological control method in the form of the predator bug, Orius, and the flowering plant, Alyssum, to act as a trap for the pest, the Western Flower Thrip. The Orius are released onto the flowering Alyssum, which is then planted as a companion crop with the strawberry plants (Figure 2). With its high pollen count, flowering Alyssum attracts the thrips away from the strawberry plants, leaving the predator to feed on the pest.
Figure 2: Flowering Alyssum planted alongside strawberry during trial
Purpose of work
The primary aim of this project was to test a novel Alyssum-Orius ‘trap and kill’ IPM strategy for biological control of thrips, in outdoor 60-day strawberry crops. Questions the trial aimed to answer were:
- Can flowering Alyssum act as a trap plant for thrips, and a banker plant for Orius in 60-day strawberry crops?
- Can release of Orius to the Alyssum plants control thrips on the trap plants?
- Can biological control of thrips on the trap plants prevent them building up on the strawberry plants and causing fruit damage, thus avoiding the need for chemical thrips control?
What we did:
The peak period for thrip activity on strawberry crops is between May to July, during planting, flowering and fruiting.The 60-day strawberry variety used in this trial was ‘Malling Centenary’ which is very susceptible to thrips damage. The Alyssum variety was ‘Clear Crystal’, a large variety producing many flowers over a long flowering period.
In April 2024 during the pre-trial period, Alyssum plants were populated with the Orius families in a controlled environment at the nursery facilities at ADAS Boxworth. This was to establish the predator species on the trap crop before transporting to the farm and planting with the strawberry plants. The pre-trial assessment recorded the number of flowers on the Alyssum as well as the number of Orius adults and Orius nymphs (young). Other conditions were recorded including polytunnel temperatures during the inoculation period.
On 16th May 2024, the Alyssum plants were transported to the trial site and planted in grow bags at the same time as the table-top strawberry crop. The irrigation drippers were placed in the bags of Alyssum plants in the same way as they were placed in the strawberry bags, so that the Alyssum received the same water and liquid feed as the strawberry plants.
Figure 3: Aerial view of trial site
There were two treatments as part of the trial:
1) Flowering Alyssum interplanted with the strawberry plants
2) Control – the host grower’s standard commercial practice i.e., no biological control agents for thrips, application of spinosad (Tracer®) if thrips numbers indicated this was necessary.
There were eight replicate plots for each of the Alyssum treatment and the control. Treatment 1 (Alyssum) plots were located in Block 4, as far away as possible from Treatment 2 (control) plots in Block 3 (Figure 3). This was to reduce the risk of Orius adults flying into the control plots. There were 20 rows of table-tops in each of Blocks 3 and 4. Each row was 37m long.
There were two on-farm trial assessments, one during the strawberry flowering period in June, and a second trial assessment during the strawberry fruiting period in July.
Outcomes:
Due to an extended period of warm, dry weather in which thrips thrive, the farmer had detected an increasing number of the pests on the crop. With concerns of losing the crop, and after speaking with the consultants, the farmer opted to apply an emergency application of spinosad two days before the first assessment was due to take place.
Figure 4: ADAS Entomologist Jude Bennison examining strawberry flowers for thrips and Orius
The first assessment went ahead despite the change in circumstances (Figure 4). Unfortunately the application of spinosad had mostly eradicated the pest and the predator, making it impossible to test the establishment of Orius in the strawberry crop or its subsequent control of thrips in this trial. No Orius adults or nymphs were recorded in either the strawberry or Alyssum flowers. However, the grower reported that prior to the Tracer® spray, Orius had been easily observed in the strawberry flowers in the plots with flowering Alyssum.
If you would like to receive a copy of the technical report for this project please contact timtechnegolcff@menterabusnes.co.uk