British soft fruit growers tackle Western Flower Thrips
Four years of large scale trials combining the application of natural enemies (mainly the predatory mite Neoseiulus cucumeris) and Optiroll (Special blue sticky rolls from Russell IPM) have proved effective in bringing Western Flower Thrips under control. The strategy has increased financial returns to strawberry growers with the added benefit of reducing pesticide use.
Grower comments
Simon Clark (Manor Farm) said “After taking part in farm trials testing the blue Optiroll from Russell IPM in 2012, I have used the traps routinely on everbearer strawberries. Using the rolls, in conjunction with programmed applications of N. cucumeris throughout the season, has resulted in no fruit being lost to WFT damage.”
Tim Busby (Littywood Farm) said “Combining predators with traps has been very successful in controlling thrips. We have had no crop loss due to thrips in newly planted fields and minimal loss at the end of the season on a replanted 2nd year field. The cost of the programme is less than one weeks’ loss of production.”
The thrips control strategy
Dr Clare Sampson, who has overseen the development and evaluation of the combined approach, commented: “Growers were losing entire crops to WFT. The combined use of predatory mites with Russell IPM blue sticky traps provides a robust control system, consistently giving better thrips control than either method alone, and much better control than chemical pesticides. Damage is caused by the active thrips stages, adults and larvae, feeding on strawberry flowers and fruit. The predatory mites feed on thrips larvae, while the traps catch adult thrips, so using both as a combined strategy gives the best protection against damage.”
The predatory mites, Neoseiulus cucumeris (Figure 1), are released regularly throughout flowering to maintain sufficient numbers in the crop. In separate large-scale field trials, the blue Optiroll traps reduced peak numbers of adult thrips per flower by 56% on average, but by as much as 78%. Fruit bronzing was reduced by a similar amount (Figure 2), and the resulting increase in Class 1 fruit (Figure 3) increased grower returns by over £2,000 per hectare (Sampson and Kirk, 2013). Traps are put in place at first flowering and replaced in early July, but are most effective when thrips adults are actively flying in warmer weather, from July to September. The combined effect of predators and traps has provided reliable control as long as growers are careful to use a compatible pesticide programme in order to preserve the predators.
Figure 1: Neoseiulus (Amblyseius) cucumeris *
Growers were concerned that the traps would catch beneficial species as well as thrips, but were pleased to find that the Optiroll blue traps, which are selectively attractive to western flower thrips, integrated well with the natural enemies being released in strawberries and that bumblebee pollination was not affected by the traps.
Figure 2. Strawberry fruit bronzing (numbers of seeds surrounded by bronzing*) in plots with and without blue Optiroll traps.
The work was undertaken in a collaborative Defra funded Hort LINK research project between growers, industry and research institutes to develop effective strategies to manage WFT. Richard Harnden (Berry Gardens) who chaired the project commented “Collaborative research and development projects pooling knowledge and resources of industry, research institutes and growers have demonstrated their value in developing relevant and practical solutions for growers and providing a good return on the investment. It is a win-win formula”.
Figure 3. Percentage of Class 1 and Class 2 fruit with and without blue Optiroll traps.
Russell IPM, a North Wales based manufacture of the Optiroll Blue is involved in a further research and development project engaging Dr Sampson and Keele University to further improve the performance of the sticky traps through the incorporation of visual stimulants and semiochemicals.
“We are pleased to see that our product is playing a key part in an integrated solution which can bring benefit to growers and we will continue to work together to bring more innovative and beneficial solutions to growers.” commented Dr Shakir Al-Zaidi, Managing Director of Russell IPM.
Reference: Sampson C, Kirk WDJ (2013) Can mass trapping reduce thrips damage and is it economically viable? Management of the western flower thrips in strawberry. PLOS ONE 8(11): 80787.
*Courtesy of Dr Mark Hoddle, Center for Invasive Species Research, UCRiverside.
For more information:
Russell IPM
Dr Shakir Al-Zaidi
Managing Director
+44 (0) 1244 281 333
info@russellipm.com