Development of a Pheromone Trap for Monitoring Blackcurrant Sawfly

Summary

Summary: Blackcurrant sawfly, Nematus olfaciens (Diptera: Tenthredinidae), is a common and frequently damaging pest of blackcurrant, present to varying degrees in all UK blackcurrant plantations. Infestation is sporadic and localised, and damage can occur rapidly. No practical systematic sampling methods or attendant crop damage thresholds have been developed and it is believed that there is widespread unnecessary treatment with insecticides leading to the risk of residues remaining in the crop. Adequate crop scouting is time-consuming and expensive, and a more sensitive and rapid monitoring method is needed. Pheromone traps could provide such a tool.

In a previous Hort LINK project (Developing biocontrol methods and their integration in sustainable pest and disease management in blackcurrant production: HL01105), four potential components of the female sex pheromone of blackcurrant sawfly were identified and synthesised. Field tests suggested that three of these compounds were necessary for attraction of males. High catches of males were obtained in some fields and very low in others, confirming the sporadic nature of the pest.

This project will aim to optimise the pheromone blend, dispenser and trap and then to calibrate catches in the traps with field populations of blackcurrant sawfly. Factors affecting this relationship, such as the presence of predators and use of pesticides, will be investigated and thresholds for the two generations estimated. The trap will be made commercially available with a protocol for its use by growers.

Benefits to industry:

Blackcurrant sawfly is a common and frequently damaging pest of blackcurrant, present to varying degrees in all UK blackcurrant plantations. Larvae feed on foliage causing defoliation which weakens the bushes and causes substantial losses in yield. Larvae may also contaminate harvested fruit so good control prior to harvest is important. Infestation is sporadic and localised and damage can occur rapidly. Frequent crop inspection is needed for first signs of eggs, larvae and damage. Current grower practice is application of a spray of insecticide as soon as eggs, larvae or damage is detected by crop scouting and it is believed there is widespread unnecessary treatment leading to risk of residues in the crop.

Chlorpyrifos and thiacloprid are both very effective against sawfly but their future may be uncertain. Consumers’ desire for minimal, if not zero, residues of organophosphate materials is likely to limit or curtail the use of chlorpyrifos in the future.

Adequate crop scouting is time-consuming and expensive, and a more sensitive and rapid monitoring method is needed. More effective monitoring would help to make more cost-effective use of insecticides currently available with a likely reduction in their use. Monitoring will be vital for effective use of any more benign, biological approaches developed in the future. Pheromone traps could provide such a tool. Growers are generally familiar with this technology providing it is made readily available through commercial suppliers with adequate supporting information and protocols.

Sector:

Horticulture

Project code:

SF 162

Date:

01 March 2015 - 31 March 2018

Funders:

AHDB Horticulture

AHDB sector cost:

£80,740

Project leader:

MICHELLE FOUNTAIN, EAST MALLING RESEARCH

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About this project

Project aim:

The aim of the project is to develop a pheromone-baited trap for blackcurrant sawfly that can be used by growers to monitor populations so they can improve the timeliness and effectiveness of control measures and minimise insecticide residues in the crop.

Project objectives:

• Optimise pheromone blend, dispenser and trap for blackcurrant sawfly
• Calibrate catches in the pheromone trap with field populations of blackcurrant sawfly in two generations (over 2 years) and determine factors (pesticides and natural predation) affecting this relationship
• Make trap commercially available with protocol for its use by growers including suggested thresholds for the two generations