Development of a sex pheromone monitoring trap for gooseberry sawfly

In 2013, excellent progress was made by EMR and NRI in identifying the sex pheromone of the blackcurrant sawfly, Nematus olfaciens (Tenthredinidae) (in HortLINK project HL01105). Pheromone blends have been tested in a trap designed for the pest and have shown significant catches of male sawfly. The studies have considerably advanced our understanding of the rather complicated sex pheromones of this family of insects and given us valuable expertise in the methods of identifying them. This finding will help the discovery of other closely related sawfly pheromones including the common gooseberry sawfly, Nematus ribesii which is a key insect pest of gooseberry. This species causes significant and devastating damage to gooseberry crops. The larvae devour large sections of the leaf lamina, often leading to complete bush defoliation. Damage often occurs in the centre of the bush first, but larvae soon disperse to feed on leaves throughout the whole plant. In addition, feeding attacks are often sporadic and unpredictable.

Predicting an outbreak is done by scouting for eggs, but this is time consuming and eggs may be missed if the plantation is not well covered during an inspection. The identification of the gooseberry sawfly sex pheromone would allow growers to predict adult emergence in the crop accurately and time and target plant protection products better to control adults and larvae feeding on the foliage.

Since 1987, the HDC has funded one project on gooseberry for one year. No projects have been funded on gooseberry pests. In addition, the chemical ecologist researching the blackcurrant sawfly pheromone is near to retirement and so now would be the ideal time to discover and exploit these key pheromones for monitoring in the field.

‘Now that the blackcurrant project appears to be bearing fruit, it would be the ideal time to extend the work to try and crack the gooseberry sawfly pheromone. As a gooseberry grower of a range of varieties, at the moment, I tend to spray whole plantations at a "suspected" timing of sawfly egg hatch. Of course I should be carefully crop walking to find eggs, but I know from bitter experience that sawfly hide in corners of plantations and generally stay well hidden. A trap to monitor the pest would be a godsend. To know, firstly, if the pest is about, then the timing of the flight so I can use the pesticides, if needed, accurately.’
William Hebditch, New Cross Fruit Farm, South Petherton, Somerset

‘A pheromone trap for gooseberry sawfly is an excellent idea with it being a pest that can have several generations in any year depending on the weather conditions. Having something that we can use to give us a clue to time pesticides applications, rather than waiting until we have damage because we missed seeing the caterpillars would give advantages, e.g. reduced wastage from mistimed sprays. There is the public perception of the industry. We need to show that we, as an industry, are doing our best to keep pesticide applications to a minimum.’
Les Winsor, Hillside Farm, Chapel Lane, Willington, Tarporley, Cheshire

(i) Project aim(s):

To develop a monitoring trap for gooseberry sawfly for use by growers to target sprays

(ii) Project objective(s):

• Detect and collect female-specific compounds released by female gooseberry sawfly which are likely to be components of the sex pheromone
• Explore the chemical structures of these compounds and synthesise if they can be identified
• Formulate candidate pheromone components in slow-release devices
• Test candidate pheromone components for attraction of male gooseberry sawfly and, if successful, begin calibrating the traps for field use
Progress on achieving these objectives will depend upon factors such as the amount of pheromone components produced by female gooseberry sawfly and the complexity of the chemical structures. In addition, subsequent objectives rely on the success of the preceding objectives. However, as the blackcurrant sawfly pheromone compounds have been identified we feel these risks would be relatively low, unless the pheromone is completely different.