The UK grows about 6,000 ha of lettuce outdoors during the spring and summer months. Pest insects can cause major problems for salad growers both in terms of direct damage and as contaminants in marketed produce. The principal pests are aphids and caterpillars. A range of insecticides are available to control these pests and cultivars of lettuce resistant to the key pest aphid, Nasonovia ribisnigri, have been on the market for some time. In recent years, populations of N. ribisnigri which can overcome this form of host-plant resistance have been found in European lettuce crops, including the crops in the UK.
BIOLOGY AND CONTROL OF THE CURRANT-LETTUCE APHID (NASONOVIA RIBISNIGRI)
Gemma Hough’s HDC-funded PhD project has quantified aspects of the life cycle of the currant-lettuce aphid to inform development of a more effective and targeted control strategy. The project considered several aphid clones, some of which were able to overcome the host-plant resistance available currently in commercial cultivars.
IDENTIFYING NEW SOURCES OF RESISTANCE TO NASONOVIA RIBISNIGRI
A lettuce genetic diversity set consisting of 96 lines has been screened for susceptibility to N. ribisnigri as part of the Vegetable Genetic Improvement Network (VeGIN) project funded by Defra. The lines show a wide range of susceptibility, suggesting that there is the potential to identify new sources of resistance.
NOVEL INSECTICIDES AND BIOPESTICIDES
New insecticides and biopesticides are being tested as part of the LINK SCEPTRE project. Trials at Warwick Crop Centre on lettuce are targeting aphids and caterpillars.
FORECASTING PEST INFESTATIONS
• Forecasts for the pest aphids of lettuce
• ‘Real-time’ information from Rothamsted suction traps
• A forecast for cutworm (turnip moth)
• Trap data on silver Y moth and turnip moth
Silver Y moth
Turnip moth caterpillars (cutworm)