When will aphids fly this year? (aphid forecasts)

Long-term (59 years in 2023) aphid data (from the suction-trap network) and weather data (Met Office and others) is used to forecast the date of the first aphid flights, as well as aphid abundance in spring and early summer.

The best predictor of the timing and size of aphid migration is the mean temperature in January and February. Temperatures in November/December and March/April have little apparent impact.

Although there is considerable uncertainty associated with actual first flight dates at specific sites, the forecasts provide an indication of how early or late flights will take place, compared with an ‘average’ season.

Confidence is greatest for aphid species that pass the winter in the active stages (rather than as cold-hardy eggs in diapause), as they are more susceptible to low winter temperatures and can take advantage of warm conditions

• Bird cherry–oat aphid (Rhopalosiphum padi) and rose–grain aphid (Metopolophium dirhodum) overwinter by either method, with the proportion overwintering in the active stages increasing towards the south.
• The peach–potato aphid (Myzus persicae) and potato aphid (Macrosiphum euphorbiae) pass winter in the active stages.
• Grain aphid (Sitobion avenae) and mealy cabbage aphid (Brevicoryne brassicae) overwinter mainly in the active stages. However, as the latter flies later it is more difficult to predict. Therefore, for this species, the forecast also uses December temperatures.

Note: Some aphids overwinter in autumn-sown cereal crops and might present before aphid flight begins. The forecasts do not capture all variability. Interpret results with caution.

• The predicted date range of first capture, together with the position of this year's prediction out of all years of trap operation (e.g.16/52 = 16th earliest out of 52 years). Note: For actual capture information, visit the Rothamsted Research Insect Survey bulletin page.
• The predicted numbers caught by specified dates: Cereal aphids (1 July), peach–potato aphid and potato aphid (17 June) and cabbage aphid (7 October), together with the position of this year's prediction out of all years of trap operation.