Associations between weather factors and the spring migration of the damson‐hop aphid, Phorodon humuli

SUMMARY The dates of the beginning and end of the spring migration of P. humuli, as monitored by the Rothamsted Insect Survey suction traps at Wye College and Rosemaund Experimental Husbandry Farm, were linearly regressed on temperature, rainfall and sunshine for varying periods. The beginning of migration at both sites was associated with temperature in late March and early April, and periods of rainfall in mid-January and mid-April, while the end of migration was associated with temperature and sunshine in mid- and late June, and with mid-January rainfall. These regression equations were used to predict the timing of the migration in 1980 and 1981, those for mean maximum temperature predicting most accurately both the beginning and end of migration. The use of multiple regression equations did not increase the accuracy of predictions. The critical periods of weather are discussed in the context of the life-cycle of the aphid.