A crop loss model and economic thresholds for the grain aphid, Sitobion avenae (F.), in winter wheat in southern Sweden

The proposed crop loss model is a logistic curve: y=0.3826 ln(x)−0.4108 ( p<0.001; r2=0.9799; DF=7) similar to a classic inverted S-shape with no damage under 4 aphids/ tiller. The model shows rapidly increasing damage from 4 to10 aphids/straw but much less damage/aphid at aphid levels from 15 to 40 aphids/tiller. Dynamic economic thresholds are proposed for different expected yield levels and different growth stages. Thus the economic threshold for high yielding wheat is 1 aphid/tiller at crop stage 59, 4 at crop stage 69 and 7 at crop stage 75. Economic injury levels and economic thresholds are important components of a cost-effective integrated pest management programme and are useful for decision-making in the application of pesticides. Understanding and appropriate use of economic decision levels in dealing with pests can increase profits and maintain environmental quality.