Economic injury levels for the potato yellow vein disease and its vector, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), affecting potato crops in the Andes

Abstract

The Economic Injury Level (EIL) for pest insects is conventionally expressed in terms of the number of insects, because the level of pest injury to plants is usually difficult to quantify. However, when insect injury is mainly caused indirectly by transmission of plant pathogens, the number of insects may not be an ideal measure to calculate the EIL. The greenhouse whitefly (GWF) Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) is the only known vector of the Potato yellow vein virus (PYVV), the causal agent of potato yellow vein disease (PYVD), but the direct injury caused by insect feeding may not be significant since potato is not a preferred host for the GWF. Here, we quantified the effect of GWF feeding and PYVD incidence on potato yield, as compared to potato market value and control costs to determine the EIL for this system. We found that the direct injury caused by GWF feeding does not affect potato yield. However, an exponential reduction in crop yield was observed with the increase of PYVD incidence. Thus, the criteria to decide upon applying a control measure ranges between 100 and 1200 infected plants/ha depending mainly on potato market price. We suggest that disease incidence should be used to calculate the EIL for PYVD management, instead of focusing on estimations of vector population size. Furthermore, we stress that potato market price is fundamental in defining an appropriate, case specific EIL for decision-making in PYVD management.