A comparison of precision and economic efficiency for three methods of thrips population density assessment.

Western flower thrips, Frankliniella occidentalis, is a major pest and vector in many parts of the world. Methods for assessing thrips population density for pest management decision support are often inaccurate and/or imprecise due to thrips’ positive thigmotaxis, small size, and naturally aggregated populations. Two established methods, flower tapping and an alcohol wash, were compared to a novel method, plant desiccation coupled with passive trapping, using precision and economic efficiency as comparative variables. Flower tapping was the least expensive method, in terms of man-hours, while the alcohol wash method was the most expensive. Precision, expressed by relative variation, depended on location within the greenhouse, location on greenhouse benches, and the sampling week, but was generally highest for the flower tapping and desiccation methods. Economic efficiency, expressed by relative net precision, was highest for the flower tapping method and lowest for the alcohol wash method. Advantages and disadvantages for all three methods are discussed. Additionally, the difference between accuracy and precision is discussed in terms of insect population density assessments, pest management and pesticide efficacy.