title: Spatially-Optimized Sequential Sampling Plan for Cabbage Aphids Brevicoryne brassicae L. (Hemiptera: Aphididae) in Canola Fields.
abstract: The cabbage aphid is a significant pest worldwide in brassica crops, including canola. This pest has shown considerable ability to develop resistance to insecticides, so these should only be applied on a "when and where needed" basis. Thus, optimized sampling plans to accurately assess cabbage aphid densities are critically important to determine the potential need for pesticide applications. In this study, we developed a spatially optimized binomial sequential sampling plan for cabbage aphids in canola fields. Based on five sampled canola fields, sampling plans were developed using 0.1, 0.2, and 0.3 proportions of plants infested as action thresholds. Average sample numbers required to make a decision ranged from 10 to 25 plants. Decreasing acceptable error from 10 to 5% was not considered practically feasible, as it substantially increased the number of samples required to reach a decision. We determined the relationship between the proportions of canola plants infested and cabbage aphid densities per plant, and proposed a spatially optimized sequential sampling plan for cabbage aphids in canola fields, in which spatial features (i.e., edge effects) and optimization of sampling effort (i.e., sequential sampling) are combined. Two forms of stratification were performed to reduce spatial variability caused by edge effects and large field sizes. Spatially optimized sampling, starting at the edge of fields, reduced spatial variability and therefore increased the accuracy of infested plant density estimates. The proposed spatially optimized sampling plan may be used to spatially target insecticide applications, resulting in cost savings, insecticide resistance mitigation, conservation of natural enemies, and reduced environmental impact.
authors.affiliation: School of Animal Biology and The UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia Department of Agriculture and Food Western Australia, 3 Baron-Hay Court, South Perth, Western Australia 6151, Australia dustin.severtson@research.uwa.edu.au.
authors.forename: Dustin
authors.initials: D
authors.lastname: Severtson
authors.affiliation: School of Plant Biology and The UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
authors.forename: Ken
authors.initials: K
authors.lastname: Flower
authors.affiliation: Department of Entomology and Nematology, UC Davis, Briggs Hall, Davis, California, USA, and State Key Laboratory Breeding Base for Zeijang Sustainable Pest and Disease Control, Zeijang Academy of Agricultural Sciences, 198 Shiqiao Road, Hangzhou 310021, China.
authors.forename: Christian
authors.initials: C
authors.lastname: Nansen
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology*; D001937:Brassica / Q000254:growth & development; D007300:Insect Control / Q000379:methods*; D011156:Population Density; D012621:Seasons; D014904:Western Australia
keywords: IPM; crop scouting; edge effect; resampling software; spatial distribution