Feasible sampling plan for Bemisia tabaci control decision-making in watermelon fields.

BACKGROUND: The silverleaf whitefly Bemisia tabaci is one of the most important pests of watermelon fields worldwide. Conventional sampling plans are the starting point for the generation of decision-making systems of integrated pest management programs. The aim of this study was to determine a conventional sampling plan for B. tabaci in watermelon fields. RESULTS: The optimal leaf for B. tabaci adult sampling was the 6th most apical leaf. Direct counting was the best pest sampling technique. Crop pest densities fitted the negative binomial distribution and had a common aggregation parameter (Kcommon ). The sampling plan consisted of evaluating 103 samples per plot. This sampling plan was conducted for 56 min, costing US$ 2.22 per sampling and with a 10% maximum evaluation error. CONCLUSIONS: The sampling plan determined in this study can be adopted by farmers because it enables the adequate evaluation of B. tabaci populations in watermelon fields (10% maximum evaluation error) and is a low-cost (US$ 2.22 per sampling), fast (56 min per sampling) and feasible (because it may be used in a standardized way throughout the crop cycle) technique. © 2017 Society of Chemical Industry.

Economic injury levels and sequential sampling plans for Frankliniella schultzei in watermelon crops.

BACKGROUND: The thrips Frankliniella schultzei is an important watermelon pest. Nevertheless, economic injury levels and sampling plans for this pest have not yet been determined for this crop. Thus, the objective of the present study was to determine the economic injury levels and develop sequential sampling plans for F. schultzei in conditions of low, medium and high fruit prices. RESULTS: The attack of F. schultzei on watermelon plants at the vegetative stage reduced the crop's productivity, which did not happen at the flowering and fruiting stage. The economic injury levels were 0.09, 0.04 and 0.02 thrips leaf-1 when the watermelon price was low ($US 62.5 t-1 ), medium ($US 140.63 t-1 ) and high ($US 218.75 t-1 ) respectively. The three sequential sampling plans for F. schultzei generated for the economic injury levels resulted in similar and more rapid decisions compared with the conventional plan, especially when the pest density was high. CONCLUSIONS: The three economic injury levels and the sequential sampling plans generated in the present study can be incorporated into integrated pest management programmes for watermelon crops because these plans provide a rapid and adequate control decision for F. schultzei. © 2016 Society of Chemical Industry.