Validation of a sampling method: using one square centimeter for sampling the immature stages of Bemisia tabaci in soybean
2022
Weber, Igor Daniel | Czepak, Cecilia | Albernaz‐Godinho, Karina Cordeiro | Borges, Kevyllen Moreira Barbosa | Coelho, Alexandre Siqueira Guedes
Recently, a sampling method was proposed to estimate the population of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in soybean, Glycine max (L.) Merr. (Fabaceae), by counting its immature stages on 1 cm² leaf surface as a sampling unit to reduce the effort required. However, no study has verified whether this sampling unit could accurately estimate the immature stages similar to counting individuals in the total area of a soybean leaflet. Thus, we studied the correlation between the counts performed in 1 cm² and those in the total area of a leaflet to validate the ‘squared centimeter’ method as a sampling unit for immature stages of the whitefly. The research was carried out in two commercial soybean crops during the 2018/2019 harvest in Brazil. Each sampling was conducted by four individuals at 12 random collection points in the field. A plant was divided into three parts: apical, middle, and lower thirds, where a trifoliate leaf was removed from each of these plant thirds. For the evaluation, the trifoliate leaf was divided into left, central, and right leaflets. The immature whitefly population on its abaxial face was evaluated using two methods: counting in 1 cm² and counting in the total area of the leaflet. The four stages of immature B. tabaci quantified and identified were egg, crawler, nymphal stage 1–4 (N1–N4), and pseudo‐pupa. Significant positive correlations were detected between the mean counts in 1 cm² and in the total area of the soybean leaflet for the four whitefly stages. However, the correlation was weak for the crawler stage. Therefore, this study elucidates that 1 cm² as sampling unit is suitable for estimating the population densities of eggs, N1–N4, and pseudo‐pupa stages of B. tabaci in soybean plants.
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