Sampling plans for aphids and their parasitoids in blueberry fields in Argentina

Abstract

Densities of aphids (Aphis gossypii and A. spiraecola) and mummified aphids at different phenological stages of a blueberry crop were estimated for the purpose of developing sampling plans. Our data set comprised 99 samples taken during the period 2006-2008 in four fields in Buenos Aires Province, Argentina. Estimation of population density based on the proportion of sample units infested by individuals was investigated. We also calculated the minimum number of sample units to estimate the density of individuals on buds and buds þ flowers using enumerative sampling. The relative precision of both methods was compared. Moreover, an enumerative sequential sampling protocol was developed. The presence-absence sampling plan gave density estimates with large variances (as measured by confidence intervals and large standard errors). The aggregation of mummies was similar on buds and buds þ flowers, so the required number of sample units for density estimates was the same. Relative precision of estimates was much lower for the presence-absence sampling than the enumerative sampling, even at intermediate densities. An enumerative sequential plan would be the most appropriate and useful method in management plans for aphids and mummified aphids in blueberries.

A binomial sampling method for estimating the density of blueberry aphid, Ericaphis fimbriata (Hemiptera: Aphididae), in commercial highbush blueberry

“…The applicability of these tools across different growing regions and different pest-crop systems is therefore not guaranteed. For example, let us consider the work of Rocca and Grecco (2012) on A. gossypii and A. spiraecola in highbush blueberry in Argentina. Their study develops a series of empirical models that estimate the density/proportion relationships of aphids or aphid mummies when sampling only vegetative tips or vegetative tips and flowers using the same distribution-free equation from Gerrard and Chiang (1970).…”

“…Binomial sampling is a common alternative method for estimating aphid density in a variety of crops (Hodgson et al 2004; Hummel et al 2004; Stokes et al 2013; Lara and Hoddle 2015; Lindenmayer et al 2020). In one study from Argentina, a binomial sampling plan was developed for the aphids, Aphis gossypii Glover and Aphis spiraecola Patch, in highbush blueberry (Rocca and Grecco 2012). In a binomial sampling scheme, the presence:absence of aphids on a sampling unit – e.g., a growing tip or an entire plant – is used as a proxy measure for the density of aphids within the sample environment.…”