Reduced sampling frequency for evaluating fungicide efficacy on Botrytis fruit rot of strawberry

Evaluating fungicide efficacy in annual strawberry production systems can b e labor intensive due to continuous harvesting over a relatively long seaso n. The effect of reduced harvest number on the accuracy of least significan t difference (LSD) separations for Botrytis fruit rot (Botrytis cinerea) in cidence and marketable yield in fungicide efficacy studies was evaluated ov er three seasons. Fruit were harvested and graded twice a week for a total of 23 to 32 harvests each season. Data from each season were divided into d ifferent sample sets. Data from three different harvest periods (early, lat e, and whole season) and different harvesting frequencies (twice weekly, on ce weekly, every second, third, or fourth week) were compared with the comp lete data set (twice weekly for the whole season). Spearman's rank correlat ion and Pearson's product moment correlation coefficients were used to eval uate the correlation of the complete data sets with data sets from other sa mpling plans. Harvesting once a week for either the late- or whole-season p eriods accurately estimated LSD groupings for Botrytis fruit rot incidence among fungicide treatments. The precision of marketable yield estimates usi ng once-a-week harvesting for the late or whole-season periods were relativ ely lower than for the incidence of Botrytis.