Sequential sampling of the citrus leprosis mite in different cultivation systems in the Eastern Amazon

Citrus leprosis is a major viral disease transmitted by the citrus leprosis mite (Brevipalpus spp.), causing significant economic losses in Brazilian citrus farming. This study developed a sequential sampling plan for Brevipalpus spp. in two citrus cultivation systems. Two plots in an orange orchard ('Pêra Rio' variety) in Capitão Poço, Pará, Brazil, were selected: one under monoculture and the other intercropped with teak. Monthly sampling from September 2015 to August 2016 involved 112 georeferenced plants per plot. Mite counts were performed on six fruits, branches, and leaves from both inner and outer plant parts using a 10 × pocket lens. Aggregation indices, including variance-to-mean ratio, Morisita's index, Green's coefficient, and Taylor's power law, revealed an aggregated distribution for all variables. The k parameter of the negative binomial distribution confirmed aggregation, and this model provided the best fit for both systems. The sequential sampling plan determined that the maximum expected sampling units for decision-making is 21 mites per plant and 28 mites per six branches in both systems. These thresholds were established based on the observed distribution pattern and aim to enhance monitoring efficiency. Although these values may seem low, they indicate the infestation level at which control measures should be implemented to prevent economic losses. These findings contribute to improved monitoring strategies for Brevipalpus spp. in citrus orchards, supporting more effective pest management.