SPATIAL DISTRIBUTION AND SEQUENTIAL SAMPLING OF Brevipalpus phoenicis IN CITRUS

Abstract

ABSTRACT-Among the pests of citrus, one of the most important is the red and black flat mite Brevipalpus phoenicis (Geijskes), which transmits the Citrus leprosis virus C (CiLv-C). When a rational pest control plan is adopted, it is important to determine the correct timing for carrying out the control plan. Making this decision demands constant follow-up of the culture through periodic sampling where knowledge about the spatial distribution of the pest is a fundamental part to improve sampling and control decisions. The objective of this work was to study the spatial distribution pattern and build a sequential sampling plan for the pest. The data used were gathered from two blocks of valencia sweet orange on a farm in São Paulo State, Brazil, by 40 inspectors trained for the data collection. The following aggregation indices were calculated: variance/ mean ratio, Morisita index, Green's coefficient, and k parameter of the negative binomial distribution. The data were tested for fit with Poisson and negative binomial distributions using the chi-square goodness of fit test. The sequential sampling was developed using Wald's Sequential Probability Ratio Test and validated through simulations. We concluded that the spatial distribution of B. phoenicis is aggregated, its behavior best fitted to the negative binomial distribution and we built and validated a sequential sampling plan for control decision-making. Index terms: red and black flat mite, negative binomial, Poisson distribution, decision making, integrated pest management. DISTRIBUIÇÃO ESPACIAL E AMOSTRAGEM SEQUENCIAL DE Brevipalpus phoenicis EM CITRUSRESUMO-Dentre as pragas dos citros, uma das mais importantes é o ácaro da leprose Brevipalpus phoenicis (Geijskes), que transmite o vírus da leprose dos citros (CiLv-C). Quando um plano racional de controle de pragas é adotado, é importante se determinar o tempo correto para se dar início ao plano de controle. Para tanto, é necessário acompanhamento constante da cultura através de amostragens periódicas, onde o conhecimento do comportamento espacial da praga é fundamental. O objetivo deste trabalho foi estudar o padrão de distribuição espacial e desenvolver um plano de amostragem sequencial para a praga. Os dados utilizados foram coletados em dois talhões de laranja valência em uma fazenda no estado de São Paulo, Brasil, por 40 inspetores treinados para a atividade.

Spatio-temporal distribution, diversity and monitoring of fruit flies (Diptera, Tephritidae) in papaya orchards in the state of Espírito Santo, Brazil

“…In addition, the analysis taking into account the frequency distribution of the fruit flies confirmed the suitability of the negative binomial model for all scenarios analyzed (different periods: 1998 to 2003, 2004 to 2010, and different areas: full area, buffer zone, and neighborhoods 1 and 2). Insect count data are generally not distributed (Sileshi, 2006), and there is evidence showing that the frequency distribution in this taxonomic group is ecologically described by a negative binomial distribution Maldonado et al, 2016;Nicácio et al, 2019). This function characterized by variance significantly higher than the mean , was observed in our results.…”

Spatial patterns of the Citrus leprosis virus and its associated mite vector in systems without intervention

“…The aggregation pattern of trees with leprosis symptoms was common at the three levels of spatial hierarchy. This disease aggregation pattern has also been reported in previous studies using similar spatial analyses (Bassanezi & Laranjeira, ) or geostatistical analysis (Maldonado Junior et al ., ). Conversely, the spatial pattern of B. yothersi‐ infested trees (unknown infection status) was predominantly random in all levels of spatial hierarchy, where Z (BB) values were lower than those for trees with leprosis symptoms and random for the major lags.…”

“…In contrast, Bassanezi & Laranjeira () studied the pathosystem in groves with chemical management for mite control and without successive assessment of disease incidence and mite infestation over time. Other studies have focused either on spatial distribution of citrus leprosis (Oliveira Junior et al ., ) or on spatial distribution of the mite vector (Maldonado Junior et al ., ). Despite CiLV‐C dispersal being totally vector‐dependent, the spatial pattern of mite‐infested trees and trees with leprosis symptoms were not similar.…”

“…The autocorrelation spatial analysis of the mite‐infested trees spatial pattern was not consistent with the trees with leprosis symptoms spatial pattern. This finding is in contrast with results from other studies that have reported an aggregated spatial pattern of mite‐infested trees (Maldonado Junior et al ., ).…”

“…Alternative mite sampling strategies have been reported in previous studies to improve the disease control strategy, yet the CiLV-C spatial pattern has not been contemplated (Maldonado Junior et al, 2016). In sweet orange commercial groves, precise estimations of leprosis incidence are difficult to calculate and depend on specific sampling plans designed for a highly aggregated disease pattern.…”