Sequential sampling plan for the adults of Conotrachelus psidii (Marshall, 1922) (Coleoptera: Curculionidae) in guava crop

Abstract

Understanding the spatial distribution and population fluctuations of insect pests facilitates the development of effective control strategies for a given crop. Conotrachelus psidii (Coleoptera: Curculionidae) is an important guava pest; however, no sampling plans are available for its management. Therefore, in this study, we aimed to (i) determine the spatial distribution pattern of C. psidii adults and (ii) develop a sequential sampling plan for pest control in guava crops. Evaluations began at 120 days after pruning and were performed weekly. To sample C. psidii adults, a white tarp was placed under the plants, covering the entire canopy. Plant branches were then shaken to dislodge the adult insects on the tarp, which were then identified and counted. Using the data obtained in each sampling, dispersion indices were determined and tests of adjustments to the theoretical Poisson and negative binomial frequency distributions were performed. The calculated dispersion indices revealed that the individuals in the studied populations exhibited aggregated dispersion. Notably, only four samples showed adjustment to the Poisson distribution, whereas 18 samples showed adjustment to the negative binomial distribution in the field, confirming the aggregated pattern of the population spatial arrangement. The sequential sampling plan developed for C. psidii revealed the maximum and minimum numbers of sample units expected for decision-making as 45 and 15, respectively.