Estimating the population size of Steneotarsonemus concavuscutum in coconut fruits using diagrammatic damage scales

Abstract

Predictive models based on diagrammatic scales of damage have been developed to estimate the population density of Aceria guerreronis, an important coconut pest. Steneotarsonemus concavuscutum colonizes the same habitat as A. guerreronis and causes similar lesions on fruits. The present study aims to evaluate the possibility of using predictive models developed for A. guerreronis to estimate S. concavuscutum populations. Fruits infested by S. concavuscutum were collected and evaluated according to the diagrammatic scales developed by Galvão et al. (2008) and by Sousa et al. (2017). All active forms of S. concavuscutum were accounted for. Graphical and statistical analyzes were performed to evaluate the adequacy of the predictive models. Both the models proved to be inadequate to estimate the population of S. concavuscutum, both statistically and graphically. New predictive models were proposed using the grades of the diagrammatic scales and the mean numbers of S. concavuscutum/fruit. To validate the models, new fruits were collected and evaluated by 10 examiners with both the diagrammatic scales. All active forms of S. concavuscutum were accounted for. The new predictive model based on the grades of Galvão et al. (2008) underestimated the populations of S. concavuscutum, while the model obtained from the grades of Sousa et al. (2017) generated values close to the expected, proving itself to be adequate statistically and graphically, to estimate the populations of S. concavuscutum.

Acarofauna associated with coconut fruits (Cocos nucifera L.) in a crop area from Pará state, Amazon, Brazil

“…2017). Damage caused by tarsonemids can make identification difficult when they occur on the same fruit (França-Beltrão et al . 2022).…”

“…To compensate for this, França-Beltrão et al . (2022) suggested a new statistical model estimate populations of tarsonemids, which is based on the scale of notes proposed by Sousa et al . (2017) to estimate the population of A. guerreronis .…”

“…The simultaneous presence of several species of herbivores can affect the attractiveness of plants to the natural enemies of one species and reduce the natural enemy's performance (Lima et al 2017). Damage caused by tarsonemids can make identification difficult when they occur on the same fruit (França-Beltrão et al 2022)…”

“…Due to the similarity in damage, many producers tend to attribute damage only to A. guerreronis (Navia et al 2005;França-Beltrão et al 2018. According to França-Beltrão et al (2022), negative phototropism, small size, and large populations make it difficult to estimate the mites that occur in the perianth of coconut fruits, suggesting a new statistical model to estimate the populations of tarsonemids in fruit coconuts, which is based on the rating scale proposed by Sousa et al (2017) to estimate the population of A. guerreronis.…”

“…. To compensate for this,França- Beltrão et al (2022) suggested a new statistical model estimate populations of tarsonemids, which is based on the scale of notes proposed bySousa et al (2017) to estimate the population of A. guerreronis. Number of coconut fruits from bunches 13 to 17 with the presence of Aceria guerreronis and Steneotarsonemus furcatus in a coconut crop, from October 2019 to September 2020, at Pará state, Amazon, Brazil.…”