Survey and spatial distribution of tarsonemids and associated predators on coconut fruits

Abstract

Tarsonemids are mites that can damage coconut fruits, leading to losses in crop yield and quality. In this study, a survey of tarsonemid species and associated predatory mites underneath the perianth of coconut was carried out on palms cultivated along the coast of northeastern Brazil, and their spatial distribution was studied in one of the cultivations, on fruits of different ages, to subsidize monitoring and management of pest species. Samples of fruits of different ages were collected from cultivation sites of 9 states, with sites ranging from a few km to a maximum of 100 km apart from one another. Three coconut palms were selected from each site, collecting 10 fruits with necrotic lesions similar to those caused by Steneotarsonemus species from each palm. The mites were collected, mounted and identified. For the analysis, a re-evaluation was done of the tarsonemids collected in similar surveys for mites in general on coconut fruits, as reported previously in the literature. Subsequently, a field in Igarassu (Pernambuco, Brazil) bearing fruits with symptoms caused by Steneotarsonemus species was selected, and a total of 943 fruits from 2-8-month-old bunches were collected for mite quantification and identification. Consequently, Steneotarsonemus concavuscutum Lofego and Gondim Jr., Steneotarsonemus furcatus De Leon, and four morphospecies of Tarsonemus were found under the perianths of coconut fruits growing along the coast of northeastern Brazil. In Igarassu, the most abundant tarsonemid was S. concavuscutum, representing 98.4% of all quantified mites. Populations of S. concavuscutum were observed in all fruit bunches, regardless of age (ranging from 19 to 167 mites/fruit), with the highest numbers occurring in the 6-month-old bunches. In this same geographic location, Neoseiulus baraki (Athias-Henriot) represented 99.0% of the predaceous phytoseiid mites, with a population ranging from 0.04 to 5.3 mites/fruit that attained the highest population levels on 7-month-old fruit bunches. The N. baraki population densities were positively correlated with the mean S. concavuscutum numbers.