Population dynamics of Steneotarsonemus concavuscutum, a neglected mite pest in coconut fruits (Cocos nucifera).

The meristematic region of Cocos nucifera fruits can be colonized by various species of mites, including Steneotarsonemus concavuscutum, Steneotarsonemus furcatus, and Aceria guerreronis. The consequence of this colonization is the development of necrotic lesions on the fruit, and sometimes its abortion. Losses are commonly attributed to A. guerreronis alone, owing to the similarities in the injuries caused and its predominance in coconut plantations. However, S. concavuscutum may be the predominant pest species in some crops. Despite the possible impact of S. concavuscutum, little is known about its bioecological aspects, such as the influence of biotic and abiotic factors on its population dynamics. Our objective was to document macroclimatic abiotic factors (temperature, relative humidity, and precipitation) and biotic factors (interspecific competition and predation) interfere in the population dynamics of S. concavuscutum. We evaluated the diversity and abundance of mites in the perianth of coconut fruit naturally infested by S. concavuscutum for 1 year. The species found in the fruits of bunch 6 of the plant, which is the fruit age at which the mites commonly reach the highest abundance, were counted every 2 weeks. We found mites from nine families and S. concavuscutum was the predominant species, representing about 92% of the individuals collected. Predators represented approximately 2% of the total collection, with Neoseiulus baraki as the predominant species. Steneotarsonemus concavuscutum population density ranged from 60 to 397 mites/fruit. The highest population densities of S. concavuscutum were observed in the hottest and driest periods of the year. The population densities of S. concavuscutum were negatively associated with the presence of N. baraki, suggesting that this predator may have a role in the biological control of this pest.

Reinstatement of Metatarsonemus Attiah (Acari: Tarsonemidae), with description of a new species, redefinition of the genus and a key to the world species.

A new species, Metatarsonemus caissara Lofego Cavalcante sp. nov., is described based on females and males collected on Eugenia umbelliflora O. Berg. (Myrtaceae) from Atlantic Forest areas of São Paulo State, Brazil. Metatarsonemus Attiah is reinstated as a genus based on apomorphic attributes which are recovered through examination of specimens of the new species herein described, in addition to specimens of M. simplicissimus Attiah and M. megasolenidii Lofego Ochoa. A cladistic analysis tentatively indicates that the Metatarsonemus lineage is sister group to a lineage comprising the genera complex Daidalotarsonemus+Ceratotarsonemus+Excelsotarsonemus in sharing four homoplasious apomorphic attributes. A dichotomous key is provided for identification of the species of this genus described so far.