Andreia Serra Galvão

Biologia de Amblyseius largoensis (Muma) (Acari: Phytoseiidae), um potencial predador de Aceria guerreronis Keifer (Acari: Eriophyidae) em coqueiro

Aceria guerreronis Keifer is considered one of the main pests of coconuts around the world. Amongst the Phytoseiidae recorded on this crop, Amblyseius largoensis (Muma) has been reported in association with A. guerreronis. In order to verify whether A. largoensis feeds on A. guerreronis, the biology of this predator was evaluated on different food sources, including A. guerreronis. Three types of diet were tested [Tetranychus urticae Koch + castor bean (Ricinus communis L.) pollen + honey at 10%, A. guerreronis + pollen + honey, and only A. guerreronis], determining its development, survivorship, oviposition, sex ratio and longevity at 27oC, 60 ± 5% RH 12 h photophase. Fertility life tables were constructed. The duration of the immature phase was lower when feeding only on A. guerreronis, while fecundity was higher when feeding on a prey + pollen + honey. There was no difference in relation to survivorship of the immature stages between the three diets. Parameters of fertility life tables were higher when the diet included A. guerreronis or T. urticae + pollen + honey, although the predator was able to complete its life cycle and reproduce when feeding exclusively on A. guerreronis. The results suggest that A. largoensis preys upon A. guerreronis under natural condition and that it might play some role in the control of the latter.

Dispersal strategies of Aceria guerreronis (Acari: Eriophyidae), a coconut pest

The dispersal of plant-feeding mites can occur involuntarily, through transportation of infested plant parts, or voluntarily, by walking to new plant parts or to suitable spots where biotic (phoresis) or abiotic (wind, agricultural tools, etc.) factors carry them over long distances. Elucidating the dispersal mechanisms of the coconut mite, Aceria guerreronis Keifer, is important for understanding the process of colonization of new fruits of a same or different plants, essential for the improvement of control strategies of this serious coconut pest. Thus, the objective of this work was to investigate the voluntary dispersal mechanisms of this mite. The hypothesis that the coconut mite disperses by walking, phoresis or wind were tested. The coconut mite was shown to be able to walk short distances between fruits of the same bunch or between bunches of the same plant. Phoresis on insects of the orders Hymenoptera (Apidae), Coleoptera (Curculionidae) and Lepidoptera (Phycitidae) was evaluated in the laboratory and in the field. Although in the laboratory mites were shown to be able to climb onto honeybees, field investigations failed to show these insects as important carriers of the pest, corroborating findings of previous works; however, both laboratory and field investigations suggested the curculionid Parisoschoenus obesulus Casey to be able to transport the coconut mite between plants. Similarly, laboratory and field investigations suggested wind to be important in the dispersal of the coconut mite between plants.

Escala diagramática de dano de Aceria guerreronis Keifer (Acari: Eriophyidae) em coqueiro

Aceria guerreronis Keifer e importante praga do coqueiro no mundo. Dada a falta de metodos padronizados para a quantificacao dos danos causados por esse eriofiideo, uma escala diagramatica com niveis de 1, 2, 4, 8, 16, 32, 48 e 70% de danos foi elaborada e testada para precisao e reprodutibilidade das estimativas. Para validar a escala, frutos com diferentes niveis de dano foram previamente avaliados com o programa Assess® e submetidos a avaliacao por 10 avaliadores inexperientes com e sem a escala (1a avaliacao) e sete dias apos (2a avaliacao) com os mesmos avaliadores, empregando-se as fotos digitalizadas dos mesmos frutos com sequencia diferente. A acuracia e a precisao de cada avaliador foram determinadas por regressao linear simples entre o dano observado e estimado. Sem a utilizacao da escala, sete de 10 avaliadores superestimaram o nivel de dano, sendo pouco precisos. No entanto, avaliadores utilizando a escala obtiveram melhores niveis de acuracia e precisao. Os avaliadores apresentaram niveis mais elevados de reprodutibilidade das estimativas com a utilizacao da escala comparada as avaliacoes sem a escala. A escala foi utilizada para determinar a relacao entre a infestacao e o dano causado por A. guerreronis. A relacao entre infestacao e niveis de dano apresentou elevada precisao (R2 = 99,87%, P < 0,0001) pela equacao lny = 4,948 - 0,121 x + 1,789 lnx. Portanto, os resultados comprovam que e possivel estimar a populacao de A. guerreronis nos frutos de coco infestados com a utilizacao da escala diagramatica.

Exigências térmicas e tabela de vida de fertilidade de Amblyseius largoensis

Amblyseius largoensis (Muma) (Acari: Phytoseiidae) is a species widely spread and naturally occurring in the tropics and subtropics regions. This species is also associated with perennial plants and considered an important predator of Aceria guerreronis Keifer (Acari: Eriophyidae) in coconut trees (Cocos nucifera L.). The objective of this research was to determinate the thermal requirements of A. largoensis fed with a combination of Tetranychus urticae Koch (Acari: Tetranychidae), pollen of Ricinus communis L. and a 10 % honey solution. The study was conducted at 18, 21, 24, 27 and 30°C, 70 ± 10 % relative humidity and 12 h photophase. At these temperatures, the period from egg-adult lasted 14.0, 8.6, 6.1, 5,0 e 3.9 respectively. At those temperatures, the threshold temperature for the development of larva, protonynph, deutonymph and egg-adult were 13.3, 13.3, 13.5, 11.9 and 13.3°C, and the thermal constants were 20.9, 13.5, 14.9, 18.9 and 66.1 degree-days, respectively. The fertility life table parameters were better in the 27 and 30°C.

Acute and non-lethal effects of coconut oil on predatory mite Typhlodromus ornatus (Acari: Phytoseiidae)

Abstract Typhlodromus (Anthoseius) ornatus Denmark & Muma (Acari: Phytoseiidae) is one of the predatory mites associated with the coconut mite Aceria guerreronis (Acari: Eriophyidae), a serious coconut pest in Africa, Asia and America. Vegetable oils such as coconut oil have been shown to efficiently control A. guerreronis, however their side effects on predatory mites remain poorly investigated. Here, we evaluated the lethal and non-lethal effects of coconut oil on repellence and functional response of the predatory mite T. ornatus, a natural enemy of A. guerreronis. Based on LC50 estimates, coconut oil was over 6-fold less toxic to T. ornatus than to its prey, A. guerreronis. Additional repellence and predation bioassays show that the coconut oil neither repels nor interferes in the functional response of T. ornatus preying upon A. guerreronis. According to our selectivity approach, the coconut oil is compatible with the predatory mite T. ornatus.