Raoiella indica Hirst (Acari: Tenuipalpidae) is a pest species that has expanded not only in geographical distribution but also in the number of host plants. Control measures are still being evaluated in recently invaded countries. In some countries and for some crops, spraying with botanical extracts has been used to reduce R. indica populations. Laboratory and field studies point to the predatory mite Amblyseius largoensis (Muma) (Acari: Phytoseiidae) as promising for combating R. indica. However, this predator has not yet been commercially available. Thus, the present study aimed to evaluate the potential of another predatory mite Neoseiulus barkeri Hughes, a commercially available generalist predator as a biological control agent of R. indica. The consumption and oviposition rate of N. barkeri were determined across the developmental stages of R. indica. The predation and oviposition capacity of N. barkeri and A. largoensis when fed R. indica eggs in the laboratory were compared. In the field, releases of the predator N. barkeri at densities of 900, 600 and 300 predators per plant were compared to spraying with botanical extracts such as cottonseed oil and azadirachtin to control R. indica. Our results suggested that N. barkeri is an effective predator to control R. indica. The consumption of N. barkeri was inversely related to the life stage of R. indica, and all developmental stages of R. indica enabled the reproduction of N. barkeri. The predation and oviposition of N. barkeri were higher than those of A. largoensis, and the releases of N. barkeri at densities of 900 and 600 predators/plant resulted in significant reductions in R. indica populations.
The giant whitefly, Aleurodicus cocois, is one of the main pests of cashew trees around the world. In the present study we evaluated the biological potential of the predaceous mites Amblyseius largoensis and Euseius concordis against A. cocois. The consumption and functional responses to prey egg densities of A. largoensis and E. concordis were investigated in laboratory experiments. Logistic regression indicated that both predators exhibited a type II response to prey eggs, and the eggs consumption increased with egg density up to a maximum, after which it slowly decreased. The value of the attack rate (a') was higher for A. largoensis than that for E. concordis, but the handling time (Th) did not differ between the two predators. The predicted maximum daily consumption was 35 eggs for A. largoensis and 32 eggs for E. concordis. Our results indicate that A. largoensis and E. concordis could be effective biocontrol agents of the cashew tree giant whitefly, especially in conditions of low pest population density.
My appreciations go out to all the people who intervened directly or indirectly in carrying out this work, especially to my place of work and to carry out this dissertation.To my supervisor, Dr. Aldo Barreiro for his full-time availability, for the continuous support at all stages and for the teaching transmitted during this work. For the internal course on the statistical R program, for the passed-on knowledge and for the patience with which he helped me in the doubts and errors that appeared during the work.To the people of the LEGE team, in the person of Professor Doctor Vítor Vasconcelos, for the welcome, the availability of help, advice, shared moments and the good working environment provided. Also to my co-worker and under the guidance, José Quaresma from
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