Print version ISSN 0301-8059
An. Soc. Entomol. Bras. vol.29 no.3 Londrina Sept. 2000
Predatory activity of Phytoseiid mites on the developmental stages of coffee ringspot mite (Acari: Phytoseiidae: Tenuipalpidae)
Atividade predatória de ácaros Fitoseídeos sobre os estádios de desenvolvimento do ácaro da mancha-anular do cafeeiro (Acari: Phytoseiidae: Tenuipalpidae)
Paulo R. Reis; Adenir V. Teodoro; Marçal Pedro Neto
EPAMIG-CTSM, Caixa postal 176, 37200-000, Lavras, MG, Brasil
By means of bioassays performed in arenas of 3 cm in diameter, manufactured with coffee leaves floating on water, the phases of the coffee ringspot mite Brevipalpus phoenicis (Geijskes) were studies on the preference by several developmental stages of the predaceous mites Euseius alatus DeLeon and Iphiseiodes zuluagai Denmark & Muma. The experiment was conducted in laboratory at 25 ± 2ºC, 70 ± 10% RH and 14 h photophase. The preferred stage of coffee ringspot vector virus was the larva followed by nymph and egg. Adults were least preyed on. In general, the most aggressive phase of the predators was the adult female followed by the nymph; the larval phase was the least aggressive. The average predation of E. alatus and I. zuluagai for the different phases of B. phoenicis were, respectively: larva (79% and 90%) > egg (47% and 83%) > nymph (40% and 77%) > adult (1% and 18%). This result indicated that I. zuluagai is more aggressive than E. alatus in relation to its predation upon B. phoenicis.
Key words: Rhabdovirus, biological control, flat-mite, Brevipalpus phoenicis, Euseius alatus, Iphiseiodes zuluagai.
Através de bioensaios realizados em arenas com 3 cm de diâmetro, confeccionadas com folhas de cafeeiro flutuando em água, foram estudadas as fases do ácaro da mancha-anular do cafeeiro Brevipalpus phoenicis (Geijskes) quanto à preferência pelos diversos estádios do desenvolvimento dos ácaros predadores Euseius alatus DeLeon e Iphiseiodes zuluagai Denmark & Muma. Os experimentos foram conduzidos em laboratório a 25 ± 2ºC, 70 ± 10% de UR e 14 horas de fotofase. O estádio do ácaro vetor mais predado foi o de larva, seguido pelo de ninfa e ovo. A fase adulta teve muito pouca predação. De modo geral, a fase mais agressiva dos predadores foi a de fêmea adulta, seguida pela de ninfa. A fase de larva foi a menos eficiente na predação. As médias de predação de E. alatus e I. zuluagai para as diferentes fases do B. phoenicis foram respectivamente: larva (79% e 90%) > ovo (47% e 83%) > ninfa (40% e 77%) > adulto (1% e 18%), o que demonstra que I. zuluagai mostrou maior atividade predatória que E. alatus.
Palavras-chave: Rhabdovirus, controle biológico, ácaro-plano, Brevipalpus phoenicis, Euseius alatus, Iphiseiodes zuluagai.
The mite Brevipalpus phoenicis (Geijskes) has been reported on coffee trees in Brazil since 1951 (Anonymous 1951). More recently, it was related to coffee ringspot (Chagas 1973) caused by a virus of the Rhabdovirus group (Chagas 1988).
Coffee ringspot was not considered of any economic problem until 1988 (Chagas 1988). Since 1990, and specially in 1995, infestations by B. phoenicis and ringspot have been reported in the state of Minas Gerais causing intense leaf dropping on coffee trees, mainly in the region of Alto Paranaíba. The presence of the mite being also found in other coffee growing regions of Brazil, both in arabic (Coffea arabica L.) and canephora (Coffea canephora Pierre) coffee species.
The mite B. phoenicis is often found associated with the predaceous mites Iphiseiodes zuluagai Denmark & Muma and Euseius alatus DeLeon (Acari: Phytoseiidae), among others. Phytoseiids have been widely studied and considered the most effective predatory mites (McMurtry et al. 1970, Moraes 1991). Pallini Filho et al. (1992) reported a number of species of predator mites on coffee trees, among them, I. zuluagai and E. alatus, which were the object of this study. The consumption of prey by phytoseiid mites has been investigated chiefly for mites of the family Tetranychidae. Smith & Newsom (1970) showed that adult females of the phytoseiid Neoseiulus fallacis (Garmam) are the most efficient phase in relation to predation on Tetranychus urticae Koch (Acari: Tetranychidae), while other stages of the predator still contributed to the control of the pest. Using eggs of T. urticae as prey, Ma & Laing (1973) found that larvae of Neoseiulus chilenensis (Dosse) did not feed, and that the females were more efficient in predation than males, mainly during the oviposition period. Gravena et al. (1994) estimated the predatory activity of the phytoseiid Euseius citrifolius Denmark & Muma upon citrus leprosis mite, B. phoenicis, and found that larvae, nymphs and adult females were similar and or superior in the predatory activity than adult males.
Because the predatory mites I. zuluagai and E. alatus are found on coffee (Pallini Filho et al.1992) and citrus trees (Reis et al. 2000), on which B. phoenicis is also an important pest, this study was conducted to investigate the predatory activity of those predaceous mites on each developmental stage of B. phoenicis.
Material and Methods
The predation potential of the predaceous mites was studied through bioassays using arenas of 3 cm in diameter, made of healthy and unsprayed coffee leaves (C. arabica) floating in water. The study was conducted at the acarology laboratory of the Centro Regional de Pesquisa do Sul de Minas, of Empresa de Pesquisa Agropecuária de Minas Gerais - EPAMIG, in Lavras (MG), at 25 ± 2ºC, 70 ± 10% RH and photophase of 14 h (daylight lamp).
Five arenas were placed to float on water in open dishes petri 15 cm in diameter by 2 cm in depth. Each arena contained a central hole to fit the passage of a pin. The pins were fixed by the head to the bottom of the dish with silicone glue before adding the water, in such a way as to prevent touching each other or the walls of the dish. Water was added daily to prevent the arenas from touching the bottom, serving as a permanent barrier to prevent the mites from escaping (Reis et al. 1998).
Bioassays were performed using every possible combinations between each developmental phase of I. zuluagai and E. alatus (larva, nymph, male and female) and the prey B. phoenicis (egg, larva, nymph and adult female). A control was included, consisting of each prey phase without predator. Each combination and respective control had ten replications. Each arena received a predator and 20 prey at the desirable phases. After 24 hours of the introduction of the mites into the arena, the numbers of completely preyed, partially preyed, naturally dead, dead in water and living mites were counted. The mites, both predators and B. phoenicis, were obtained from maintenance rearing (Reis & Alves 1997b) which enabled the utilization of mites of uniform age.
Results and Discussion
Results obtained are shown on Table 1. Throughout the observation time, neither natural death nor death in water of the mite B. phoenicis was observed in the check treatment. Thus, no correction for predation was performed.
The phases of B. phoenicis consumed, in order of preference, by the larvae of the predator E. alatus were: larva (75%) > nymph (39%) > egg (14%) > adult (0%). By the nymphs were: larva (80%) > nymph (48%) > egg (21%) > adult (1%). By the females were: egg (91%) > larva (89%) > nymph (52%) > adult (2.5%). By the males of the predator were: larva (67%) > egg (28%) > nymph (19%) > adult (1%) (Fig. 1).
The phases of B. phoenicis consumed, in order of preference, by the larvae of I. zuluagai were: larva (29%) > nymph (11%) > egg (10%) > adult (1%). By the nymphs were: egg (92%) > larva (91 %) > nymph (76%) > adult (13%); by the females were: egg (99%) > nymph (99%) > larva (98.5%) > adult (35%). By the males of the predator were: larva (81%) > egg (59%) > nymph (55%) > adult (7%) (Fig. 2).
The average predation of nymphs, males and females of E. alatus and I. zuluagai for the different phases of B. phoenicis were, respectively: larva (79% and 90%) > egg (47% and 83%) > nymph (40% and 77%) > adult (1% and 18%), which showed greater predatory activity by I. zuluagai than E. alatus. For both predators, adult female was the most efficient phase in relation to consumption of all the developmental phases of B. phoenicis, mainly that of E. alatus. Similar results were obtained by Gravena et al. (1994) for E. citrifolius feeding on B. phoenicis. Smith & Newsom (1970) and Ma & Laing (1973) also found the greatest efficiency of females of phytoseiids as predators, in relation to the other developmental phases, with tetranychid mites as a prey.
The larval phase of the predators was the least efficient, perhaps because of their reduced size and the short duration of that stage (Reis & Alves 1997a, Reis et al. 1998). Several authors reported non-feeding larval stage for different phytoseiid species (Chant 1959, Putman 1962, McMurtry & Scriven 1964, Ma & Laing (1973), Moraes &, McMurtry 1981). This was not the case for the species used in the present study as well as in the study conducted by Gravena et al. (1994). However larvae of I. zuluagai and E. alatus were not seen feeding when they were given only castor bean pollen (Ricinus communis L.) as food (Reis & Alves 1997a, Reis et al. 1998).
Nymphs of the predators showed a performance similar to that of females, except for E. alatus when the prey was in the egg stage. Such nymphs showed a considerably lower prey in capacity than females. Male predators were more effective in preying on larvae.
The larval phase of the ringspot mite was the most consumed by predators, followed by the egg phase. The adult of B. phoenicis was less preferred for predation (Table 1). Similar results were obtained by Gravena et al. (1994) for E. citrifolius preying on B. phoenicis on citrus leaves.
The results showed how important is the preservation of the predatory mites I. zuluagai and E. alatus in the coffee crop, because of their high potential for preying on B. phoenicis.
To the Consórcio Brasileiro de Pesquisa e Desenvolvimento do Café - CBP&D/Café, Fundação de Amparo à Pesquisa do Estado de Minas Gerais - FAPEMIG and Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq for the financial support and scholarship granted.
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