Efeito da Densidade de Presa nas Respostas Funcional e Numérica de Duas Espécies deÁcaros Predadores (Acari: Phytoseiidae)RESUMO -Ácaros da família Phytoseiidae são os inimigos naturais de ácaros-praga mais importantes e estudados. Uma questão freqüentemente levantada é se os fitoseídeos podem reduzir altas densidades de ácaros fitófagos a baixos níveis. PALAVRAS-CHAVE: Iphiseiodes zuluagai, Euseius alatus, Brevipalpus phoenicis, citros, cafeeiroABSTRACT -Phytoseiidae mites are the most important and studied natural enemies of pest mites. A question frequently raised is whether phytoseiid may reduce high densities of phytophagous mites. Studies of functional and numerical responses may help to answer this question. The aim of this work was to evaluate the potential predation success of Iphiseiodes zuluagai Denmark and Muma and Euseius alatus DeLeon (Acari: Phytoseiidae) on Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae), vector of the citrus leprosis and the coffee ringspot viruses. Bioassays were performed in the laboratory. Adult females of each predator were isolated in arenas made with citrus leaves (3-cm diameter). Immature stages of B. phoenicis were offered as prey, at the following numbers/arena: 1, 2, 5, 10, 20, 30 and 35 (seven replicates), 45 (four replicates), 55 (three replicates) and 70, 100, 125, 200 and 300 (two replicates). The number of killed prey and of eggs laid by the predators was evaluated every 24h, during eight days. Killed prey was replaced daily by new prey. For both predatory mites, a positive and highly significant correlation was found between the numbers of prey offered and killed. The average daily oviposition rate also increased with the number of killed prey. At the lower densities, E. alatus killed and ate more B. phoenicis than I. zuluagai. The opposite was observed at the highest densities. It is possible that E. alatus can reduce B. phoenicis population even at low prey densities, and I. zuluagai can do the same also at high densities. The fact that E. alatus requires less prey than I. zuluagai suggests that its survivorship may be higher than that of I. zuluagai at low prey densities. KEY WORDS: Iphiseiodes zuluagai, Euseius alatus, Brevipalpus phoenicis, citrus, coffee plant 462Reis et al.

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Resumo -O objetivo deste trabalho foi identificar ácaros na cultura de pinhão-manso e em espécies de plantas espontâneas associadas. Para isso, foram avaliadas a riqueza e a abundância de ácaros em plantas de pinhão-manso e em 14 espécies de plantas espontâneas associadas. As amostragens foram realizadas por meio de coletas mensais de folhas de plantas de pinhão-manso e de plantas espontâneas, nas entrelinhas do cultivo. Foram encontradas quatro espécies de ácaros predadores -Amblyseius tamatavensis, Paraphytoseius multidentatus, Typhlodromalus aripo e Typhlodromalus clavicus -, com potencial para uso no controle biológico de ácaros-praga na cultura do pinhão-manso, e duas importantes espécies de ácaros fitófagos -Brevipalpus phoenicis e Tarsonemus confususdesconhecidas como praga da cultura. Entre as plantas espontâneas avaliadas, quatro espécies -Hyptis suaveolens, Peltaea riedelii, Urochloa mutica e Andropogon gayanus -abrigam grande riqueza e abundância de ácaros predadores, enquanto oito destacaram-se pela diversidade de ácaros fitófagos.Termos para indexação: Jatropha curcas, controle biológico, fitófagos, plantas invasoras. Acarofauna in physic nut culture and associated spontaneous weedsAbstract -The objective of this work was to identify mites in physic nut culture, and in associated spontaneous weed species. For this, mite richness and abundance on physic nut plants and on 14 species of associated spontaneous weeds were evaluated. Samplings were done with monthy collections of leaves from physic nut plants and from weeds, between planting lines. Four species of predatory mites -Amblyseius tamatavensis, Paraphytoseius multidentatus, Typhlodromalus aripo and Typhlodromalus clavicus -, with potential for biological control of pest mites on physic nut culture, and two species of phytophagous mites -Brevipalpus phoenicis and Tarsonemus confusus -, not yet known as pests of the culture were found. Among the evaluated spontaneous weeds, four species -Hyptis suaveolens, Peltaea riedelii, Urochloa mutica and Andropogon gayanus -harbor great richness and abundance of predatory mites, whereas eight harbored a high diversity of phytophagous mites.

Seasonal changes in climate and plant diversity are known to affect the population dynamics of both pests and natural enemies within agroecosystems. In Brazil, spontaneous plants are usually tolerated in small-scale physic nut plantations over the year, which in turn may mediate interactions between pests and natural enemies within this agroecosystem. Here, we aimed to access the influence of seasonal variation of abiotic (temperature, relative humidity and rainfall) and biotic (diversity of spontaneous plants, overall richness and density of mites) factors on the communities of phytophagous and predatory mites found in a physic nut plantation and its associated spontaneous plants. Mite sampling was monthly conducted in dicotyledonous and monocotyledonous leaves of spontaneous plants as well as in physic nut shrubs over an entire year. In the dry season there was a higher abundance of phytophagous mites (Tenuipalpidae, Tarsonemidae and Tetranychidae) on spontaneous plants than on physic nut shrubs, while predatory mites (Phytoseiidae) showed the opposite pattern. The overall density of mites on spontaneous plants increased with relative humidity and diversity of spontaneous plants. Rainfall was the variable that most influenced the density of mites inhabiting physic nut shrubs. Agroecosystems comprising spontaneous plants associated with crops harbour a rich mite community including species of different trophic levels which potentially benefit natural pest control due to increased diversity and abundance of natural enemies.

-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.