Acaricide-impaired functional and numerical responses of the predatory mite, Amblyseius largoensis (Acari: Phytoseiidae) to the pest mite Raoiella indica (Acari: Tenuipalpidae)

The suppression of pest populations by a predator depends on two basic components of the predator-prey interaction: the functional and the numerical responses of the predator. Such responses can be affected by exposure to acaricides. In the present study, the effects of acaricides (abamectin, azadirachtin, fenpyroximate, and chlorfenapyr) on the functional and numerical responses of the predatory mite, Amblyseius largoensis (Acari: Phytoseiidae) an important natural enemy of the pest mite, Raoiella indica (Acari: Tenuipalpidae), were investigated. The exposure of A. largoensis to acaricides occurred through contact with a surface contaminated with dried acaricide residue. Subsequently, A. largoensis exhibited a type II functional response, which was not altered by exposure of any acaricides. However, exposure to abamectin resulted in a decrease in the average mean numbers of prey consumed by a predator. Exposure to acaricides increased prey handling time by 67%, 25%, 38%, and 35% for abamectin, azadirachtin, fenpyroximate, and chlorfenapyr, respectively. Exposure to abamectin reduced the attack rate of A. largoensis by 52%. The numerical response of A. largoensis was only affected by exposure to abamectin, where just 60% of the females oviposited, and regardless of the prey density, the average mean numbers of eggs/female/day was always less than 0.4. The food conversion efficiency into biomass of A. largoensis eggs decreased with increasing prey density, and this trend was not altered by exposure to any acaricides. However, exposure to abamectin drastically compromised the oviposition of A. largoensis, showing no increase in egg production with increasing prey density.

Survey of phytoseiid mites (Acari: Mesostigmata, Phytoseiidae) in citrus orchards and a key for Amblyseiinae in Vietnam

Citrus is the second largest fruit crop in Vietnam. Phytoseiid mites are important natural enemies of mite pests and small insects in citrus orchards. By examining the specimens collected from three citrus orchards in the Mekong Delta in the south of Vietnam, a new record of phytoseiid mite Amblyseius obtuserellus Wainstein and Begljarov, 1971 was found and two other species Amblyseius largoensis (Muma, 1955) and Euseius ovalis (Evans, 1953) were also obtained. Herein, they are re-described and illustrated based on the current specimens. A key for Amblyseiinae in Vietnam is also provided

Biological performance of the predatory mites Amblyseius largoensis and Euseius concordis fed on eggs of Aleurodicus cocois

No abstract, but the first three sentences are shown below:Giant whiteflies, Aleurodicus cocois, commonly occur in some fruit trees, especially on cashew trees, and are actually recognized as a key pest in this crop. It is possible that some of the phytoseiid species that commonly occur on cashew trees have the potential to be used to control the giant whitefly. Amblyseius largoensis and Euseius concordis has been suggested as potential natural enemies of the giant whitefly. Thus, the present study evaluated the development and reproduction of A. largoensis and E. concordis when fed exclusively on giant whitefly eggs.

Functional response of Amblyseius largoensis to Raoiella indica eggs is mediated by previous feeding experience

The mechanisms involved in the acceptance and choice of prey by predatory mites are still poorly understood. The present study was designed to determine whether previous feeding experience of Amblyseius largoensis (Muma) (Acari: Phytoseiidae) on Raoiella indica Hirst (Acari: Tenuipalpidae) eggs could influence the predator’s functional response and related parameters. The consumption of R. indica eggs by experienced and naïve female A. largoensis was evaluated under increasing densities of eggs. Regardless of the predators’ previous experience, a gradual increase in the number of eggs consumed and a tendency to stabilize at higher densities were observed. Proportionally, egg consumption decreased with increasing egg densities, indicating a type II functional response for both experienced and naïve predators. Experienced and naïve predators also had the same attack rate. However, naïve predators had a handling time almost 50% longer than experienced predators and showed lower variation in egg consumption and lower peak egg consumption. The results of the present study demonstrate that previous feeding experience may alter parameters of the functional response of A. largoensis to R. indica eggs but not the type of response. Possibly, longer associations between native populations of A. largoensis and R. indica results in more aggressive predator populations.

Functional response of the predaceous mites Amblyseius largoensis and Euseius concordis when feeding on eggs of the cashew tree giant whitefly Aleurodicus cocois

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.

Description of five new species and re-description of two species of Amblyseius (Acari: Phytoseiidae) from West Bengal, India

In this paper five new mite species are described from West Bengal, India—Amblyseius dahliae sp. nov., A. bengalensis sp. nov., A. brachycalyx sp. nov., A. conulus sp. nov., A. parbatabasii sp. nov., and two species are re-described—Amblyseius largoensis (Muma, 1955) and A. herbicolus (Chant, 1959) (Acari: Phytoseiidae).

Acarofauna em açaizeiro (Euterpe oleracea Mart.) conduzido em diferentes sistemas de cultivo

O açaizeiro (Euterpe oleraceae) é a mais importante palmeira do gênero Euterpe conhecida no Brasil, que é cultivada em sistemas de cultivo solteiro e consorciado. Apesar da grande utilidade, esta palmeira se destaca no fornecimento de dois produtos alimentares economicamente rentáveis, os frutos e o palmito. Em razão da sua importância, objetivou-se com este trabalho realizar o levantamento da acarofauna presente em cultivos de açaizeiro no município de São Luís - Maranhão. As amostragens foram realizadas mensalmente, no período de agosto de 2012 a julho de 2013, em açaizeiros cultivados em dois sistemas plantio: solteiro e consorciado. A análise faunística foi feita pelo programa ANAFAU, no qual foram determinados os índices de abundância, frequência, dominância, constância e diversidade. Foram encontrados 6.274 ácaros, sendo 4.748 no sistema de consórcio e 1.526 no cultivo solteiro. Entre a ocorrência de ácaros fitófagos, as famílias Tenuipalpidae e Tetranychidae se destacaram nos dois cultivos. Em relação às famílias de ácaros predadores, a Phytoseiidae foi considerada superdominante, superabundante, superfrequente e constante; as espécies Amblyseius largoensis, Euseius concordis e Iphiseiodes zuluagai foram dominantes em ambos os sistemas de cultivo, porém o cultivo consorciado apresentou maior diversidade em relação ao cultivo solteiro. Na flutuação populacional, observaram-se maiores populações de ácaros nos períodos de menor precipitação pluviométrica nos dois sistemas estudados.