Toxicity of neem oil to the cassava green mite Mononychellus tanajoa (Bondar) (Acari: Tetranychidae)

O artigo não contém o resumo português.Neem (Azadirachta indica A. Juss.)-derived pesticides have been used against a wide range of agricultural pests including tetranychid mites. Approaches combining lethal and sublethal toxicity studies of neem pesticides towards tetranychid mites are necessary to a comprehensive evaluation of such products. Here, we evaluated the lethal and sublethal toxicity of the neem oil Bioneem to the cassava green mite Mononychellus tanajoa (Bondar) by integrating lethal concentration (LC) with population growth and biological parameter studies. According to Probit analyses the concentration of neem oil Bioneem which kills 50% of the population (LC50) of M. tanajoa was 3.28 μL cm^-2, which is roughly twice the field concentration recommended of this biopesticide to control pest mites (1.7 μL cm^-2). The growth rate of the cassava green mite steadily decreased with dosages of neem oil. Furthermore, sublethal concentrations of the neem oil corresponding to the LC50 reduced the periods of the immature stages of M. tanajoa resulting in a shorter developmental time. Similarly, the number of eggs per day and the number of eggs per female per day, a proxy for fecundity, were drastically reduced in M. tanajoa females exposed to the LC50 of neem oil. Based on our comprehensive approach we conclude that the neem oil showed lethal as well as sublethal toxicity on growth rate and biological parameters such as duration of immature stages and fecundity of the cassava green mite M. tanajoa and it could be used as an ecological alternative for the management of this pest

Suitability of the predatory mites Iphiseiodes zuluagai and Euseius concordis in controlling Polyphagotarsonemus latus and Tetranychus bastosi on Jatropha curcas plants in Brazil

One of the most promising plant species for biofuel production in Brazil is the physic nut Jatropha curcas. Major phytosanitary problems include the attack of two pest mite species, the broad mite Polyphagotarsonemus latus and the spider mite Tetranychus bastosi. Owing to pesticide-related problems, there is an increasing demand for sustainable environmental-friendly control methods such as biological control. In this study we evaluated the suitability of the predatory mite species Iphiseiodes zuluagai and Euseius concordis in controlling P. latus and T. bastosi on J. curcas. The number of T. bastosi killed by I. zuluagai was lower than the number of P. latus consumed.Euseius concordis preyed upon both T. bastosi and P. latus but the number of prey killed was always lower in comparison with I. zuluagai. However, P. latus and T. bastosi are suitable for the development of I. zuluagai and E. concordis as oviposition of both predators did not differ in relation to prey species. The preference of I. zuluagai for leaves of plants infested by either P. latus or T. bastosi, combined with the higher values for predation obtained by this predatory mite when fed on P. latus, compared to those values obtained by E. concordis, suggests that I. zuluagai can be more efficient than E. concordis in reducing populations of P. latus and T. bastosi under field conditions. Furthermore, we report here on the first record of predatory mites associated with P. latus and T. bastosi on native J. curcas plants in Brazil. In conclusion, we emphasize the crucial importance of predatory mites as agents of natural biological control of mite pests on J. curcas in small farms

Population structure and dynamics of the cassava green mite Mononychellus tanajoa (Bondar) and the predator Euseius ho (DeLeon) (Acari: Tetranychidae, Phytoseiidae)

Population structure and dynamics of the cassava green mite Mononychellus tanajoa and the predator Euseius ho (Acari: Tetranychidae, Phytoseiidae). Cassava is attacked by several pests, among which the cassava green mite Mononychellus tanajoa. Predatory mites of the family Phytoseiidae are major natural enemies of pestmites and are naturally found inhabiting cassava plants in the field. We evaluated the temporal variation of the developmental stages of M. tanajoa and the most abundant predatory mite in cassava fields in the study region, the phytoseiid Euseius ho. Densities of all developmental stages of M. tanajoa were low during the rainy season, increasing over the cultivation cycle of cassava and peaking in the dry season. Overall, the larval stage of M. tanajoa presented the lowest densities throughout time. Densities of all developmental stages of E. ho were low and remained constant throughout the cultivation cycle of cassava. The number of eggs, nymphs and adults of M. tanajoa was higher in comparison to the larval stage whereas there were no differences in densities of the stages of E. ho. Densities of all developmental stages of M. tanajoa were negatively correlated with precipitation. Densities of the stages of egg, nymph and adult of M. tanajoa were positively related while the stage of larva was negatively related to temperature. We conclude that it is important to consider the population structure in studies of population dynamics of arthropods as each developmental stage experiences and responds uniquely to the local environment over time

Parasitizing behavior of Cervellus piranga Penteado-Dias (Hymenoptera, Braconidae, Braconinae) on papaya borer weevil Pseudopiazurus obesus Marshall (Coleoptera, Curculionidae)

Parasitizing behavior of Cervellus piranga Penteado-Dias (Hymenoptera, Braconidae, Braconinae) on papaya borer weevil Pseudopiazurus obesus Marshall (Coleoptera, Curculionidae). The papaya borer weevil Pseudopiazurus obesus is a pest associated with papaya crops in Brazil and Cervellus piranga is a naturally-occurring parasitoid which may contribute to regulate populations of this pest. We aimed at describing the parasitizing behavior of the parasitoid C. piranga on papaya borer weevil P. obesus larvae under field conditions. The sequence of events related to the parasitizing behavior of C. piranga is similar to other braconid species and includes the location and recognition of the attacked host plant followed by walks on the host plant and touching it with the tip of the antennae and the ovipositor. In the following event, the parasitoid assesses the suitability of the host by speeding up antennae and ovipositor movements. After locating and accepting the host, the parasitoid remains inactive on oviposition aperture sites and starts moving the antennae. Afterwards, the parasitoid inserts its ovipositor and starts cleaning it repeatedly. The female of C. piranga inserts the ovipositor through the hole and lay one egg into the papaya weevil borer. After oviposition, the female cleans continuously both ovipositor and antennae before leaving to forage for a new host.<br>Comportamento de parasitismo de Cervellus piranga Penteado-Dias (Hymenoptera, Braconidae, Braconinae) sobre a broca-do-mamoeiro Pseudopiazurus obesus Marshall (Coleoptera, Curculionidae). A broca-do-mamoeiro Pseudopiazurus obesus é uma praga de cultivos de mamão no Brasil e Cervellus piranga é um parasitóide que ocorre naturalmente no campo e pode contribuir para a regulação da população desta praga. O objetivo do presente trabalho foi a descrição do comportamento de parasitismo do parasitoide C. piranga sobre larvas da broca-do-mamoeiro P. obesus em condições de campo. A sequência de eventos relacionados ao parasitismo de C. piranga é similar a outras espécies de braconídeos e inclui a localização e o reconhecimento da planta hospedeira atacada, caminhamento na planta e toque desta com as antenas e o ovipositor. No próximo evento, o parasitoide acessa a adequabilidade do hospedeiro através do aumento dos movimentos da antena e do ovipositor. Após localizar e aceitar o hospedeiro, o parasitoide fica imóvel no sítio de oviposição e inicia a movimentar a antena. Em seguida, o parasitoide insere o ovipositor e o limpa repetidamente. A fêmea de C. piranga insere o ovipositor através da abertura e deposita um ovo na broca-do-mamoeiro. Após a oviposição, a fêmea limpa continuamente o ovipositor e a antena e abandona a planta para um novo forrageamento

Lethal and sub-lethal selectivity of fenbutatin oxide and sulfur to the predator Iphiseiodes zuluagai (Acari: Phytoseiidae) and its prey, Oligonychus ilicis (Acari: Tetranychidae), in Brazilian coffee plantations

Lethal concentration (LC) has been widely used to estimate pesticide toxicity. However, it does not consider the sub-lethal effects. Therefore we included the instantaneous rate of increase in association with LC to estimate population-level effects of the acaricides fenbutatin oxide and sulfur on the predator Iphiseiodes zuluagai and its prey, the phytophagous southern red mite, Oligonychus ilicis. The predator was 32.84x and 17.20x more tolerant to fenbutatin oxide and sulfur, respectively, than its prey, based on LC50 estimates obtained from acute concentration–mortality bioassays. The instantaneous rate of population growth in both mite species decreased with increasing acaricide concentration. Both acaricides provided effective control of O. ilicis at their recommended concentrations, but sulfur drastically compromised the predator populations quickly leading them to extinction due to the low reproductive potential of this species compared with its prey

Ultrastructural analysis of salivary glands in a phytophagous stink bug revealed the presence of unexpected muscles.

The exceptional abilities of stink bugs (Hemiptera: Pentatomidae) to colonize a diverse group of plants have been attributed to the feeding behaviors and the functions of the salivary complex of these insects. Here, we describe the ultrastructure of the salivary glands of the Neotropical brown stink bug, Euschistus heros, which is a major component of the pentatomid pest complex on soybeans, Glycine max, in the neotropics. Our results revealed a salivary gland complex consisting of two lobes (i.e., anterior and posterior), with a constriction between them (i.e., the hilum), in which the salivary and accessory gland ducts are inserted. The principal gland epithelium has a single layer of cells lining an enlarged lumen filled with saliva, and these cells are cuboidal, rich in rough endoplasmic reticulum and secretory vesicles, with well-developed nuclei, all of which are typical features of protein-secreting cells. We report, for the first time in insects, the presence of a layer of muscle cells surrounding the columnar hilum epithelium. The accessory salivary gland cells are cuboidal with nuclei containing condensed chromatin and cytoplasm rich in vacuoles and rough endoplasmic reticulum, indicating the potential involvement of these glands in water transport/secretion. The lumen content of each lobe of the principal gland suggests that the lobes produce different compounds. Thus, our results suggest that the E. heros salivary complex might have unconventional mechanisms to mix/release saliva, which might help explain the polyphagous abilities of these insects

Population dynamics of Aceodromus convolvuli (Acari: Mesostigmata: Blattisociidae) on spontaneous plants associated with Jatropha curcas in central Brazil

Spontaneously growing plants are commonly considered competitors of cultivated plants. Owing to the lack of specificity of many arthropods, spontaneous plants may be attacked by the same arthropods that attack cultivated plants and they may also harbor natural enemies of organisms harmful to cultivated plants. Aceodromus convolvuli Muma (Blattisociidae) has been reported recently in relatively large numbers in Tocantins state, central Brazil, mostly on Helicteres guazumifolia Kunth (Malvaceae). Very little has been reported about the population dynamics of blattisociid mites under field conditions. The objective of this work was to study the population dynamics of A. convolvuli in Gurupi, Tocantins state, to evaluate its possible interaction with associated mites. Monthly samples were taken from leaves of the 11 most abundant and frequent spontaneous plants in a Jatropha curcas L. (Euphorbiaceae) plantation. About 96.5 % of the specimens of A. convolvuli were collected in the rainy season. The patterns of variation of the population of A. convolvuli and of predators belonging to the family Phytoseiidae were similar, but A. convolvuli was much more numerous than all phytoseiid specimens combined. Highly significant correlations were observed between A. convolvuli densities and relative humidity or diversity of spontaneous plants. When only mites on H. guazumifolia were considered, highly significant correlation was also observed between densities of A. convolvuli and of mites of the family Tetranychidae. The results suggested that A. convolvuli could be a predator of tenuipalpid and/or tetranychid mites. Studies about its biology are needed to determine its preferred food sources and potential as biological control agent.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES