The effects of tangerine (Citrus reticulata Blanco), lemon (Citrus medica limonum Lush), pear orange (Citrus sinensis L. Osbeck), red copaiba (Copaifera langsdorffii Desf.), rosemary (Baccharis dracunculifolia De Candole), eucalyptus (Eucalyptus globulus Labillardière and E. citriodora Hook), lemongrass (Cymbopogon citratus Stapf.) and citronella (Cimbopogon nardus Linnaeus) oils at several concentrations on Zabrotes subfasciatus (Boheman) were studied. In toxicity tests, grains of Phaseolus vulgaris L. cv. Rajadinho were impregnated with oils and infested with adults of Z. subfasciatus up to 24 hours old. All tested oils were effective in reducing the viable egg-laying and adult emergence of this pest, in function of the concentrations used, highlighting E. citriodora and E. globulus oils which caused 100% effectiveness from 0.5 mL Kg -1 concentration. In repellency tests, two arenas consisting of plastic containers, connected symmetrically to a central box by two plastic tubes were used. In one of the boxes, untreated beans were placed and on the other ones beans treated with each oil concentration were used. In the central box, five couples of Z. subfasciatus were released. Grains of P. vulgaris treated with oils of E. citriodora, C. citratus and C. oleifera reduced the attraction percentage of Z. subfasciatus adults, while the E. globulus increased this percentage. The percentages of reduced viable eggs ranged from 17.9% (C. medica limonum) to 93.3% (C. nardus), while the reduction on the number of emerged insects was 23.9% and 95.9%, respectively for these same oils. KEYWORDS: Botanical insecticides, bean weevil, bioactivity, behavioral effect.Toxicidade e repelência de óleos essenciais a Zabrotes subfasciatus (Boheman) (Coleoptera, Chrysomelidae, Bruchinae) em grãos de Phaseolus vulgaris L. RESUMOEstudaram-se os efeitos dos óleos de tangerina 'Cravo' (Citrus reticulata Blanco), limão-siciliano (Citrus medica limonum Lush), laranja 'Pêra' (Citrus sinensis L. Osbeek), copaíba-vermelha (Copaifera langsdorffii Desf.), alecrim-do-campo (Baccharis dracunculifolia De Candole), eucalipto (Eucalyptus globulus Labillardière e Eucalyptus citriodora Hook), capim-santo (Cymbopogon citratus Stapf.) e citronela (Cymbopogon nardus L.), em diversas concentrações, sobre Zabrotes subfasciatus (Boheman). Nos testes de toxicidade, grãos de Phaseolus vulgaris L. cv. Rajadinho foram impregnados com os óleos e infestados com adultos de Z. subfasciatus com até 24 horas de idade. Todos os óleos foram eficientes na redução da postura de ovos viáveis e na emergência de adultos desta praga, em função das concentrações utilizadas, destacando-se E. citriodora e E. globulus, que a partir da concentração de 0,5 mL Kg -1 já causaram 100% de eficácia. Nos testes de repelência utilizaram-se arenas compostas por dois recipientes plásticos, interligados simetricamente a uma caixa central por dois tubos plásticos. Numa das caixas colocaram-se grãos de feijão não tratados e, na outra, feijões tratados com cada uma das concentrações de ól...
The Chilocorini lady beetles Tenuisvalvae notata (Mulsant) and Cryptolaemus montrouzieri Mulsant are important biological control agents being able to share their habitat and compete for their preferred prey, mealybugs. Whereas T. notata is native to South America, C. montrouzieri is an Australian species introduced in Brazil in a biological control program of mealybugs. This work investigated the cannibalism and intraguild predation between these species in the absence of prey. To test for intraguild predation, one individual larva (instars 1-4) from each species was confined for 24 h with another larva of the same instar or the next instar, in a total of 10 combinations. In addition, we measured predation of T. notata adults upon eggs, larvae, pre-pupae and pupa of C. montrouzieri, and vice versa. Cannibalism within the species was also tested across adults, larvae and eggs. Results showed asymmetric interactions in favour of C. montrouzieri, which acted as intraguild predator more than 80% of the time when paired with larvae of T. notata either of the same or different instar. In addition, C. montrouzieri adults preyed more upon larvae and eggs of T. notata than the contrary. There was no intraguild predation upon pre-pupae and pupae. Cannibalism was high upon eggs and first instar larvae of T. notata (89.5% and 65%) and C. montrouzieri (100% and 55%), respectively. Therefore, the exotic C. montrouzieri outcompeted the native T. notata and could become a threat to this endemic species in areas of simultaneous occurrence and under prey scarcity. Thus, the interactions between these lady beetles could affect the success of biological control of mealybugs.
BACKGROUND: White and colored fiber cotton cultivars have been developed to increase production and opportunities for family farming. The broad mite, Polyphagotarsonemus latus (Banks) is an important pest in cotton crops, nevertheless, different cotton cultivars may influence its host selection and population growth. For P. latus control, acaricides application is commonly performed, although less is known about the sublethal effects of these products. Thus, the host preference and instantaneous rate of increase (r i) of P. latus were evaluated on white and colored cotton cultivars, as well as the lethal and sublethal effects of acaricides through mortality tests and population growth. RESULTS: In free-choice tests to evaluate host preference among white and colored cotton cultivars, no preference was observed for P. latus. The instantaneous r i values were positive for all tested cultivars, however, differences were observed between the colored BRS Rubi and the white BRS 201. The population growth of P. latus decreased with increasing concentrations of the acaricides abamectin, spirodiclofen, azadirachtin and spiromesifen. Nevertheless, azadirachtin and spiromesifen presented positive r i values even at the highest lethal concentrations (LC 90), while abamectin and spirodiclofen provided negative r i values of P. latus from LC 90 and LC 70 , respectively. CONCLUSION: No host preference of P. latus was observed among white and colored cotton cultivar. Abamectin and spirodiclofen presented relevant sublethal effects that should be considered for the integrated management of this pest.
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