Mayara Cristina Lopes

Bioassay method for toxicity studies of insecticide formulations to Tuta absoluta (meyrick, 1917)

O principal metodo utilizado no controle da traca-do-tomateiro Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) e a aplicacao de inseticidas. As tecnicas atuais de avaliacao da toxicidade de inseticidas sobre essa praga nao simulam a situacao de campo e nao possibilitam a verificacao se as doses usadas no campo sao eficientes no seu controle. Assim, neste trabalho, objetivou-se desenvolver uma metodologia que represente as condicoes de campo para inseticidas de acao rapida (neurotoxicos e inibidores respiratorios) e de acao lenta (Bacillus thuringiensis e reguladores de crescimento. A metodologia mais eficiente para estudos de toxicidade de formulacoes comerciais a T. absoluta foi a imersao de folhas em calda inseticida. Para os bioensaios de inseticidas de acao rapida, sugere-se que estes sejam realizados em placas de Petri, contendo foliolos de tomate da 4a folha a partir do apice da planta, infestados com 10 larvas de 3o instar e eles podem durar 48 horas. Quanto aos bioensaios de toxicidade de inseticidas de acao lenta, sugere-se que sejam realizados em garrafas PET transparentes, de dois litros, contendo a 4a folha de tomate a partir do apice da planta infestada com 10 larvas de 2o instar e seu peciolo inserido em vidro de 120 mL contendo agua. Nesse caso, o bioensaio pode durar sete dias sem prejuizo na eficiencia.

Intermediate-energy differential and integral cross sections for vibrational excitation in α-tetrahydrofurfuryl alcohol

Differential and integral cross section measurements, for incident electron energies in the 20-50 eV range, are reported for excitation of several composite vibrational modes in α-tetrahydrofurfuryl alcohol (THFA). Optimisation and frequency calculations, using GAUSSIAN 09 at the B3LYP/aug-cc-pVDZ level, were also undertaken for the two most abundant conformers of THFA, with results being reported for their respective mode classifications and excitation energies. Those calculations assisted us in the experimental assignments of the composite features observed in our measured energy loss spectra. There are, to the best of our knowledge, no other experimental or theoretical data currently available in the literature against which we can compare the present results.

Toxicity of botanical insecticides on Diaphania hyalinata, their selectivity for the predatory ant Paratrechina sp., and their potential phytotoxicity on pumpkin

ABSTRACT The use of botanical insecticides could be an alternative efficient pest management in Cucurbitaceae against melonworm Diaphania hyalinata and less harmful to its predator. Few studies jointly assess the efficiency of botanical insecticides, their effects on pest, and their effect on the natural enemy and target crop. Here we examine (1) their impact against the melonworm D. hyalinata, a key pest of Cucurbitaceae, (2) their toxicity to the predatory ant Paratrechina sp., and (3) their phytotoxicity to pumpkin plants. The botanical insecticides citronella oil and eucalyptus oil were highly toxic to D. hyalinata and they exhibited to be less harmful for the predatory ant Paratrechina sp. Andiroba oil, eucalyptus oil, garlic extract, and citronella oil caused feeding inhibition of the D. hyalinata larvae. Eucalyptus oil, andiroba oil, garlic extract, and rotenone inhibited the oviposition of D. hyalinata. None of the insecticides was phytotoxic to pumpkin plants. Eucalyptus oil and citronella oil have induced high mortality and altered the behavior of target pests. In addition, they were selective for the predator Paratrechina sp. and not exhibited phytotoxicity on pumpkin plants. Eucalyptus oil and citronella oil seem the most promising compounds for incorporation into melonworm management programs, because they induced high mortality and altered the behavior of target pests and were selective for the predator Paratrechina sp.

Recent progress in electron scattering from atoms and molecules

We present and discuss recent results, both experimental and theoretical (where possible), for electron impact excitation of the 3s[32]1 and 3s′[12]1 electronic states in neon, elastic electron scattering from the structurally similar molecules benzene, pyrazine, and 1,4-dioxane and excitation of the electronic states of the important bio-molecule analogue α-tetrahydrofurfuryl alcohol. While comparison between theoretical and experimental results suggests that benchmarked cross sections for electron scattering from atoms is feasible in the near-term, significant further theoretical development for electron-molecule collisions, particularly in respect to discrete excitation processes, is still required.We present and discuss recent results, both experimental and theoretical (where possible), for electron impact excitation of the 3s[32]1 and 3s′[12]1 electronic states in neon, elastic electron scattering from the structurally similar molecules benzene, pyrazine, and 1,4-dioxane and excitation of the electronic states of the important bio-molecule analogue α-tetrahydrofurfuryl alcohol. While comparison between theoretical and experimental results suggests that benchmarked cross sections for electron scattering from atoms is feasible in the near-term, significant further theoretical development for electron-molecule collisions, particularly in respect to discrete excitation processes, is still required.

Sequential sampling plans and economic injury levels for Empoasca kraemeri on common bean crops at different technological levels

BACKGROUND Empoasca kraemeri is an important pest on common bean crops at different technological levels. However, for this pest on this crop, economic injury levels have not yet been determined and plan for sequential sampling plans has not yet been developed. Thus, the objectives of this research were to develop E. kraemeri sequential sampling plans and to determine economic injury levels in the common bean at different crop technological levels. RESULTS Common bean plants tolerate low attack intensities of this pest (up to 1 adult plant-1 ). However, with an increase in attacks, there is a reduction in grain production by the plants. The economic injury levels were 0.48, 0.39 and 0.35 adults sample-1 (leaf beating on a tray) for crops with low (1200 kg ha-1 ), medium (1800 kg ha-1 ) and high (2400 kg ha-1 ) technological levels, respectively. Sequential sampling plans and the standardized plan produced similar decisions. However, in these decisions there was a time saving of more than 60% compared with the standardized plan. CONCLUSION All three economic injury levels determined and the sequential sampling plans developed in this study are suitable for incorporation into integrated management programs for common bean pests because they can be used by farmers operating at various technological levels to make adequate and rapid decisions.

Toxicity of new pyrethroid in pest insects Asciamonuste and Diaphania hyalinata, predator Solenopsis saevissima and stingless bee Tetragonisca angustula

ABSTRACT There is increasing demand for new products for vegetable pest management. Thus, the aim of this study was to assess the toxicity of pyrethroids with acid moiety modifications to measure the insecticidal activity of these compounds on the lepidopteran vegetable pests Diaphania hyalinata (L.) (Lepidoptera: Pyralidae) and Asciamonuste (Latreille) (Lepidoptera: Pieridae) and evaluate their selectivity for the predatory ant Solenopsis saevissima (F. Smith) (Hymenoptera: Formicidae) and pollinator Tetragonisca angustula (Latreille) (Hymenoptera: Apidae: Meliponinae). Racemic mixtures of five new pyrethroids (30 µg molecule mg−1 insect body weight) resulted in high (100%) and rapid (stable LD50 after 12 h) mortality in D. hyalinata and A. monuste. In A. monuste, the trans-pyrethroid [12] isomer showed similar toxicity to permethrin. For D. hyalinata, the trans-pyrethroid [9] isomer and cis-pyrethroid [10] isomer were as toxic as permethrin. Due to their low selectivity, these new pyrethroids should be applied on the basis of ecological selectivity principles to minimize impacts on nontarget organisms S. saevissima and T. angustula.

Active insecticides for Diaphania hyalinata selective for the natural enemy Solenopsis saevissima

ABSTRACT The objective of this study was to determine the toxicity of the nine synthetic dienamides against the insect pest Diaphania hyalinata (melonworm) and the selectivity of these substances for the predator Solenopsis saevissima (fire ant). Four bioassays were conducted. To begin with, the dienamides that caused high mortality of D. hyalinata have been selected. In the second bioassay the dose-mortality curves of the selected dienamides have been constructed. In the third bioassay, the survival curves for D. hyalinata and the elapsed time to kill 50% of their population have been determined. In the fourth biological test, the selectivity of the substances to the predator S. saevissima has been evaluated. The most active (2E,4E)-N-butylhexa-2,4-dienamide 3d has killed 95% of the melonworm, D. hyalinata, and less than 10% of the natural enemy S. saevissima. The results presented by this compound are superior to the outcome displayed by the commercial insecticide Malathion®. Three of the dienamides prepared in this manuscript have proven to be selective in killing the pest, but not the beneficial insect.

INSECTICIDAL ACTIVITY OF DIENAMIDES ON CABBAGE CATERPILLAR AND BENEFICIAL INSECTS

Mayara Cristina Lopes,a Elson Santiago Alvarenga,c,* Alex Ramos Aguiar,c Izailda Barbosa dos Santos,b Gerson Adriano Silva,d Lucas de Paula Arcanjob and Marcelo Coutinho Picançob Departamento de Fitotecnia, Universidade Federal de Viçosa, Viçosa – MG, Brasil Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa – MG, Brasil Departamento de Química, Universidade Federal de Viçosa, Viçosa – MG, Brasil Centro de Ciências e Tecnologias Agropecuárias, Universidade Estadual Norte Fluminense, Campos dos Goytacazes – RJ, Brasil

Sequential sampling plans and economic injury level for Empoasca kraemeri on different technological levels of common bean crops

BACKGROUND Empoasca kraemeri is an important pest on common bean crops at different technological levels. However, for this pest on this crop, economic injury levels have not yet been determined and plan for sequential sampling plans has not yet been developed. Thus, the objectives of this research were to develop E. kraemeri sequential sampling plans and to determine economic injury levels in the common bean at different crop technological levels. RESULTS Common bean plants tolerate low attack intensities of this pest (up to 1 adult plant-1 ). However, with an increase in attacks, there is a reduction in grain production by the plants. The economic injury levels were 0.48, 0.39 and 0.35 adults sample-1 (leaf beating on a tray) for crops with low (1200 kg ha-1 ), medium (1800 kg ha-1 ) and high (2400 kg ha-1 ) technological levels, respectively. Sequential sampling plans and the standardized plan produced similar decisions. However, in these decisions there was a time saving of more than 60% compared with the standardized plan. CONCLUSION All three economic injury levels determined and the sequential sampling plans developed in this study are suitable for incorporation into integrated management programs for common bean pests because they can be used by farmers operating at various technological levels to make adequate and rapid decisions.