Toxicidade e efeitos subletais de produtos químico, biológico e botânico para Putella xylostella (l.) (Lepidoptera: Plutellidae) e otimização na técnica de criação em condições de laboratório
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Data
2022-01-04
Autores
Vieira, Natalia Fernanda [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), a traça das crucíferas, é um dos principais insetos-praga de crucíferas no mundo todo, cujos danos podem comprometer gravemente a produção dessas hortaliças. O método mais empregado para o controle dessa traça ainda é a utilização de produtos químicos, onde os inseticidas sintéticos são os mais aplicados, devido a fácil disponibilidade no mercado e rápido efeito sobre as lagartas. Porém, frequentes aplicações de inseticidas para controle da praga, combinado com fatores biológicos de P. xylostella, podem contribuir com a seleção de indivíduos resistentes. Uma das alternativas ao controle químico é a utilização de bioinseticidas no controle de lepidópteros-praga, como aqueles à base da bactéria entomopatogênica Bacillus thuringiensis Berliner. Outra opção para programas de Manejo Integrado de Pragas como ferramenta promissora no controle de pragas é a utilização de substâncias de origem vegetal com propriedades inseticidas, principalmente na agricultura familiar e em sistemas orgânicos de cultivo. São produtos considerados de baixo impacto ambiental, uma vez que são rapidamente degradados sob a ação de luz, umidade, chuva e outros fatores abióticos. É de extrema importância estudos relacionados à métodos alternativos para o combate a esta praga que se ajustem ao seu manejo integrado. Trabalhos que avaliem a eficiência dos inseticidas em ovos, uma das fases de grande vulnerabilidade da praga, são importantes também para orientar a rotação de produtos em programas de manejo. Visando fornecer informações ao manejo desse lepidóptero-praga, foi utilizado o inseticida químico ciantraniliprole (Benevia®), o biológico Bacillus thuringiensis subsp. kurstaki (Dipel®) e o extrato hexânico de Piper cubeba Linnaeus, 1753 (Piperales: Piperaceae). Neste sentido, o objetivo deste trabalho foi investigar qual o melhor substrato para manutenção da criação dessa espécie em laboratório, a ação dos inseticidas em ovos e na oviposição de P. xylostella, bem como o efeito agudo das concentrações letais e os efeitos subletais de inseticidas químico, biológico e extrato da planta P. cubeba, além das toxicidades residuais, assim como avaliar a fitotoxicidade do extrato em mudas de couve em casa de vegetação e folhas de couve destacadas das plantas em laboratório. Com esse estudo foi possível verificar que a concentração adequada do extrato de P. cubeba que mata a praga em couve sem que haja fitotoxicidade em folhas e mudas é de 1%. Ao avaliar os parâmetros biológicos sob influência das concentrações subletais (CL25 e CL10), verificou-se que os inseticidas causaram alterações no período larval e pupal, no peso de pupas e na fecundidade, além de influenciar o crescimento populacional. Para a ação dos inseticidas em ovos e na oviposição, o presente estudo mostrou que o extrato de P. cubeba apresenta maior ação tóxica em ovos e influencia negativamente na oviposição de P. xylostella. Em relação aos substratos, disco de folha de couve e disco de folha de couve sobre papel filtro umedecido com água deionizada mostraram ser os melhores substratos para oviposição de P. xylostella, sem perda na qualidade dos insetos. Diante dessas questões, espera-se que os resultados obtidos nesta tese forneçam subsídios para auxiliar a obtenção de insetos de qualidade para pesquisas, além de implementar alternativas visando ao controle da traça-das-crucíferas.
Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), diamondback moth, is one of the main insect pest of crucifers worldwide, whose damage can seriously compromise the production of these vegetables. The most used method for its control is still the use of chemical products, in which synthetic insecticides are the most applied, due to their easy availability in the market and quick effect on larvae. However, the continuous insecticide applications for pest control, combined with P. xylostella biological factors, can contribute to the selection of resistant individuals. One of the alternatives to avoid or minimize chemical control is the use of bioinsecticides to control lepidopteran pests, such as those based on the entomopathogenic bacteria Bacillus thuringiensis Berliner. Another suitable option for Integrated Pest Management programs as a promising tool in pest control is the use of substances of plant origin with insecticidal properties, mainly in family farming and in organic farming systems. They are products considered to have a low environmental impact, as they are quickly degraded under the action of light, humidity, rain, and other abiotic factors. Therefore, studies related to alternative methods to suppress this pest that fit the integrated pest management it is extremely important. Studies that assess the efficiency of insecticides on eggs, one of the pest’s life stages with high vulnerability, are also fundamental to guide product rotation in management programs. To provide information on the management of this lepidopteran pest, the chemical insecticide cyantraniliprole (Benevia®), the biological B. thuringiensis subsp. kurstaki (Dipel®) and the hexane extract of Piper cubeba Linnaeus, 1753 (Piperales: Piperaceae). In this sense, we aimed to investigate a suitable substrate to maintain the rearing of this species in the laboratory, the action of insecticides on eggs and oviposition of P. xylostella, as well as the acute effect of lethal concentrations and the sublethal effects of chemical and biological insecticides and of P. cubeba plant extract. In addition to residual toxicity, as well as evaluating the phytotoxicity of the extract on collard green seedlings in a greenhouse and detached cabbage leaves kept in the laboratory. With this study, it was possible to verify that the adequate concentration of the extract of P. cubeba, which kills the pest in collard green without phytotoxicity in the leaves and seedlings of the plant, is 1%. By evaluating the biological parameters under the influence of sublethal concentrations (CL25 and CL10), it was found that insecticides caused changes in the larval and pupal period, pupae weight, and fecundity, in addition to changes in population growth. As for the action of insecticides on eggs and oviposition, the present study showed that the extract of P. cubeba presents higher toxic action on eggs and negatively influences the oviposition of P. xylostella. Regarding substrates, collard green leaf discs and collard green leaf discs on filter paper moistened with deionized water (control) showed to be the best substrates for P. xylostella oviposition, without loss in insect quality. Given these issues, it is expected that the results obtained in this thesis provide subsidies to help obtain quality insects for research, in addition to implementing alternatives aimed at controlling the diamondback moth.
Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), diamondback moth, is one of the main insect pest of crucifers worldwide, whose damage can seriously compromise the production of these vegetables. The most used method for its control is still the use of chemical products, in which synthetic insecticides are the most applied, due to their easy availability in the market and quick effect on larvae. However, the continuous insecticide applications for pest control, combined with P. xylostella biological factors, can contribute to the selection of resistant individuals. One of the alternatives to avoid or minimize chemical control is the use of bioinsecticides to control lepidopteran pests, such as those based on the entomopathogenic bacteria Bacillus thuringiensis Berliner. Another suitable option for Integrated Pest Management programs as a promising tool in pest control is the use of substances of plant origin with insecticidal properties, mainly in family farming and in organic farming systems. They are products considered to have a low environmental impact, as they are quickly degraded under the action of light, humidity, rain, and other abiotic factors. Therefore, studies related to alternative methods to suppress this pest that fit the integrated pest management it is extremely important. Studies that assess the efficiency of insecticides on eggs, one of the pest’s life stages with high vulnerability, are also fundamental to guide product rotation in management programs. To provide information on the management of this lepidopteran pest, the chemical insecticide cyantraniliprole (Benevia®), the biological B. thuringiensis subsp. kurstaki (Dipel®) and the hexane extract of Piper cubeba Linnaeus, 1753 (Piperales: Piperaceae). In this sense, we aimed to investigate a suitable substrate to maintain the rearing of this species in the laboratory, the action of insecticides on eggs and oviposition of P. xylostella, as well as the acute effect of lethal concentrations and the sublethal effects of chemical and biological insecticides and of P. cubeba plant extract. In addition to residual toxicity, as well as evaluating the phytotoxicity of the extract on collard green seedlings in a greenhouse and detached cabbage leaves kept in the laboratory. With this study, it was possible to verify that the adequate concentration of the extract of P. cubeba, which kills the pest in collard green without phytotoxicity in the leaves and seedlings of the plant, is 1%. By evaluating the biological parameters under the influence of sublethal concentrations (CL25 and CL10), it was found that insecticides caused changes in the larval and pupal period, pupae weight, and fecundity, in addition to changes in population growth. As for the action of insecticides on eggs and oviposition, the present study showed that the extract of P. cubeba presents higher toxic action on eggs and negatively influences the oviposition of P. xylostella. Regarding substrates, collard green leaf discs and collard green leaf discs on filter paper moistened with deionized water (control) showed to be the best substrates for P. xylostella oviposition, without loss in insect quality. Given these issues, it is expected that the results obtained in this thesis provide subsidies to help obtain quality insects for research, in addition to implementing alternatives aimed at controlling the diamondback moth.
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Palavras-chave
Extratos vegetais, Inseticidas, Plant extracts, Insecticides, Agricultura familiar