Anastrepha obliqua (Macquart, 1835) is an important pest of tropical fruits, especially Anacardiaceae and Myrtaceae, in the Americas. The objective of this study was to evaluate the influence of mineral films and biomaterials on the coloring of guava fruits (Psidium guajava L.) and implications for the oviposition of A. obliqua. Before the bioassays, color, firmness characteristics, total soluble solids, pH, and titratable acidity were determined to characterize the maturation stage of the fruits. Pieces of guava fruit covered in aluminum foil were immersed in suspensions of mineral particles (Surround® WP kaolin; kaolins 605, 607, 608, and 611; and talc) and biomaterials (chitosan, cassava and potato starch, and guar gum) and distilled water (control). After drying, the fruits were exposed to two A. obliqua pairs for 48 h in choice and non-choice tests, and the numbers of eggs per fruit were counted. Mineral films (Surround® WP kaolin, and kaolins 605, 607, 608, and 611) and biomaterials (cassava and potato starch) interfered with the color of guava (luminosity, chroma, and hue angle), inhibiting the oviposition of A. obliqua. Talc, chitosan, and guar gum did not influence the oviposition of A. obliqua in guava.
BACKGROUND: Coffee (Coffea arabica L.) is one of the main commodities produced in Brazil. Insecticides like the (systemic) neonicotinoid thiamethoxam are widely used to suppress pest populations during coffee production, in particular the Neotropical leaf miner (Leucoptera coffeella Guérin-Mèneville & Perrottet, 1842) (Lepidoptera: Lyonetiidae). In addition to its efficacy against this pest species, thiamethoxam is also thought to be a bioactivator of plant metabolism, but has not yet been tested for such activity. Thus, the objectives of the present study were (1) to assess the concentration-response effects of thiamethoxam on the vegetative vigor of coffee seedlings (C. arabica 'Catuaí 144' cultivar) at different concentrations [2, 20, 40, 80 and 200 mg active ingredient (a.i.) kg −1 ] applied via soil drenching and (2) to evaluate if the plant response interferes with the effectiveness of thiamethoxam in controlling leaf miner populations. The morphophysiological traits of the coffee seedlings were evaluated 20, 40, 60 and 80 days after application, and leaf miner infestations were recorded starting 20 days after the insecticide application with the releasing of adults, and every 20 days afterwards. RESULTS:The results indicated that thiamethoxam has a deleterious effect on the morphophysiological traits of the plants compromising their development with increase in concentrations. However, leaf area exhibited a different pattern with a peak at 50 mg a.i. kg −1 consistent with thiamethoxam-induced hormesis (i.e. biphasic response with stimulatory effect at sublethal range of a toxic substance at the higher concentration). Nonetheless, such bioactivator effect did not affect thiamethoxan effectiveness against the leaf miner even at the lowest concentration tested. CONCLUSION: Thiamethoxan exhibited bioactivation effect on leaf at low concentration, but without compromising efficacy against leaf miner populations. Therefore, its proposed metabolism-boosting properties may encourage the unnecessary use of this insecticide, potentially leading to higher selection for insecticide resistance and an eventual decline in its effectiveness against the Neotropical leaf miner.
Resumo A canafístula é uma espécie nativa da América do Sul que possui grande potencial econômico para o setor florestal brasileiro, sendo muito utilizada em projetos de recuperação de áreas degradas e também em arborização urbana. No entanto, estudos relacionados às características morfológicas de frutos e sementes de canafístula são incipientes. Assim, objetivou-se com este trabalho, caracterizar biometricamente os frutos e as sementes de canafístula. O estudo foi conduzido no Laboratório de Tecnologia e Produção de Sementes da Universidade Estadual do Sudoeste da Bahia-UESB. Os frutos foram coletados em árvores matrizes localizadas na área rural de Caculé, BA, e separados de acordo com o número de sementes, obtendo-se dois lotes, com 100 unidades cada, um contendo apenas frutos com duas sementes e outro contendo frutos com apenas uma semente em seu interior. As sementes foram extraídas manualmente dos frutos e separadas quanto à posição dentro do fruto no caso de sementes provenientes de frutos com duas sementes, e outro lote de sementes foi obtido de frutos que continham apenas uma semente, formando assim três lotes diferentes com 100 de sementes (posição distal, posição proximal e semente única no fruto). As características analisadas para frutos e sementes foram: comprimento longitudinal, largura, espessura e massa fresca. Os dados obtidos foram submetidos à estatística descritiva, distribuição de frequências e cálculos de coeficiente de correlação de Pearson (r) à p-valor < 0,05. Os frutos de canafístula independentemente do número de sementes apresentam variabilidade para a maioria das características avaliadas, enquanto as sementes, tanto as distais, proximais ou
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