Extratos botânicos com propriedades inseticidas buscam minimizar os problemas provocados pelo uso incorreto e muitas vezes exagerado dos agrotóxicos. Dependendo da concentração utilizada e do método de extração, certos extratos podem provocar diversas reações sobre os insetos-daninhos. Sendo assim, o presente trabalho teve por objetivo avaliar a toxicidade dos extratos aquosos elaborados por maceração e infusão de Psychotria capillacea, Psychotria deflexa e Psychotria leiocarpa sobre ovos, larvas e pupas de Plutella xylostella. Foram utilizados sete tratamentos para avaliar a toxicidade dos extratos, sendo: 1) infusão P. capillacea, 2) infusão de P. deflexa, 3) infusão de P. leiocarpa, 4) maceração P. capillacea, 5) maceração de P. deflexa, 6) maceração de P. leiocarpa e 7) água destilada (controle). Larvas de terceiro instar de P. xylostella e pupas com até três dias de formação receberam aplicação tópica dos tratamentos, enquanto fragmentos de couve contendo ovos desse inseto foram imersos nos tratamentos. Os resultados demonstraram que os extratos aquosos por infusão e maceração de P. capillacea e P. leiocarpa e P. deflexa não apresentaram toxicidade significativa sobre as larvas e pupas de P. xylostella, enquanto extratos elaborados por maceração reduziram a sobrevivência de ovos desse inseto. Observou-se que os extratos macerados causaram a mortalidade nas primeiras 46 horas e as infusões foram mais efetivas após esse período. Sendo assim, outros testes devem ser realizados para elucidar a eficiência dos extratos de Psychotria sobre os parâmetros biológicos e comportamentais de P. xylostella, tendo em vista que novas técnicas de extração devem ser exploradas.
Tropaeolum majus L. species produce flowers with all sorts of colors, from yellow to red. This work aimed to apply optical fluorescence spectroscopy to study bee abundance in T. majus, answering the following questions: (1) do corolla temperature and weather conditions affect the abundance of visiting bee species? (2) do flower color and corolla fluorescence affect the abundance of visiting bee species? (3) do red flowers attract more visiting bees? (4) is there a relationship between bee visits and flower compounds? The bee species Apis mellifera, Paratrigona lineata, and Trigona spinipes were the most observed in T. majus flowers. The latter was more active in the morning and preferred orange and yellow flowers. These colors also had higher temperatures and fluorescence emissions than did the red ones and those with yellow-red and orange-red nectar guides. Orange flowers emitted a broadband UV spectrum (between 475 and 800 nm). This range might be due to compounds such as hydroxycinnamic acid, flavonols, isoflavonoids, flavones, phenolic acid, and chlorophyll. Extracts from different T. majus corolla colors showed that flowers emit specific fluorescent signals, mainly related to bee color vision and learning, thus acting as a means of communication between bees and flowers. In this way, this information evidences the interaction between bees and T. majus flowers, allowing conservation actions for pollinators.
The high consumption rate of vegetables stimulates the cultivation and increases the demand regarding the adequacy of the production processes. The attack of the pest Plutella xylostella causes high losses by reducing product quality, typifying a phytosanitary problem. This study aimed to verify the bioactivity of aqueous extracts of leaves of Jacaranda decurrens and Jacaranda mimosifolia at concentrations of 5, 10, and 15% on the insect. The choice test was carried out at the laboratory to determine the food effect of plant extracts and evaluate changes in the life cycle of insects exposed to active compounds through the analysis of biological parameters. Plant extracts of J. decurrens and J. mimosifolia presented with phagodeterrent classification in the choice experiments. The three J. decurrens extract concentrations promoted a prolongation of larval and pupal duration, while the duration of individuals treated with J. mimosifolia at 10% was significantly reduced. Occurred reduction in larval survival of individuals treated with aqueous extracts of J. decurrens and J. mimosifolia. Eggs from treatments with aqueous extract of J. decurrens and J. mimosifolia had reduced survival. Pupal survival of individuals treated with extract at 15% showed a significant reduction compared to the treatments at 5% and 10%. Pupae from the treatment with aqueous extract of Jacaranda mimosifolia showed a reduction in biomass in the treatment at 15% differing from the control e 5%. Thus, the aqueous extracts of the species J. decurrens and J. mimosifolia show insecticidal potential in the tests performed on P. xylostella.
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