No abstract

Plants produce a wide variety of bioactive compounds with insecticidal properties, such as secondary metabolites capable of interfering with the nutrition and reproduction of pest species such as Plutella xylostella. Thus, the objective of this study was to evaluate the effects of aqueous and ethanolic extracts of Ludwigia spp. (Onagraceae) on the feeding and oviposition of P. xylostella. Choice bioassays were performed using aqueous and ethanolic extracts. The aqueous extract of L. tomentosa resulted in an approximately 81% reduction in larval feeding compared to that in the control, with an antifeedant index (AI) of 52%. The aqueous and ethanolic extract of L. nervosa acted by stimulating larval feeding. The oviposition was significantly reduced in the kale leaves treated with aqueous and ethanolic extracts of Ludwigia spp. The aqueous extracts promoted an average 90% reduction in oviposition when compared to that in the control, and an oviposition deterrent index (ODI) above 61% was classified as an oviposition deterrent. In addition, ethanolic extracts affected 81% of oviposition, with an ODI above 41%. Bioassays should be performed to clarify the use of aqueous and ethanolic extracts of L. nervosa as they acted as phagostimulants in the feeding tests and as deterrents in the oviposition tests. The phenolic compounds—flavonoids, condensed tannins, and alkaloids—were more abundant in L. nervosa, L. tomentosa, L. sericea, and L. longifolia. The extracts of L. longifolia and L. tomentosa showed the best results, interfering with the host choice for feeding and oviposition in P. xylostella and representing an alternative for the control of diamondback moths.

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.

The feeding activity of Plutella xylostella in brassica crops can lead to large losses; thus, pesticides that prevent feeding during the larval stage or prevent the metamorphosis of this insect can be used for its control. In this study, the effects of two types of aqueous extracts of Tradescantia pallida on the different life stage of P. xylostella cycle were tested; neither of the two aqueous extracts, which were obtained by infusion and maceration, had been tested against P. xylostella. The biological variables evaluated were larval and pupal duration and viability, pupal weight, sex ratio, longevity of females, fecundity, fertility and oviposition period. There was no significant difference in the duration of the larval phase of P. xylostella between the bioassay treatments; however, larval viability was lower when the individuals were exposed to both types of T. pallida extracts. Reduced pupal viability was observed among the individuals treated with the application of the extracts. Treatment with the aqueous extract obtained by infusion caused the lowest pupal weight, fecundity, and fertility and longevity among females. The results obtained in this study allow us to propose the bioextract as an alternative for pest management, emphasizing the technique for small producers and/or organic.

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.

Sustainability in food production is an increasingly discussed issue nowadays; therefore, demands for research that can reduce production costs and ensure the quality and autonomy of production are relevant, with attention to the use of plants due to their importance in biodiversity. Thus, the objective of this research was to evaluate the bioactivity, feeding preference, and oviposition preference of Miconia albicans botanical extracts at concentrations of 1%, 5%, and 10% against Plutella xylostella. We observed reduced larval duration, larval survival, female hatching success, and repellence of oviposition and feeding for all concentrations. For higher concentrations, the extracts showed a larval mortality rate of 58%, a feeding reduction of 82%, and an oviposition reduction of 94%, showing potential for pest control. Phytochemical analyses identified phenolic compounds, flavonoids, and tannins, which are substances with repellent and larvicidal properties. This is the first report on the phytosanitary potential of M. albicans, showing that the plant has both lethal and sublethal effects on P. xylostella.

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.