We tested the bioactivity of aqueous extracts of Ludwigia spp. (Myrtales: Onagraceae) on the biological cycle of Plutella xylostella. We assessed the duration of and viability during the larval, pupal and adult phases, as well as the influence of the extracts on the fecundity and hatching of P. xylostella eggs. Subsequently, we phytochemically screened the extracts. The extracts of L. tomentosa and L. longifolia reduced the pupal weight instead of prolonging the larval stage of P. xylostella. The L. tomentosa effect caused higher larval mortality and reduced the fecundity and hatching of P. xylostella eggs, and L. sericea reduced the egg survival. The phenolic compounds—flavonoids, condensed tannins and alkaloids—were more abundant in L. nervosa, L. tomentosa, L. sericea and L. longifolia. The L. tomentosa, L. longifolia and L. sericea extracts were bioactive, and these species showed the best results regarding their ability to control P. xylostella populations, because these plants produce substances able to inhibit food consumption and interfere with the morphological and physiological transformations of the offspring and the oviposition of adults.

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.

Plutella xylostella is the primary lepidopteran pest of Brassica crops due to its resistance to numerous insecticides. Multipesticide resistance in insects of agricultural importance is a global problem, and new methods of effective control that are less harmful to the environment are becoming increasingly necessary. The present study analyzed the effects of the aqueous extract of Simarouba sp. at concentrations of 10, 5, 1 and 0.1% in comparison with distilled water (as a control) on the feeding preference, oviposition, and embryonic development of P. xylostella. The results demonstrated that the aqueous extract of Simarouba sp. decreased oviposition and feeding in P. xylostella. A reduction in larval hatching was also observed, indicating ovicidal properties. In particular, the 1% concentration resulted in a more significant decrease in oviposition and the number of hatched larvae. Furthermore, concentrations of 10% and 5% caused food intake suppression, while concentrations of 1% and 0.1% reduced dietary intake by 97% and 78%, respectively. This study highlights the efficacy of Simarouba sp. aqueous extract in controlling the diamondback moth, as larval feeding and the number of individuals reaching the larval stage were reduced. Thus, the control method used in this laboratory study is expected to be successful if utilized on a large scale.

The flowers of plants of the genus Ludwigia are an important source of food for several species of bees. In the current study, we conducted an experiment with the aim to describe the reproductive biology and phenology of L. nervosa; to identify the species of visiting bees; analyze the foraging behavior of bees; and to investigate whether the reproductive success of the species is related to the foraging activity of bees. We found that the flowers received visits from several native bee species (n = 7), in addition of the exotic honey bees which came to be the dominant species. During visits the majority of the bees foraged in both resources, pollen and nectar. The significantly higher production of fruits in open pollinated pollination experiment compared to artificial cross pollination, suggests honey bees as effective pollinator of this plant species in the study site. Pollen deposition occurs efficiently, given the absence of pollen limitation. Despite massive visitation of honey bees, Ludwigianervosa is attractive to native bees, and therefore it may help to sustain population of both native and exotic pollinators in fragmented humid areas.

The use of botanical insecticides is a sustainable alternative for the regulation of Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) in brassica crops. Similarly, biological control with parasitoids can be an effective tool when integrated with bioinsecticides. However, the safety of natural insect enemies must be prioritized within pest control programs. The objective was to evaluate the effects of the water-based extracts of Serjania erecta Radlk (Sapindaceae) and Serjania marginata Casar (Sapindaceae), at 5% and 10% concentrations, on the reproduction of Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) in larvae of P. xylostella, topically treated with extracts. In addition, we evaluated the survival of adult females of T. howardi exposed to the respective extracts of Serjania spp. For this purpose, two bioassays were conducted. In the first, 4th instar larvae of P. xylostella were selected, and 20 μL of each treatment was applied topically (S. erecta 5%, S. erecta 10%, S. marginata 5%, S. marginata 10%, distilled water) in each larva and then exposed to T. howardi parasitism for 48 hours. The percentage of parasitism and emergence (%), life cycle length (days), total number of progeny, sex ratio and adult longevity were evaluated. In the second bioassay, the ASPECLE (Evaluation of Pesticide Selectivity under Extended Laboratory Conditions) system, adapted from the International Organization for Biological Control (IOBC) standard model, was used. In this bioassay, five cabbage leaf disks were introduced in each glass cylinder of the ASPECLE system, duly treated with distilled water, aqueous extracts of S. erecta and S. marginata, at concentrations of 5% and 10%, or acephate. Subsequently, ten adult females of T. howardi were released in each cylinder and the system was activated. Parasitoid survival was evaluated for 24, 48, 72, 96 and 120 hours. The aqueous extracts of S. marginata and S. erecta at concentrations of 5% and 10% did not interfere in the parasitism of T. howardi on 4th instar larvae of P. xylostella. Field experiments should be developed to prove the negative effect of aqueous extracts of S. marginata and S. erecta on other biological characteristics of T. howardi. As a precaution, releases of T. howardi and sprays of aqueous extracts of S. marginata and S. erecta should be made at different times for the biological management of P. xylostella.

A bioprospecção de espécies vegetais para o desenvolvimento de bioinsetidas pode contribuir para o controle de populações de Plutella xylostella na cultura das brássicas. O objetivo desta pesquisa foi estudar o efeito dos extratos aquosos de Serjania erecta e Serjania marginata, nas concentrações 5 e 10%, sobre a oviposição de P. xylostella. Para isso, foram realizados dois testes: o primeiro consistiu em um teste sem chance de escolha, onde foi colocado em cada gaiola um disco de couve tratado e um casal de adultos de P. xylostella; o segundo consistiu em um teste com chance de escolha, onde foram colocados em cada gaiola quatro discos tratados (dois discos tratados com extrato vegetal e dois discos tratados com água destilada) e um casal de adultos de P. xylostella. O experimento de oviposição sem chance de escolha foi realizado em delineamento experimental inteiramente casualizado (DIC) em esquema fatorial duplo (3x2) com 15 repetições por tratamento e o experimento com chance de escolha em delineamento experimental inteiramente casualizado (DIC). Foram contabilizados, diariamente, o número de ovos (fecundidade) e o número de larvas recém-emergidas (fertilidade dos ovos) durante 10 dias e calculado a viabilidade dos ovos (%) e o Índice de Dissuasão de Oviposição (IDO). Os resultados indicaram o efeito dissuasor das duas espécies vegetais, com redução da fecundidade, fertilidade e viabilidade de ovos nos tratamentos com os extratos aquosos de S. erecta e S. marginata, nas concentrações 5% e 10%, sendo que a concentração 10% apresentou melhores resultados para o teste sem chance de escolha. Portanto, as duas espécies vegetais apresentaram ação inseticida, atuando na redução da fecundidade, fertilidade, viabilidade de ovos e na dissuasão de oviposição deste microlepidóptero, contribuindo para o seu controle em cultivos de hortaliças.