Phytochemical Screening and Bioactivity of Ludwigia spp. in the Control of Plutella xylostella (Lepidoptera: Plutellidae)

Antifeeding and Oviposition Deterrent Effect of Ludwigia spp. (Onagraceae) against Plutella xylostella (Lepidoptera: Plutellidae)

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.

Repellency and Reduction of Offspring Emergence Potential of Some Botanical Extracts against Sitophilus zeamais (Coleoptera: Curculionidae) in Stored Maize

Botanical repellents are, usually, considered safe to control Sitophilus zeamais, the main pest of stored maize, as they do not leave toxic residues in food, in addition to having lower costs than chemical insecticides. The aim of this study was to evaluate the repellency potential and the reduction of emerged offspring of botanical extracts, of Schinus terebinthifolius, Ludwigia sericea, L. tomentosa, L. nervosa, L. longifolia, and use them as botanical insecticides for S. zeamais. For the repellency test, arenas were set up, containing 50 g of maize kernels exposed to aqueous extract, besides a control treatment. At the center of each arena, 100 insects were released. After 48 h, the proportion of insects in the treated grains was determined. To test the effects of the extracts on insect mating and egg-laying, free-choice and no-choice tests were performed. Insects in both tests remained for ten days for mating and egg-laying. After this period, insects were removed to evaluate the offspring emergence. Sixty days after grain infestation, the number of emerged insects was counted. All selected botanical extracts demonstrated repellent action against S. zeamais, even after 48 h of application. The L. nervosa aqueous extract significantly reduced the emergence of S. zeamais.

Bioactivity of aqueous extract of Jacaranda spp. (Bignoniaceae) on Plutella xylostella L. 1758 (Lepidoptera: Plutellidae)

Abstract 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.

Cabbage Production in West Africa and IPM with a Focus on Plant-Based Extracts and a Complementary Worldwide Vision

In urban and peri-urban areas in West Africa, the cabbage Brassica oleracea L. (Brassicaceae) is protected using repeated high doses of synthetic insecticides. After a brief description of available IPM components, this paper presents a literature review focused on the botanical extracts that have been experimented with at the laboratory or in the field in West Africa against major cabbage pests. The literature reviewed mentions 19 plant species from 12 families used for cabbage protection in the subregion. The species most used are Azadirachta indica, Capsicum frutescens, Ocimum gratissimum and Ricinus communis. An overview of the world literature showed that a total of 13 plant species belonging to 8 families used to control cabbage pests are reported from the rest of Africa, and 140 plant species belonging to 43 families from the rest of the world. The most commonly used and tested plant species against insect pests in the three geographical areas considered is A. indica.