RESUMO
Colorado Potato Beetle (CPB) is one of the most destructive potato pests that can quickly develop resistance to insecticides. Therefore, new safe and effective control strategies that are less susceptible to the development of resistance by CPB are urgently needed. Due to their complex mode of action, the likelihood of resistance development by target pests is generally low with antifeedants. In the present study, we assessed the effect of secondary metabolites of various Xenorhabdus bacteria species and strains on CPB adult feeding and on larval development. The metabolites were applied in the form of cell free supernatants (CFSs) from Xenorhabdus cultures. In bioassay 1, leaves treated with ten Xenorhabdus cultures were fed to CPB adults, and their feeding was assessed daily for one week. In bioassay 2, CPB egg masses were placed on the leaves treated with five bacterial cultures, and larval development to pupae was monitored. Out of the ten Xenorhabdus cultures tested, two strains exhibited a significant reduction in the feeding behavior of Colorado Potato Beetle adults, with reductions of up to 70% compared to the control. The effect of CFSs on larval development was variable, and when treated with X. khoisanae SGI 197, over 90% of larvae died in the first few days before reaching the 2nd instar, and complete mortality was achieved on the 8th day of the experiment. Our study is the first study to demonstrate the antifeedant effect of Xenorhabdus cultures towards herbivorous beetles, and the metabolites of these bacteria may have potential for CPB control. Clearly, the metabolites produced by X. khoisanae SGI-197 may be a promising tool for CPB larvae control with the potential to significantly decrease damage to potato plants.
Assuntos
Besouros , Solanum tuberosum , Xenorhabdus , Animais , Larva , BactériasRESUMO
The cotton leafworm, Spodoptera littoralis (Bosid.), is a major pest in African and Asian nations that attacks a wide variety of host plants. This study was conducted to assess the effectiveness of effective microorganisms (EMs) on the biological and physiological features of S. littoralis larvae. Five concentrations (100, 200, 300, 400, and 500 ppm) of EMs were tested. Antifeedant activity, food consumption index, the efficiency of converting digested food, the efficiency of converting ingested food, relative growth rate, and approximate body tissue of the fourth larval instar of S. littoralis were determined. Moreover, carbohydrate enzyme activities (amylase, trehalose, and invertase), total protein, and total lipids of S. littoralis larvae were measured to elucidate the mode of action of the tested agent in the S. littoralis's larval stage. The EMs at 500 ppm had a substantial impact on antifeedant activity, nutritional indices, egg deposit reduction, and hatchability in S. littoralis during the five days. All concentrations interrupted S. littoralis's life cycle and developmental phases. Furthermore, all concentrations were quite useful in lengthening the developmental stages of S. littoralis. In addition, Ems affected the biochemical activities of larvae, leading to disturbances in carbohydrate, lipid, and protein levels. From this study, EMs can be used as a bioinsecticide alternative to traditional insecticides against S. littoralis and may be compatible with integrated pest management approaches.
RESUMO
Red clover (Trifolium pratense L.) is a perennial plant widely used as a forage resource for several animals. This plant is the exclusive host of Hylastinus obscurus (Marsham) which causes irreparable damages to the root system affecting their persistence. It has been reported that the presence of the isoflavonoid formononetin in roots of red clover could act as an antifeedant on H. obscurus. There are not studies related to the formononetin content in red clover roots to the antifeedant effect elicited by experimental lines and cultivar of red clover. Six red clover genotypes were investigated in both formononetin content and their respective antifeedant action. The results showed to Sabtoron High and Superqueli-INIA with both the highest formononetin content in red clover roots and antifeedant effect, allowing to suggest that this secondary metabolites could be used as a chemical factor for red clover plants. Moreover, a rapid methodology for searching red clover genotypes with high formononetin content is reported.
El treÌbol rosado (Trifolium pratense L.) es una planta perenne ampliamente utilizada como fuente de forraje de variados animales. Esta planta es el exclusivo hospedero de Hylastinus obscurus (Marsham) el cual causa irreparables danÌos al sistema radical afectando seriamente su persistencia. Se ha reportado que la presencia del isoflavonoide formononetina en raiÌces del treÌbol rosado podriÌa actuar como antialimentario sobre H. obscurus. Actualmente no existen estudios que relacionen el contenido de formononetina en raiÌces de treÌbol rosado con el efecto antialimentario elicitado por liÌneas experimentales y cultivares de treÌbol rosado. Seis genotipos de esta leguminosa fueron evaluados en cuanto a su contenido de formononetina y actividad antialimentaria. Los resultados mostraron que los cultivares Sabtoron High y Superqueli-INIA presentaron altos niveles de formononetina en sus raiÌces y efecto antialimentario sobre H. obscurus, lo que permite sugerir que este metabolito secundario podriÌa ser usado como factor quiÌmico para incrementar la persistencia de plantas de treÌbol rosado. AdemaÌs, se informa una metodologiÌa raÌpida para la buÌsqueda de genotipos con altos contenidos de formononetina.
