RESUMO
BACKGROUND: White and colored fiber cotton cultivars have been developed to increase production and opportunities for family farming. The broad mite, Polyphagotarsonemus latus (Banks) is an important pest in cotton crops, nevertheless, different cotton cultivars may influence its host selection and population growth. For P. latus control, acaricides application is commonly performed, although less is known about the sublethal effects of these products. Thus, the host preference and instantaneous rate of increase (ri ) of P. latus were evaluated on white and colored cotton cultivars, as well as the lethal and sublethal effects of acaricides through mortality tests and population growth. RESULTS: In free-choice tests to evaluate host preference among white and colored cotton cultivars, no preference was observed for P. latus. The instantaneous ri values were positive for all tested cultivars, however, differences were observed between the colored BRS Rubi and the white BRS 201. The population growth of P. latus decreased with increasing concentrations of the acaricides abamectin, spirodiclofen, azadirachtin and spiromesifen. Nevertheless, azadirachtin and spiromesifen presented positive ri values even at the highest lethal concentrations (LC90 ), while abamectin and spirodiclofen provided negative ri values of P. latus from LC90 and LC70 , respectively. CONCLUSION: No host preference of P. latus was observed among white and colored cotton cultivar. Abamectin and spirodiclofen presented relevant sublethal effects that should be considered for the integrated management of this pest.
Assuntos
Acaricidas , Ácaros , Acaricidas/farmacologia , Animais , Gossypium , Crescimento DemográficoRESUMO
The red spider mite, Tetranychus neocaledonicus (Acari: Tetranychidae) can be an important pest on lima bean (Phaseolus lunatus L.). Thus, the objective of this work was to assess the antibiosis and antixenosis effects of lima bean genotypes on T. neocaledonicus, through the evaluation of performance parameters as well as the host preference for food and oviposition. Nine lima bean genotypes from the Active Bank of Germplasm of the Federal University of Piauí - BGP / UFPI were screened. To assess antibiosis parameters, eggs of T. neocaledonicus were individually placed on leaf disks of each genotype. The period and survival of the different stages of development (larvae, protonymph, deutonymph and adult), pre-oviposition, oviposition and post-oviposition period, longevity and fecundity of females were evaluated, and fertility life table parameters were calculated. In choice tests, adult females of T. neocaledonicus were used. The numbers of mites and eggs were counted for each genotype. The protonymph, egg-adult, longevity and oviposition period, fertility life table parameters, as well as the food and oviposition preference were affected by lima bean genotypes. We found that some genotypes reduced adult female longevity, increased the larval and egg-adult period, decreased oviposition period, negatively affected the fertility life table parameters, reducing the net reproductive rate (Ro), the intrinsic rate of increase (rm) and the finite rate of increase (λ), while increasing the population doubling time (DT), exhibiting a reliable antibiosis effect upon T. neocaledonicus. Nevertheless, these same genotypes were the most preferred for food and oviposition. By contrast, some other genotypes reduced the adult female longevity and oviposition period, elongated the larval period and affected fertility life table parameters, demonstrating an antibiosis effect upon T. neocaledonicus. Moreover, these other genotypes were among the less preferred for food and oviposition, exhibiting an additional antixenosis effect. Thus, our results demonstrate that the genotypes of lima bean may present distinct levels of resistance to T. neocaledonicus, and this resistance may be an important tool for Integrated Pest Management. This is one of the first studies aiming to describe mite resistance sources in lima bean.
RESUMO
The insecticide Match® (lufenuron), one of the main insect growth regulators used in pest control, has been presented as a viable alternative against the boll weevil, Anthonomus grandis (Coleoptera: Curculionidae), by inhibiting chitin synthesis. Thus, this study aimed to examine whether Match® interferes in the synthesis of the peritrophic matrix, leading to changes in the midgut epithelium, resulting in nutritional deficiency and reflecting, thereby, in the gametogenesis process of A. grandis. Floral cotton buds were immersed in the insecticide solution (800µL of Match®+200mL of distilled water) and offered to the adult insects. The midguts of the insects were evaluated after 24 and 120h after feeding. The gonads were evaluated after 120h. The results showed that Match®, in both evaluation periods, induced histopathological alterations such as disorganization, vacuolization and desquamation of the midgut epithelium; histochemical modifications in the distribution patterns of carbohydrates, although without quantitative changes; and a strong decrease in protein levels. No apoptosis were observed, however, there was an increase in the number of regenerative cell nests. In the testicles, a reduction in the amount of spermatozoids and reduced carbohydrate levels were observed, but no difference in protein levels. The ovarioles presented structural disorganization of follicular cells, yolk reduction and decrease in protein levels, however, no change in carbohydrates levels was noted. Therefore, it is concluded that Match® performs histopathologic and histochemical alterations in the midgut epithelium and the gonads of A. grandis adults, reflecting in the gametogenesis process, presenting itself as a promising tool in the management of this pest on cotton crops.
Assuntos
Benzamidas , Sistema Digestório/efeitos dos fármacos , Gametogênese/efeitos dos fármacos , Inseticidas , Gorgulhos/fisiologia , Animais , Apoptose/efeitos dos fármacos , Sistema Digestório/patologia , Feminino , Imuno-Histoquímica , Masculino , Ovário/efeitos dos fármacos , Ovário/crescimento & desenvolvimento , Ovário/patologia , Testículo/efeitos dos fármacos , Testículo/crescimento & desenvolvimento , Testículo/patologia , Gorgulhos/crescimento & desenvolvimentoRESUMO
Spodoptera frugiperda is a polyphagous insect that causes economic losses to several crops in Brazil and is the major obstacle to corn production. Researches focusing on alternative control, e.g. botanical products are expanding to offer a wide variety of molecules that interfere with different biological parameters of insect pests. Thus, this study tested the hypothesis that clove essential oil affects the spermatogenesis, ovarioles histochemistry and the fertility of S. frugiperda. The results showed that clove essential oil affects the gametogenesis of S. frugiperda ovarioles, reflecting negatively on its reproduction, proving to be a promising tool for controlling this pest.
Spodoptera frugiperda es un insecto polífago que causa pérdidas económicas a varias cosechas en Brasil y es el mayor obstáculo para la producción de maíz. Este estudio está centrado en el control alternativo, con productos botánicos que se están expandiendo y ofrecen una amplia variedad de moléculas que interfieren con diferentes parámetros biológicos de plagas de insectos. Por tanto, se puso a prueba la hipótesis de que el aceite esencial de clavo de olor afecta la espermatogénesis. La histoquímica de los ovarioles y la fertilidad de S. frugiperda. Los resultados mostraron que el aceite esencial de clavo de olor afecta la gametogénesis de los ovarioles en S. frugiperda, lo que incide negativamente en su reproducción, demostrando ser una herramienta prometedora para el control de esta plaga.