0000000000219162
AUTHOR
Ana C Maymó
Relationship between esterase activity and acrinathrin and methiocarb resistance in field populations of western flower thrips, Frankliniella occidentalis.
The western flower thrips, Frankliniella occidentalis (Pergande), is a serious pest in the south-east of Spain owing to its direct feeding on crops, transmission of the tomato spotted wilt virus and its very high level of resistance to insecticides. Mechanisms of resistance were examined using field populations of F. occidentalis with different susceptibilities to acrinathrin, methiocarb (selective insecticides), endosulfan, metamidophos and deltamethrin (broad-spectrum insecticides). Esterase activity towards alpha-naphthyl acetate and p-nitrophenyl acetate in resistant strains was significantly higher than in the reference strain (MLFOM) for both model substrates. This higher activity was…
Vitellogenesis inhibition in Oncopeltus fasciatus females (Heteroptera: Lygaeidae) exposed to cadmium
Abstract Newly moulted females of the insect Oncopeltus fasciatus were exposed to cadmium (Cd) dissolved in the drinking water (50–400 mg l −1 Cd) for 5 days. Cd exposure delayed ovarian maturation and inhibited egg production. Exposure to Cd, moreover, decreased hemolymph levels of the two major vitellogenin polypeptides of O. fasciatus , VG1 and VG2, in a concentration-dependent way, probably by a reduction in their synthesis. The ovarian levels of VG1 and VG2 were also decreased in Cd-exposed females. It was next investigated whether Cd effects might be a consequence of the endocrine disruption of vitellogenin synthesis, which is controlled by juvenile hormone (JH). JH replacement therap…
Sequiterpene-related compounds as endocrine disrupters in Oncopeltus fasciatus, and potential reduced glutathione synthesis modifiers
Sesquiterpene lactones have been found to exhibit effects on insect growth and development. In this study, the bioactivity of natural lactones extracted from Centaurea mariolensis and some structurally related synthetic derivatives has been investigated. Assays have also been carried out in order to determine the potential of these lactones as modifiers of reduced glutathione (GSH) synthesis.
Evaluation of metabolic detoxifying enzyme activities and insecticide resistance inFrankliniella occidentalis
The western flower thrips Frankliniella occidentalis (Pergande) is a very significant pest of a number of different agricultural crops in the south-east of Spain. The importance of thrips as a pest is not due mainly to the direct damage inflicted on the plant, but to the loss in commercial value which occurs as a consequence of the development of dark spots caused by the tomato spotted wilt virus (TSWV) which they transmit. The economic threshold is therefore almost zero, which enhances the problems of resistance management. The present work is part of a global project that attempts to evaluate the status of insecticide resistance in field populations of thrips obtained from several agricul…
Vitellogenin polypeptide levels in one susceptible and one cadmium-resistant strain of Oncopeltus fasciatus (Heteroptera: Lygaeidae), and its role in cadmium resistance.
The heavy metal Cd has recently been shown to have endocrine disrupting activity in different vertebrate species. In the insect Oncopeltus fasciatus, Cd exposure delays ovarian maturation and inhibits vitellogenesis, probably through a reduction in vitellogenin (Vg) polypeptide synthesis. An O. fasciatus strain was selected in the laboratory for Cd resistance with gradually increasing Cd concentrations for 50 generations. Cd-selected (OCdR) insects were 2.7-2.3 times more resistant to chronic exposure to Cd than susceptible (OS) insects. OCdR females showed increased (up to 90%) Vg polypeptide levels in hemolymph. Vg polypeptide synthesis was equally decreased in OCdR and OS females after a…
Antioxidant Enzymes inOncopeltus fasciatus(Heteroptera: Lygaeidae) Exposed to Cadmium
Abstract Catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), and thiobarbituric acid reactive substances (TBARS) were measured together with cadmium (Cd) toxicity and accumulation in newly molted adults of Oncopeltus fasciatus (Dallas) exposed to the metal in drinking water. Insects were provided with either 200 or 20 mg Cd/liter (96-h LC30 and LC10, respectively) or with tap water for 1, 3, 5, and 7 d. Insects exposed to either concentration accumulated Cd in a time-dependent manner. Peroxilipids measured as TBARS were significantly elevated (1.7- to 1.9-fold) from day 3 in insects exposed to 200 mg Cd/liter, whereas TBARS levels of insects exposed to 20 mg Cd/lite…
Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)
Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg C…