Search results for "insecticides"
showing 10 items of 166 documents
Insecticidal Activity and Synergistic Combinations of Ten Different Bt Toxins against Mythimna separata (Walker)
2018
The oriental armyworm (OAW), Mythimna separata (Walker), is a destructive pest of agricultural crops in Asia and Australia. Commercialized Bt crops have performed very well against their target pests
Binding Site Alteration Is Responsible for Field-Isolated Resistance to Bacillus thuringiensis Cry2A Insecticidal Proteins in Two Helicoverpa Species
2010
Background Evolution of resistance by target pests is the main threat to the long-term efficacy of crops expressing Bacillus thuringiensis (Bt) insecticidal proteins. Cry2 proteins play a pivotal role in current Bt spray formulations and transgenic crops and they complement Cry1A proteins because of their different mode of action. Their presence is critical in the control of those lepidopteran species, such as Helicoverpa spp., which are not highly susceptible to Cry1A proteins. In Australia, a transgenic variety of cotton expressing Cry1Ac and Cry2Ab (Bollgard II) comprises at least 80% of the total cotton area. Prior to the widespread adoption of Bollgard II, the frequency of alleles conf…
Proposed use of spatial mortality assessments as part of the pesticide evaluation scheme for vector control
2013
Background: The WHO Pesticide Evaluation Scheme to evaluate the efficacy of insecticides does not include the testing of a lethal effect at a distance. A tool was developed to evaluate the spatial mortality of an insecticide product against adult mosquitoes at a distance under laboratory and field conditions. Operational implications are discussed. Methods: Insecticide paint, Inesfly 5A IGR (TM), containing two organophosphates (OPs): chlorpyrifos and diazinon, and one insect growth regulator (IGR): pyriproxyfen, was the product tested. Laboratory tests were performed using "distance boxes" with surfaces treated with one layer of control or insecticide paint at a dose of 1 kg/6 sq m. Field …
Determination of acetylcholine, nitrostigmine and acetylcholinesterase activity in four patients with severe nitrostigmine (E 605 forte) intoxication.
1974
Concentrations of acetylcholine and nitrostigmine as well as acetylcholinesterase activity were determined in 4 patients with severe nitrostigmine intoxication. In the acute phase of the intoxication, acetylcholine levels up to 36 and 55 ng/ml were found in blood plasma and cerebrospinal fluid, respectively. At the same time no activity of acetylcholinesterase in plasma and erythrocytes was detected. Acetylcholinesterase activity gradually recovered at the end of the second week. In the first 3 days after the ingestion plasma nitrostigmine concentrations ranged from 409 to 86 ng/ml. At the end of the third week nitrostigmine was still found in a concentration of about 1 ng/ml plasma. Redist…
Susceptibility of Grapholita molesta (Busck, 1916) to formulations of Bacillus thuringiensis, individual toxins and their mixtures.
2016
The Oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae), is a major pest of fruit trees worldwide, such as peach and apple. Bacillus thuringiensis has been shown to be an efficient alternative to synthetic insecticides in the control of many agricultural pests. The objective of this study was to evaluate the effectiveness of B. thuringiensis individual toxins and their mixtures for the control of G. molesta. Bioassays were performed with Cry1Aa, Cry1Ac, Cry1Ca, Vip3Aa, Vip3Af and Vip3Ca, as well as with the commercial products DiPel® and XenTari®. The most active proteins were Vip3Aa and Cry1Aa, with LC50 values of 1.8 and 7.5ng/cm2, respectively. Vip3Ca was nontoxic to this …
Tribolium castaneum Apolipophorin-III acts as an immune response protein against Bacillus thuringiensis Cry3Ba toxic activity
2013
In this study, a 2.1-fold Apolipophorin-III mRNA up-regulation was found in Tribolium castaneum larvae challenged with Bacillus thuringiensis Cry3Ba spore-crystal mixture. Knockdown of Apolipophorin-III by RNAi resulted in increased T. castaneum larvae susceptibility following Cry3Ba spore-crystal treatment, demonstrating Apolipophorin-III involvement in insect defense against B. thuringiensis. We showed that Apolipophorin-III participates in T. castaneum immune response to B. thuringiensis activating the prophenoloxidase cascade since: (i) phenoloxidase activity significantly increased after Cry3Ba spore-crystal treatment compared to untreated or Cry1Ac spore-crystal treated larvae and (ii…
Reduced membrane-bound alkaline phosphatase does not affect binding of Vip3Aa in a Heliothis virescens resistant colony
2020
The Vip3Aa insecticidal protein from Bacillus thuringiensis (Bt) is produced by specific transgenic corn and cotton varieties for efficient control of target lepidopteran pests. The main threat to this technology is the evolution of resistance in targeted insect pests and understanding the mechanistic basis of resistance is crucial to deploy the most appropriate strategies for resistance management. In this work, we tested whether alteration of membrane receptors in the insect midgut might explain the >
Relationship between esterase activity and acrinathrin and methiocarb resistance in field populations of western flower thrips, Frankliniella occiden…
2006
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…
Non-neuronal acetylcholine involved in reproduction in mammals and honeybees.
2017
Bacteria and archaea synthesize acetylcholine (ACh). Thus, it can be postulated that ACh was created by nature roughly three billion years ago. Therefore, the wide expression of ACh in nature (i.e., in bacteria, archaea, unicellular organisms, plants, fungi, non-vertebrates and vertebrates and in the abundance of non-neuronal cells of mammals) is not surprising. The term non-neuronal ACh and non-neuronal cholinergic system have been introduced to describe the auto- and paracrine, that is, local regulatory actions of ACh in cells not innervated by neuronal cholinergic fibers and to communicate among themselves. In this way non-neuronal ACh binds to the nicotinic or muscarinic receptors expre…
Toxicity of Dimethoate to Some Soil Animal Species in Different Soil Types
1996
Toxicity of dimethoate (insecticide) to an earthworm (Aporrectodea caliginosa tuberculata), a collembola (Folsomia candida), and an enchytraeid worm (Enchytraeus crypticus/variatus) was studied in three different soil types (artificial soil, clayey soil, and humus sandy soil). Parameters measured were survival and biomass change of the earthworms and survival and reproduction of the collembolas and enchytraeids. The degradation of dimethoate was analyzed too. Toxic effects were observed at the concentrations of some mg/kg dry soil. The biomass reduction of the earthworms occurred at lower concentrations than reduction in survival. The collembolas were more susceptible to dimethoate than the…