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At least 163 records · Page 9Linked to original sources
PubMed1998

Toxicity and Pathogenicity Testing of the Insect Pest Control Fungus Metarhizium anisopliae

Renewed interest in the use of Metarhizium anisopliae and its toxins for insect control prompted the following safety assessment. A neutral extract (methylene chloride, pH 7.2), derived from M. anisopliae cultures, was evaluated for toxicity and mutagenicity using aquatic animal bioassays and the Ames test. The average LC50 of the neutral extract obtained in static, acute 96-h tests conducted with </=24-h-old Mysidopsis bahia was 2.41 mg L-1. By partially purifying destruxins from the neutral extract, it was shown that destruxins alone were not responsible for the observed toxicity in mysids. The neutral extract was fetotoxic to developing grass shrimp, Palaemonetes pugio, and frog, Xenopus laevis, embryos; the LC50 values were 52 and 32 mg L-1, respectively. Eye spot abnormalities were observed in shrimp and frog embryos exposed to the neutral extract. In extract-exposed frog embryos, moderate to severe cranial, facial, and gut malformations were also observed. The neutral extract was toxic to juvenile mosquito fish, Gambusia affinis, at an LC50 value of 141 mg L-1. Adult female G. affinis surviving a 24-h exposure to 200 µg ml-1 of the neutral extract produced healthy broods. After 3 months, no mortalities or adverse effects were observed in adult G. affinis fed a diet partially composed of a freeze-dried M. anisopliae culture. The neutral extract did not show mutagenicity in the Ames test using strains TA98 and TA100 with and without metabolic activation by rat liver S9. Significant (p </= 0.05) mortalities were obtained when embryos of grass shrimp and inland silverside fish, Menidia beryllina, were exposed to the same lot of M. anisopliae conidiospores. Exposure of frog embryos to M. anisopliae conidiospores did not cause significant (p > 0.05) mortalities or malformations.

Journal Article↗
PubMed2006

Transgenic tobacco plants producing caffeine: a potential new strategy for insect pest control.

Caffeine (1,3,7-trimethylxanthine) is one of the most widely used plant secondary metabolites, primarily as a stimulant and an ingredient in drugs. In nature, caffeine is believed to function in chemical defense, acting as an antiherbivory and allelopathic agent, and therefore it might be employed to protect agriculturally important crop plants. In coffee plants, caffeine is synthesized from the precursor xanthosine in four steps, three N-methylations and removal of ribose. We had previously isolated genes encoding three distinct N-methyltransferases, and we demonstrated production of recombinant enzymes that yielded caffeine in in vitro reconstitution experiments. When these caffeine biosynthetic pathway genes were simultaneously expressed in tobacco plants (Nicotiana tabacum), caffeine was successfully produced up to 5 microg/g fresh weight in leaves. The leaves were unpalatable to tobacco cutworms (Spodoptera litura). This repellent action appeared to be more widely applicable to lepidopteran caterpillars as observed with small white (Pieris rapae) fed on Chinese cabbages that had been top-treated with caffeine. Our recent results suggest a novel approach to strengthen anti-herbivore traits by producing caffeine in crop plants.

Animals↗
PubMed2004

Fusion proteins containing insect-specific toxins as pest control agents: snowdrop lectin delivers fused insecticidal spider venom toxin to insect haemolymph following oral ingestion.

The mannose-specific snowdrop lectin (Galanthus nivalis agglutinin: GNA), when fed to insects, binds to the gut epithelium and passes into the haemolymph. The ability of GNA to act as a carrier protein to deliver an insecticidal spider venom neurotoxin (Segestria florentina toxin 1: SFI1) to the haemolymph of lepidopteran larvae was investigated. Constructs encoding SFI1 and an SFI1/GNA fusion protein were expressed in Pichia pastoris. The insecticidal activity of purified recombinant proteins on injection was found to be comparable to published values for SfI1 purified from spider venom [Toxicon 40 (2002) 125]. Whereas neither GNA nor SFI1 alone showed acute toxicity when fed to larvae of tomato moth (Lacanobia oleracea), feeding SFI1/GNA fusion at 2.5% of dietary proteins was insecticidal to first stadium larvae, causing 100% mortality after 6 days. The protein also showed a significant, dose dependent, toxicity towards fourth and fifth stadium larvae, with growth reduced by up to approximately 90% over a 4-day assay period compared to controls. Delivery of intact SFI1/GNA to the haemolymph in these insects was shown by western blotting; haemolymph samples from fusion-fed larvae contained a GNA-immunoreactive protein of the same molecular weight as the SFI1/GNA fusion. SFI1/GNA and similar fusion proteins offer a novel and effective approach for delivering haemolymph active toxins by oral administration, which could be used in crop protection by expression in transgenic plants.

Animals↗
PubMedDate not supplied

Monitoring Ontario-grown apples for pest control chemicals used in their production, 1978-86.

Between 1978 and 1986, 305 samples of apples were monitored for the residues of a wide range of pesticides used in their production. Three (1%) contained residues above the maximum residue limits (MRL) permitted under the Canadian Food and Drug Act and regulations; two involved phosalone at 5.9 and 6.2 mg/kg respectively and one involved diphenylamine at 6.7 mg/kg when the MRL was 5.0 mg/kg for both compounds. Low residues of dicofol, endosulfan, phosalone, phosmet, captan, daminozide and diphenylamine were frequently found; however they were well below the MRLs. These residue levels were correlated with survey data on the areas of the apple crop treated with specific pesticides. Residues of carbaryl, diazinon, ethion, azinophosmethyl, parathion, and dithiocarbamate fungicides were found occasionally; all were well below the MRLs and correlated with the pattern of use. No residues of PCB were found to a limit of detection of 0.01 mg/kg.

Environmental Monitoring↗
PubMed2005

Use of novel compounds for pest control: insecticidal and acaricidal activity of essential oil components from heartwood of Alaska yellow cedar.

Laboratory bioassays were conducted to determine the activity of 15 natural products isolated from essential oil components extracted from the heartwood of Alaska yellow cedar, Chamaecyparis nootkatensis (D. Don) Spach., against Ixodes scapularis Say nymphs, Xenopsylla cheopis (Rothchild), and Aedes aegypti (L.) adults. Four of the compounds from the essential oil have been identified as monoterpenes, five as eremophilane sesquiterpenes, five as eremophilane sesquiterpene derivatives from valencene and nootkatone, and one as a sesquiterpene outside the eremophilane parent group. Carvacrol was the only monoterpene that demonstrated biocidal activity against ticks, fleas, and mosquitoes with LC50 values after 24 h of 0.0068, 0.0059, and 0.0051% (wt:vol), respectively. Nootkatone from Alaska yellow cedar was the most effective of the eremophilane sesquiterpenes against ticks (LC50 = 0.0029%), whereas the nootkatone grapefruit extract exhibited the greatest biocidal activity against fleas (LC50 = 0.0029%). Mosquitoes were most susceptible to one of the derivatives of valencene, valencene-13-aldehyde (LC50 = 0.0024%), after 24 h. Bioassays to determine residual activity of the most effective products were conducted at 1, 2, 4, and 6 wk after initial treatment. Residual LC50 values for nootkatone did not differ significantly at 4 wk posttreatment from the observations made at the initial 24-h treatment. The ability of these natural products to kill arthropods at relatively low concentrations represents an alternative to the use of synthetic pesticides for control of disease vectors.

Aedes↗