Search results for "Larva"
showing 10 items of 632 documents
Susceptibility of Spodoptera frugiperda and S. exigua to Bacillus thuringiensis Vip3Aa insecticidal protein
2011
The Vip3Aa protein is an insecticidal protein secreted by Bacillus thuringiensis during the vegetative stage of growth. The activity of this protein has been tested after different steps/protocols of purification using Spodoptera frugiperda as a control insect. The results showed that the Vip3Aa protoxin was stable and retained full toxicity after being subjected to common biochemical steps used in protein purification. Bioassays with the protoxin in S. frugiperda and S. exigua showed pronounced differences in LC(50) values when mortality was measured at 7 vs. 10d. At 7d most live larvae were arrested in their development. LC(50) values of "functional mortality" (dead larvae plus larvae rem…
Proteolytic processing of Bacillus thuringiensis Vip3A proteins by two Spodoptera species
2014
Abstract Vip3 proteins have been described to be secreted by Bacillus thuringiensis during the vegetative growth phase and to display a broad insecticidal spectrum against lepidopteran larvae. Vip3Aa protoxin has been reported to be significantly more toxic to Spodoptera frugiperda than to Spodoptera exigua and differences in the midgut processing have been proposed to be responsible. In contrast, we have found that Vip3Ae is essentially equally toxic against these two species. Proteolysis experiments were performed to study the stability of Vip3A proteins to peptidase digestion and to see whether the differences found could explain differences in toxicity against these two Spodoptera speci…
Temperature–Time Relationship in Collembolan Response to Chemical Exposure
1999
Abstract Effects of temperature on chemical toxicity to a collembolan, Folsomia candida , in relation to time were studied in this experiment. Field soil was used as a test substrate. Collembolans were incubated at three different temperatures (+13, +16, and +19°C) and in two different dimethoate concentrations (1 and 3 mg/kg), clean soil serving as the control. Four destructive samplings were done at 2-week intervals. Dimethoate degradation was also analyzed. Dimethoate 1 mg/kg had a slight effect on both adult growth and reproduction, whereas 3 mg/kg was fatal to F. candida in the soil used. Toxic effects tended to last longer at low temperature than at high temperature, but the differenc…
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…
Combining Hexanoic Acid Plant Priming with Bacillus thuringiensis Insecticidal Activity against Colorado Potato Beetle
2013
Interaction between insect herbivores and host plants can be modulated by endogenous and exogenous compounds present in the source of food and might be successfully exploited in Colorado potato beetle (CPB) pest management. Feeding tests with CPB larvae reared on three solanaceous plants (potato, eggplant and tomato) resulted in variable larval growth rates and differential susceptibility to Bacillus thuringiensis Cry3Aa toxin as a function of the host plant. An inverse correlation with toxicity was observed in Cry3Aa proteolytic patterns generated by CPB midgut brush-border membrane vesicles (BBMV) from Solanaceae-fed larvae, being the toxin most extensively proteolyzed on potato, followed…
Can herbivore-induced volatiles protect plants by increasing the herbivores’ susceptibility to natural pathogens?
2018
In response to insect herbivory, plants mobilize various defenses. Defense responses include the release of herbivore-induced plant volatiles (HIPVs) that can serve as signals to alert undamaged tissues and to attract natural enemies of the herbivores. Some HIPVs can have a direct negative impact on herbivore survival, but it is not well understood by what mechanisms. Here, we tested the hypothesis that exposure to HIPVs renders insects more susceptible to natural pathogens. Exposure of the caterpillars of the noctuid Spodoptera exigua to indole and linalool, but not exposure to (Z)-3-hexenyl acetate, increased the susceptibility to Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV). …
Broad-spectrum cross-resistance in Spodoptera exigua from selection with a marginally toxic Cry protein.
2009
BACKGROUND:Spodoptera exigua (Hubner) has developed resistance to a wide range of chemical insecticides. Products based on Bacillus thuringiensis Cry toxins are used in integrated pest management as an ecologically friendly alternative for pest control. Since there are few B. thuringiensis Cry proteins highly active against S. exigua, it is desirable to apply appropriate resistance management strategies to prevent the evolution of resistance to these proteins. RESULTS:Spodoptera exigua larvae were selected with Cry1Ab, a protein with low activity against this pest. Selected larvae developed > 30-fold resistance to Cry1Ab in 13 generations, relative to an unselected strain. The estimated rea…
Neoclerodanes from Teucrium orientale
2004
Abstract Two new neoclerodane diterpenoids, 6-deacetyl-teucrolivin A (5) and 8beta-hydroxy-teucrolivin B (6), were isolated from the aerial parts of Teucrium orientale, along with four already known neoclerodane diterpenoids, teucrolivin A (1), teucrolivin B (2), teucrolivin C (3) and teucrolivin H (4), previously isolated from Teucrium oliverianum. Their structures were elucidated on the basis of spectroscopic evidence and chemical transformations. Compounds 1-3 were assayed for antifeedant activity against Spodoptera littoralis, S. frugiperda and Heliocoverpa armigera. Teucrolivin A was the most potent of the three compounds tested.
Tadpole of Atelopus franciscus from French Guyana, with Comments on Other Larvae of the Genus (Anura: Bufonidae)
2005
The tadpole of Atelopus franciscus from French Guyana is described. It resembles other larvae of the genus, especially those displaying a color pattern of symmetrical light marks. Among them, A. franciscus is most similar to those tadpoles having submarginal papillae (i.e., Atelopus balios, Atelopus flavescens, Atelopus nanay, Atelopus tricolor). The tadpole of A. franciscus shares several similarities with the larva of A. flavescens from French Guyana but differs from it by being smaller in size and in certain measurement. The phylogenetic relevance of tadpole characters in Atelopus is discussed, including body proportions, submarginal papillae, length of upper beak.
Description of the final instar of Trichomalopsis peregrina (Hymenoptera, Pteromalidae), with data and comments on the preimaginal stages
2007
The preimaginal stages of T. peregrina are described. The egg displays a sculptured chorion, which is found only on those deposited externally. The immature larvae are characterized by their peculiarities in (a) a setose ring on the thoracic and abdominal segments, (b) an anal notch and (c) size and the sensory structures of the head capsule. The final instar is described and illustrated. Morphological structures of diagnostic value are discussed. The most salient character shown by the mature larva of this species lies in the epistoma, which is complete. Resumen. Se describen las fases de huevo y larva de T. peregrina . El huevo, como es característico en los que se depositan externamente,…