Survival Rates of Tobacco Budworm (Lepidoptera: Noctuidae) Larvae Exposed to Transgenic Cottons Expressing Insecticidal Protein of Bacillus thuringiensis Berliner

2000 ◽  
Vol 35 (2) ◽  
pp. 105-117 ◽  
Author(s):  
C. D. Parker ◽  
V. J. Mascarenhas ◽  
R. G. Luttrell ◽  
K. Knighten
Keyword(s):  
Bacillus Thuringiensis ◽  
Insecticidal Activity ◽  
Heliothis Virescens ◽  
Survival Rates ◽  
Larval Survival ◽  
Tobacco Budworm ◽  
Bt Cotton ◽  
Plant Structure ◽  
Lepidoptera Noctuidae ◽  
Insecticidal Plants

The insecticidal activity of transgenic cottons expressing endotoxin protein of Bacillus thuringiensis Berliner (Bt cotton) was quantified by measuring survival of tobacco budworm, Heliothis virescens (F.), larvae caged on different plant structures for varying lengths of exposure. Percentages of larvae surviving were measured on Bt cottons expressing Cry1Ab and CrylAc protein. Plant structure (terminal, leaf, square or boll) did not affect larval survival, and survival did not differ significantly between CrylAb and CrylAc cottons. Larvae exposed to Bt cotton for only 24 h had higher initial survival than larvae exposed for 48, 72 and 96 h. Larvae first exposed to Bt cotton at 4 d of age had higher survival than those first exposed as neonate or 2-d-old larvae. Survivorship of neonate and 4-d-old larvae exposed to CrylAc cotton was significantly reduced with only 48 h of exposure to the insecticidal plants. Seven-day-old larvae exhibited no significant reduction in survivorship with exposure to CrylAc cotton for 48 h.

Microplitis croceipes (Hymenoptera: Braconidae) Development in Tobacco Budworm (Lepidoptera: Noctuidae) Larvae Treated with Bacillus thuringiensis and Thiodicarb

1999 ◽  
Vol 34 (2) ◽  
pp. 249-259 ◽  
Author(s):  
D. W. Atwood ◽  
T. J. Kring ◽  
S. Y. Young
Keyword(s):  
Bacillus Thuringiensis ◽  
High Mortality ◽  
Heliothis Virescens ◽  
Laboratory Tests ◽  
Resistance Management ◽  
Tobacco Budworm ◽  
Microplitis Croceipes ◽  
Host Mortality ◽  
Lepidoptera Noctuidae

Bacillus thuringiensis Berliner var. kurstaki and thiodicarb were evaluated in laboratory and field assays to determine the effect on tobacco budworm larvae, Heliothis virescens (F.), and the parasitoid Microplitis croceipes Cresson. Laboratory trials were conducted using B. thuringiensis concentrations of 0, 10, 50 and 250 ppm and thiodicarb concentrations of 0, 12.5, 25, 50, 100, and 200 ppm in the diet. The test using field-treated cotton squares was conducted using B. thuringiensis and thiodicarb, independently and in combination, at rates recommended for resistance management in Arkansas. Laboratory tests indicated that tobacco budworm mortality was directly related to B. thuringiensis and thiodicarb concentrations, although B. thuringiensis only significantly increased tobacco budworm mortality at the highest concentration of exposure in the absence of parasitization. Parasitization increased host mortality at all B. thuringiensis experimental rates after 6 and 14 days. Although host mortality increased linearly with increasing thiodicarb concentration, parasitization did not significantly increase host mortality over thiodicarb alone until day 14. Emergence of M. croceipes was inversely related to B. thuringiensis and thiodicarb concentration. In assays using squares from field-sprayed cotton, thiodicarb and thiodicarb/B thuringiensis mixtures provided significantly greater tobacco budworm mortality than did B. thuringiensis application alone. In addition, no significant advantage was determined for tank mixtures with B. thuringiensis as compared to thiodicarb application alone. However, neither B. thuringiensis nor thiodicarb, alone or in combination, caused a high mortality of early third instar tobacco budworm in the absence of parasitization by M. croceipes.

Mortality of Tobacco Budworm Larvae (Lepidoptera: Noctuidae) and Emergence of Cotesia marginiventris (Hymenoptera: Braconidae) Exposed to Bacillus thuringiensis and Thiodicarb Alone and in Combination

1998 ◽  
Vol 33 (2) ◽  
pp. 136-141 ◽  
Author(s):  
D. W. Atwood ◽  
S. Y. Young ◽  
T. J. Kring
Keyword(s):  
Bacillus Thuringiensis ◽  
Heliothis Virescens ◽  
Detrimental Effect ◽  
Larval Mortality ◽  
Resistance Management ◽  
Tobacco Budworm ◽  
Cotesia Marginiventris ◽  
Larval Parasitoid ◽  
Parasitoid Population ◽  
Lepidoptera Noctuidae

Mortality of Heliothis virescens (F.) larvae and emergence of Cotesia marginiventris (Cresson) were evaluated on terminals collected from cotton in fields treated with Bacillus thuringiensis Berliner var. kurstaki and thiodicarb. Tests were conducted using B. thuringiensis and thiodicarb, independently and in combination. Insecticide rates were those recommended for resistance management in Arkansas. Results indicate that neither B. thuringiensis nor thiodicarb, alone or in combination, provided acceptable control of H. virescens larvae (<33%) by day 16. However, thiodicarb and thiodicarb/B. thuringiensis mixtures provided significantly greater control of H. virescens than did B. thuringiensis application alone. In addition, no significant advantage was gained with tank mixtures of B. thuringiensis and thiodicarb as compared to thiodicarb application alone. Parasitization increased early larval mortality (day 2) only in conjunction with the application of B. thuringiensis. Neither insecticide applied independently nor in combination had a significant impact on the emergence of C. marginiventris from H. virescens. Overall, while results indicated unsatisfactory control of H. virescens, findings indicated no detrimental effect on the larval parasitoid population at rates suggested for resistance management.

Tobacco Budworm, Heliothis virescens (Lepidoptera: Noctuidae): Larval Location and Mortality on Bacillus thuringiensis-Treated Cotton

1999 ◽  
Vol 34 (4) ◽  
pp. 426-434 ◽  
Author(s):  
J. L. Jyoti ◽  
S. Y. Young ◽  
D. T. Johnson ◽  
R. W. McNew
Keyword(s):  
Bacillus Thuringiensis ◽  
Leaf Area ◽  
Food Consumption ◽  
Heliothis Virescens ◽  
Untreated Control ◽  
Larval Mortality ◽  
Tobacco Budworm ◽  
Lepidoptera Noctuidae ◽  
Larval Movement

One-d-old Heliothis virescens (F.) larvae were placed on Bacillus thuringiensis var. kurstaki Berliner-treated cotton leaves and terminals in the laboratory. Larval movement, food consumption and mortality were examined at 3, 6, 12, 24 and 48 h. Untreated leaves had a greater percentage of larvae on their under side than on their upper side; this location was not influenced by treatment with B. thuringiensis. When B. thuringiensis was applied to cotton terminals, first instars moved from B. thuringiensis-treated meristems; this movement increased with an increase in rate. Bacillus thuringiensis treatment also resulted in increased movement of larvae from the leaves and terminals onto the inner cup surface, although this movement was significantly greater than the untreated control only during the first 12 h after treatment. The leaf area consumed decreased with an increase in B. thuringiensis rate, but was not significantly correlated with larval mortality.

scholarly journals Ecdysteroidogenesis in Heliothis virescens (Lepidoptera: Noctuidae): Recombinant Prothoracicotropic Hormone and Brain Extract Show Comparable Effects

2019 ◽  
Vol 19 (3) ◽  
Author(s):  
Marisa Nardiello ◽  
Rosanna Salvia ◽  
Andrea Scala ◽  
Carmen Scieuzo ◽  
Sabino Aurelio Bufo ◽  
...  
Keyword(s):  
Heliothis Virescens ◽  
Complex Mixture ◽  
Prothoracic Gland ◽  
Tobacco Budworm ◽  
Brain Extract ◽  
In Vitro Tests ◽  
Prothoracicotropic Hormone ◽  
Lepidoptera Noctuidae

Abstract Prothoracicotropic hormone (PTTH) is a neuropeptide that triggers a cascade of events within the prothoracic gland (PG) cells, leading to the activation of all the crucial enzymes involved in ecdysone biosynthesis, the main insect steroid hormone. Studies concerning ecdysteroidogenesis predicted PTTH action using brain extract (BE), consisting in a complex mixture in which some components positively or negatively interfere with PTTH-stimulated ecdysteroidogenesis. Consequently, the integration of these opposing factors in steroidogenic tissues leads to a complex secretory pattern. A recombinant form of prothoracicotropic hormone (rPTTH) from the tobacco budworm Heliothis virescens (F.) (Lepidoptera: Noctuidae) was expressed and purified to perform in vitro tests in a standard and repeatable manner. A characterization of rPTTH primary and secondary structures was performed. The ability of rPTTH and H. virescens BE to stimulate ecdysteroidogenesis was investigated on the third day of fifth larval stage. rPTTH activity was compared with the BE mixture by enzyme immunoassay and western blot, revealing that they equally stimulate the production of significant amount of ecdysone, through a transduction cascade that includes the TOR pathway, by the phosphorylation of 4E binding protein (4E-BP) and S6 kinase (S6K), the main targets of TOR protein. The results of these experiments suggest the importance of obtaining a functional pure hormone to perform further studies, not depending on the crude brain extract, composed by different elements and susceptible to different uncontrollable variables.

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