Owlet moths (Lepidoptera: Noctuoidea) associated with Bt and non- Bt soybean in the brazilian savanna / Noctuóides (Lepidoptera: Noctuoidea) associados a soja Bt e não-Bt no Cerrado brasileiro

Abstract The use of GMO expressing Bt toxin in soybean production has increased significantly in the last years in Brazil in order to manage the damage caused by lepidopteran pests. In this study, we compared the richness and abundance of owlet moths (Noctuoidea) associated with Bt and non-Bt soybean. We determined the temporal variations as a function of phenology, and correlated the population variations of the most common species with meteorological variables. The research was conducted at the experimental area of Embrapa Cerrados. The collection method used was differentiated being suppressive and absolute. A total of 13 species were collected, of which eight occurred on Bt soybeans. The most representative taxa were Chrysodeixis includens (72.87%), Anticarsia gemmatalis (18.17%) and Spodoptera spp (5.22%). The number of larvae belonging to species targeted by the Bt technology was 10 times lower on Bt than on non-Bt soybeans. Utetheisa ornatrix and Elaphria deltoides were recorded on soybean for the first time, observing larvae of both species in non-Bt soybean and those of U. ornatrix also in Bt soybean. Only A. gemmatalis larvae correlated (p <0.05) negatively with precipitation. This study provided field information on the abundance and species richness of owlet moths on non-Bt soybeans, associated with the effects of Bt soybean. When considering the different levels of infestation between cultivars as a criterion, larvae monitoring is of substantial importance in order to develop the lost control program.

Resumo O uso de OGM que expressam toxina Bt na produção de soja tem aumentado significativamente nos últimos anos no Brasil e são utilizados para conter os danos causados ​​pelos lepidópteros pragas. Neste estudo comparamos a riqueza e a abundância de Noctuoides (Noctuoidea) associados à soja Bt e não-Bt. Determinamos as variações temporais em função da fenologia e correlacionamos às variações populacionais das espécies mais comuns com variáveis ​​meteorológicas. A pesquisa foi conduzida na área experimental da Embrapa Cerrados. O método de coleta utilizado foi diferenciado sendo supressivo e absoluto. Um total de 13 espécies foram coletadas, das quais oito ocorreram em soja Bt. Os taxa mais representativos foram Chrysodeixis includens, Anticarsia gemmatalis e Spodoptera spp. O número de larvas pertencentes às espécies alvo da tecnologia Bt foram 10 vezes menores na soja Bt do que em soja não-Bt . Utetheisa ornatrix e Elaphria deltoides foram registradas na soja pela primeira vez, observando-se larvas de ambas espécies na soja não-Bt e as de U. ornatrix também na soja Bt. Somente as larvas de A. gemmatalis se correlacionaram (p <0,05) negativamente com a precipitação. Este estudo forneceu informações em campo sobre a abundância e riqueza de espécies na soja não- Bt, associada aos efeitos da soja Bt. A importância do monitoramento das lagartas é substancial, a fim de tomar a melhor decisão de controle, considerando-se os diferentes níveis de infestação entre cultivares como critério.

Characterization of Cry toxins from autochthonous Bacillus thuringiensis isolates from Mexico / Caracterización de toxinas Cry de aislados de Bacillus thuringiensis autóctonos de México

Abstract: Background: Chemical pesticides, widely used in agriculture and vector-borne disease control, have shown toxic effects on the environment and the people in contact with them. Bacillus thuringiensis is a widely used bacterium for alternative and safer control of insect pests. Its toxins are specific for insects but innocuous for mammals and may be used as powerful adjuvants when applied with vaccines. The objective of this work was to characterize some autochthonous B. thuringiensis strains, which could be used for the control of a local pest (Diatraea considerata Heinrich) that affects sugar cane crops in Sinaloa, Mexico. Also, to evaluate these strains as a source of Cry toxins, which may be used in the future as adjuvants for some vaccines. Methods: Eight strains from field-collected dead insects were isolated. These were microbiologically identified as B. thuringiensis and confirmed by amplification and sequencing of 16S rDNA. Bioassays were performed to evaluate their pathogenicity against D. considerata, and Cry toxins were identified by proteomic analyses. Results: An increased mortality among larvae infected with strain Bt-D was observed, and its toxin was identified as Cry1Ac. Conclusions: The observed data showed that the selected strain was pathogenic to D. considerata and seemed to produce Cry1Ac protein, which has been reported as an adjuvant in different types of immunization.

Resumen: Introducción: Los pesticidas químicos, ampliamente usados en agricultura y en el control de vectores transmisores de enfermedades, han mostrado efectos tóxicos sobre el medio ambiente y las personas expuestas a ellos. Bacillus thuringiensis es una bacteria ampliamente utilizada como una alternativa segura y eficaz en el control biológico de plagas agrícolas. Sus toxinas son específicas de insectos, pero inocuas para mamíferos, e incluso poseen gran potencial para ser usadas como adyuvantes en vacunas. El objetivo de este trabajo fue caracterizar cepas autóctonas de B. thuringiensis con efectividad contra el gusano barrenador (Diatraea considerata Heinrich) de la caña de azúcar en cultivos del estado de Sinaloa, México, y como fuente de proteínas Cry, con potencial de utilizarse como adyuvantes en vacunas. Métodos: Se lograron aislar ocho cepas a partir de insectos muertos en campos agrícolas, las cuales fueron identificadas microbiológicamente como B. thuringiensis, lo que se confirmó por amplificación y secuenciación del 16S rDNA. La efectividad de los aislados para el control del gusano barrenador fue evaluada mediante bioensayos y las toxinas Cry fueron identificadas por análisis proteómico. Resultados: Se observó una mortalidad elevada en las larvas infectadas con las cepas de estudio. Particularmente, la cepa Bt-D, de la cual el análisis molecular mostró que posee una toxina tipo Cry1Ac. Conclusiones: Los resultados mostraron que la cepa Bt-D posee un elevado potencial patogénico hacia D. considerata y produce la proteína Cry1Ac, de la cual existen reportes de su aplicación como adyuvante en diferentes formas de inmunización.

Expression of cry1Ab gene from a novel Bacillus thuringiensis strain SY49-1 active on pest insects

ABSTRACT In this study, the cry1Ab gene of previously characterized and Lepidoptera-, Diptera-, and Coleoptera-active Bacillus thuringiensis SY49-1 strain was cloned, expressed and individually tested on Ephestia kuehniella (Lepidoptera: Pyralidae) and Plodia interpunctella (Lepidoptera: Pyralidae) larvae. pET-cry1Ab plasmids were constructed by ligating the cry1Ab into pET28a (+) expression vector. Constructed plasmids were transferred to an Escherichia coli BL21 (DE3) strain rendered competent with CaCl2. Isopropyl β-D-1-thiogalactopyranoside was used to induce the expression of cry1Ab in E. coli BL21(DE3), and consequently, ∼130 kDa of Cry1Ab was obtained. Bioassay results indicated that recombinant Cry1Ab at a dose of 1000 µg g-1 caused 40% and 64% mortality on P. interpunctella and E. kuehniella larvae, respectively. However, the mortality rates of Bt SY49-1 strains' spore-crystal mixture at the same dose were observed to be 70% on P. interpunctella and 90% on E. kuehniella larvae. The results indicated that cry1Ab may be considered as a good candidate in transgenic crop production and as an alternative biocontrol agent in controlling stored product moths.

Electroantennogram responses of the potato tuber moth, Phthorimaea operculella (Lepidoptera; Gelichiidae)to plant volatiles.

Electroantennograms (EAGs)were recorded from males and females of the potato tuber moth,Phthorimaea operculella in response to a broad range of plant volatile compounds belonging to diverse chemical classes.The responses to 27 compounds were evaluated,which indicated significant differences in EAGs between chemicals as well as between sexes.The fatty acid derivatives comprising essentially green leaf volatile components elicited significantly greater responses in females.The response profile of males was,in general,lower than that of females.EAG responses to the oxygenated and hydrocarbon monoterpenes were lower in both males and females.Dose -response studies indicate differences in response between the sexes and concentrations,suggesting the existence of sexual dimorphism. Compounds belonging to the fatty acid derivatives class appear to be important for an oligophagous pest such as the potato tuber moth and the findings are discussed in relation to host plant selection in this species.

Development and mechanisms of resistance to Bacillus thuringiensis endotoxin Cry1Ac in the American bollworm, Helicoverpa armigera (Hübner).

The American bollworm, H. armigera, evolved 31-fold resistance to selection pressure of B. thuringiensis endotoxin Cry1Ac within six generations. The Cry1Ac selected larvae of H. armigera showed cross-resistance to Cry1Aa and Cry1Ab both in terms of mortality and growth reduction. Studies on mechanisms of resistance to Cry1Ac showed that proteases of resistant insects degraded Cry1Ac faster than those of susceptible insects, which led to the relative unavailability of toxin of about 58 kDa for binding and perforation of midgut epithelial membrane of the target insect. Besides, resistant and susceptible populations of H. armigera differed in the binding of their receptors with Cry1Ac toxin. These results suggest the possibility of both mechanisms existing in imparting resistance. These findings mandate the necessity of B. thuringiensis resistance management for usage of B. thuringiensis either as a conventional insecticide or through transgenic crops.

Potentiation of insecticidal activity of Bacillus thuringiensis subsp. kurstaki HD-1 by proteinase inhibitors in the American bollworm, Helicoverpa armigera (Hübner).

The effect of crude proteinase inhibitor extracts from seeds of different crop plants (black gram, chickpea, chickling vetch, finger millet, French bean, green gram, horse gram, lentil, pea and soybean) on the insecticidal activity of B. thuringiensis var. kurstaki HD-1 was investigated against neonate larvae of H. armigera by diet incorporation method. The larval mortality due to crude proteinase inhibitors alone (5% seed weight equivalent) ranged from 4.1 to 19.1%; the maximum mortality with finger millet and the minimum with pea var. DDR-23. A mixture of B. thuringiensis var. kurstaki HD-1 (10 ppm) and proteinase inhibitor (5% seed weight equivalent) was synergistic in larval mortality with respect to proteinase inhibitors of pea var. DMR-16, chickling vetch var. RLK-1098 and B101-212, lentil var. ILL-8095 and L-4076, soybean var. PK-1042, PK-416 and Pusa-22, chickpea var. Pusa-413, French bean (Chitra) and black gram; and antagonistic with respect to those of finger millet, horse gram and kidney bean. The larval growth reduction with crude proteinase inhibitors alone ranged from 17.9 to 53.1%; the maximum growth reduction with soybean var. PK-1042 and minimum with lentil var. L-4076. A mixture of B. thuringiensis var. kurstaki and proteinase inhibitor was synergistic in growth reduction with respect to proteinase inhibitors of lentil var. ILL-8095, and L-4626 and antagonistic with respect to that of finger millet. The midgut proteinase inhibition with crude seed extracts (3.3% seed weight equivalent) ranged from 9.3 to 60.9% and was negatively correlated with larval mortality. These results showed that interactive effect of B. thuringiensis var. kurstaki HD-1 and proteinase inhibitors in the larvae of H. armigera depended upon the quality and quantity of proteinase inhibitors, which vary widely in different plants.

Modified behaviour in nucleopolyhedro virus infected field bean pod borer, Adisura atkinsoni and its impact on assessing the field efficacy of NPV.

When nucleopolyhedro virus of A. atkinsoni was applied at 250 LE/ha, there was no significant difference between the viruses treated and control plots with regard to the total number of live larvae feeding outside the pod. However, due to changes in behaviour in NPV infected A. atkinsoni by way of coming out of the pod, there was a significant difference when counts were taken with regard to total number of larvae found feeding inside the pod. Both endosulfan at (0.07%) and virus (125 LE/ha) in combination with endosulfan (0.035%) significantly reduced the larval population of A. atkinsoni and Sphaenarches anisodactylus. There was no significant difference between the virus and control plots with regard to percentage of pod damage. However, when the yield was assessed based on the seed weight, there was significant difference.

DNA synthesis in the imaginal wing discs of the American bollworm Helicoverpa armigera (Hübner).

The effect of two insect growth regulators of plant origin viz. plumbagin and azadirachtin and the ecdysteroids 20-hydroxyecdysone, makisterone A and a phytoecdysteroid on DNA synthesis in imaginal wing discs of day 4 final instar Helicoverpa armigera larvae was studied. DNA synthesis increased with increase in time of incubation up to 8 h and decreased later without the addition of moulting hormone. Addition of 20-hydroxyecdysone supported long term acquisition of competence for DNA synthesis in the wing discs. Both DNA synthesis and protein content were drastically reduced in plumbagin and azadirachtin-treated insects. Under in vitro conditions, plumbagin had a more pronounced inhibitory effect than azadirachtin. All the ecdysteroids tested, viz. makisterone A, 20-hydroxyecdysone and the ecdysteroidal fraction from the silver fern Cheilanthes farinosa enhanced DNA synthesis.

Morphogenetic derangements in the reproductive system of Bracon hebetor, a beneficial parasitoid, bred on juvenoid treated host (Corcyra cephalonica) larvae.

Effect of juvenoids (hydroprene and methoprene) on the ecto-parasite B. hebetor was investigated by rearing them upon the juvenoid treated ultimate instar host larvae of C. cephalonica. Emerged adultoid wasps of either sexes obtained from treated series showed anatomical deformities in the reproductive systems. Ill-developed ovaries with reduced length, terminally free ovarioles and abnormal testicular growth showing non-fusion of lobes were the important abnormal features. Data on measurements of male reproductive system, e.g., width (transverse axis) of testis, length of common vas deferens plus ejaculatory duct and length of accessory gland showed significant difference (P < 0.05) from control.

Effect of fumigation and juvenile hormone on oxygen consumption of the larvae of Corcyra cephalonica (Stainton).

Reduced effect of JH-I, JH-II and JH-III on oxygen consumption of II-V instars and increased effect on the oxygen consumption of VI instar larvae suggested that control of corcyra with juvenile hormones could be brought about only when applied to just emerged VI instar larvae. Similarly fumigation of juvenile hormone treated larvae could prove beneficial only at VI instar stage. The possibility of enhancing the effect of fumigant with pretreatment of JH will be futile as even only JH treated VI instar larvae develop into abnormal individuals which die later.

Growth inhibitory and antifeedant activity of extracts from Melia dubia to Spodoptera litura and Helicoverpa armigera larvae.

The growth inhibitory activity and deterrency of Melia dubia (Meliaceae) extracts to Spodoptera litura and Helicoverpa armigera were investigated. Artificial diet bioassays using neonate larvae of both S. litura and H. armigera indicated that dichloroethane (DCE) and methanol (Me) extracts of M. dubia inhibited growth in a dose dependent manner. DCE and Me-5II fractions also resulted in 50% deterrency at concentrations of 22.5 and 16.8 micrograms/cm2 respectively against S. litura larvae in a leaf disc-choice test. The DCE-5 fraction was found to be more toxic to larvae (LC50 of 0.65%) than the Me-5II (LC50 of 0.8%), 72 hr after topical application. Both fractions lack contact toxicity, but the deterrent effect persisted for at least 60 hr under laboratory conditions. Although salannin was isolated from the DCE fraction to show antifeedant activity, the physico-chemical characteristics of the active fractions DCE-5 and Me-5II were not identical with either salannin or azadirachtin.

Toxicity of insecticides to the cotton leaf worm moth. an electrophysiological [ETS] study

The present work, ETS records were carried out from the tarsal sesillum chaticum of the cotton leaf worm moth fore leg. The aim was to compare between the toxicity of carbamate, organophosphates [OPS], and pyrethroids insecticides of different concentrations. All records showed a concentration-dependent responses for all used insecticides. The toxic effects of carbamate and OPs appeared as hyperactivity followed by an excitation for several minutes and then convulsion and paralysis. This is believed to result from their inhibitory effects on the A cetylcholinesterase [AChE] and the ACh - receptor complex [AChR] which results in accumulation of the ACh at the cholinergic synapse inducing hyperpolarization, and thereby triggering repetitive action potentials of high amplitude followed by hyperexcitation which ultimately lead to death. The toxic effects of pyrethroids appeared as an increased depolarization and multiple nervous discharges which believed to result from their interference wit ion transport processes in the nervous tissue to the inhibition of the inactivation mechanism of Na* channels .The ETS records may be helpful in testing and comparing between the effects of these types of insecticides on the cotton, leaf worm moth by a method for from fields to estimate the minimum effective dose used. This leads to restoring the use of insecticides when necessary and decreasing the pollution of the environment

Comparative toxicity of trivalent and hexavalent chromium compounds in fig moth Ephestia cautella (Walker).

Of the trivalent (CrSO4) and hexavalent (K2Cr2O7) chromium compounds, only the hexavalent produced significant deleterious effects on development and fertility of E. cautella, when eggs were reared on laboratory medium supplemented with different concentrations of these salts.