Efeito de Bacillus thuringiensis Berliner e inseticidas químicos sobre a traça-das-crucíferas, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) e seus parasitóides

Monnerat *, § , Luke Masson R., Brousseau R., Pusztai-Carey M., Bordat D., Frutos R.

Whole-crystal preparations from strains HD-1 and HD-133, activated Cry1Ab and Cry1C toxins as well as Cry1Aa, Cry1Ac, Cry1D, and Cry2Aa protoxins were tested for toxicity to 2nd-instar larvae of the diamondback moth, Plutella xylostella. Mortality data recorded after 2 and 5 days provided different results that were related to differential rates of solubilization, activation, and degradation of insecticidal crystal proteins. The two most active proteins are Cry1Ab and Cry1C, which are both present in HD-133. The Cry1Ab protoxin is activated within 2 days, whereas activation of the Cry1C protoxin occurs between 2 and 5 days. HD-133 is more active than HD-1 immediately after infection and remains toxic over 5 days owing to the sequential activation of its crystal components. Solubility properties of crystals and rates of activation of protoxins influence the overall toxicity of HD-1 and HD-133 to the diamondback moth.

Monnerat R.G., Bordat D.

Laboratory experiments have shown that HD1 strain of #Bacillus thuringiensis# Berliner has adverse effects on #Diadegma# sp. Young larvae of #Plutella xylostella# (L.), the diamondback moth (DBM), were killed by #B. thuringiensis# when the larvae were parasitized by #Diadegma# for only a short time (less than two days). Larvae were parasitized for more than two days before adding the bacterium, however, they decreased their foliar consumption (35% less) and therefore consumed fewer spores of #B.thuringiensis#. The low mortality of the DBM allows the parasitoid to finish its development. The presence of HD1 does not affect the F1 generation of #Diadegma# sp. There are no significant differences in the time of the larval stage and pupal development, sex-ratio, longevity of adults and percentage of parasitism between adults from HD1 infected or non-infected larvae

Freire Í.A., Nascimento I.N., Rocha G.T., Santos P.D., Cunha B.B., Ferreira A.D., Moreira F.M., Castro M.T., Monnerat R.G.

The biological control of pests and diseases in Brazilian crops has increased substantially, and the large-scale multiplication of microorganisms, a practice known as “On Farm”, is now being used by farmers. In this study, we aimed to produce and evaluate the quality of Bacillus thuringiensis var. kurstaki strain HD-1 in “On Farm” biofactories under three aeration rates (0.2, 0.5 and 0.8 air volume/volume of medium/min) (vvm), with regard to the production of endospores and crystals, contaminants, and to calculate the lethal concentration 50 (LC50) against Spodoptera frugiperda larvae. After 48 h, the number of viable spores differed significantly between 0.2 (5.75 × 107), 0.5 (1.33 × 108) and 0.8 (5.40 × 108) vvm. The culture media did not show enough selectivity. A significant difference was observed for the LC50 calculated for 0.2 vvm (7.06 × 104), 0.5 vvm (2.07 × 104), 0.8 vvm (4.40 × 103), and the commercial product (3.79 × 103). The results of this study showed that the aeration rate affects the multiplication efficiency of B. thuringiensis in biofactories. In addition, post-process quality control analyses found no pathogenic contamination, reinforcing the safety and viability of the production process. The 0.8 vvm rate resulted in the greater production of spores and crystals, and statistically similar results to the commercial product for the control of S. frugiperda.

Lima B.S., Rocha F.A., Plata-Rueda A., Zanuncio J.C., Cossolin J.F., Martínez L.C., Serrão J.E.

Anticarsia gemmatalis is a defoliator caterpillar of soybean that can be controlled by chemical and biological agents. However, resistant populations of this insect have been reported, which requires research to identify control alternatives. Abamectin acts by contact and ingestion, affecting the muscles and nervous system of insects. However, its effect on other organs has not been evaluated. The present study aimed to evaluate the side effects of oral exposure to abamectin in A. gemmatalis caterpillars. Abamectin is lethal to A. gemmatalis with LC50/72 h = 96 (74–125) mg a.i. L−1. The survival of caterpillars exposed to different lethal concentrations of this insecticide decreases from 99.9% untreated, to 65.1%, 42.6%, 16.8%, and 0% with the LC25/72 h, LC50/72 h, LC75/72 h, and LC90/72 h, respectively. Abamectin reduced leaf consumption by A. gemmatalis, indicating an anti-feeding effect. In addition, the insecticide damaged the midgut cells of A. gemmatalis, and caused the degeneration of the peritrophic matrix, disorganization of epithelial striated border, accumulation of mitochondria with different shapes, increased autophagy and release of cell fragments into the midgut lumen. The goblet cells also underwent striated border disorganization in insects exposed to abamectin. The results indicate that abamectin reduces survival and digestive processes of A. gemmatalis after oral exposure and may be an important tool for controlling this pest.

de Carvalho Silva A., de Araújo C.R., Vázquez L.L.

Numerous insects inhabit the vegetables crops and their control is necessary. The biological control plays an important role in the management of phytophagous insects these environment using natural enemies in the augmentative (ABC) or conservative biological control (CBC). This chapter provides data on the status of ABC in Latina America and also reports plants that can be used in crop diversification to CBC of the main pests of vegetables. We reviewed studies regarding the main predators, parasitoids, and entomopathogens of phytophagous insects limiting for the production of vegetables in Latin-American countries.

Telles C.C., Freitas L.M., Junqueira A.M., Mendonça R.S.

ABSTRACT Integrated pest management (IPM) strategies are among the factors promoting plant resistance to pests, and silicon application may increase this resistance. Thus, the aim of this research was to evaluate the control of diamondback moth (DBM), Plutella xylostella (Lepidoptera, Plutellidae) through foliar application of silicon in cabbage crops. The experiment was conducted in the vegetable producing area of Água Limpa Farm, Universidade de Brasília, Distrito Federal, Brasil. The experimental design was of randomized blocks with nine treatments and four replicates, totaling 36 plots. The applied treatments consisted of Agrosilicon® (10.5% Si) (T1), Sifol® (12% Si) (T2), deltamethrin 25 g L-1 (Decis® 25 EC) (T3), Bacillus thuringiensis, 33.60 g L-1 (Dipel® SC) (T4), Agrosilicon® + deltamethrin 25 g L-1(Decis® 25 EC) (T5), Agrosilicon® + Bacillus thuringiensis, 33.60 g L-1 (Dipel® SC) (T6), Sifol® + deltamethrin 25 g L-1 (Decis® 25 EC) (T7), Sifol® + Bacillus thuringiensis, 33.60 g L-1 (Dipel® SC) (T8) and control (T9). Agrosilicon® and Sifol® were applied weekly and the products deltamethrin and Bacillus thuringiensis were applied according to the damage level established for DBM in cabbage crops. Foliar application of silicon, alone or in combination with chemical and biological insecticides - T2, T7 and T8, were the best strategy to control DBM in cabbage crops, resulting in the lowest number of caterpillars per plant, lowest leaf damages and best aesthetic value of plants. Silicon foliar application can be considered as an auxiliary method of DBM management in cabbage crops, followed by the doses recommended by the manufacturers.

Xia Y., Xu J., Duan J., Liu Q., Huang H., Yi Z., Chen Z.

Miscanthus lutarioriparius, a domestic species of China, belongs to the genus of perennial rhizomatous Miscanthus and is a promising energy crop for biomass production. To establish an Agrobacterium tumefaciens transformation protocol and obtain transgenic plants co-expressing the Cry 2Aa#and Bar genes, an Agrobacterium-mediated transformation method for M. lutarioriparius was developed in this study. To inhibit tissue browning, optimized callus induction and regeneration media were developed. Embryogenic calli were efficiently induced from immature inflorescences on Murashige & Skoog (MS) medium containing 0.2 g L−1citric acid. Agrobacterium tumefaciens EHA105 carrying pC3300 with the Cry 2Aa#and Bar genes were introduced into embryogenic calli. Six transgenic lines were selected by Basta screening and confirmed by genomic PCR. The herbicide tolerance of M. lutarioriparius transgenic plants was verified by spraying with glufosinate and expression of the Cry 2Aa#protein by ELISA. Therefore, an Agrobacterium-mediated transformation protocol for M. lutarioriparius was established and the co-expression of herbicide tolerance and Cry 2Aa#was successfully introduced with the system.

Pereira J., Monteiro L.B., Gómez D.R.

ABSTRACT Bioinsecticides based on Bacillus thuringiensis are the entomopathogen most marketed worldwide. The aim of this study was to evaluate the bioactivity of kurstaki, aizawai subspecies and kurstaki x aizawai hybrid on B. salubricola larvae fed on artificial diet in different assessment periods. Mortality was assessed on the seventh, tenth and fifteenth days after treatment. Microplates containing 150 µl of diet in each cell were used. Suspensions containing Bt subspecies was deposited on the surface of the diet, then neonate larvae were released. The mortality assessment performed after fifteen days of treatment was significant for all three subspecies. Bt kurstaki was more efficient in all assessment periods, except for fifteen days, which was similar to Bt aizawai. Assessments performed up to seven days were more efficient to determine mortality. The three subspecies have influenced the ability for instar change, regardless of concentration. The LC50 of Bt kurstaki on the seventh and tenth days of assessment was from three to six times smaller than that observed in Bt aizawai x kurstaki, and Bt aizawai, respectively.

Mezzomo B.P., Miranda-Vilela A.L., de Souza Freire I., Barbosa L.C., Portilho F.A., Lacava Z.G., Grisolia C.K.

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Moraes C.P., Foerster L.A.

Plutella xylostella L. is the most important worldwide pest of cruciferous plants and indiscriminate use of insecticides has led to the resistance of the species to different groups. This research was conducted to compare the toxicity and persistence of two strains of Bacillus thuringiensis to P. xylostella larvae. Concentrations between 125 and 500g 100L-1 of water of the commercial products were evaluated and compared to the insect growth inhibitor diflubenzuron and to the neurotoxic pyrethroid deltamethrin. The efficacy of the insecticides was compared between treated plants kept indoor greenhouse and outdoor. Third instar larvae were more susceptible to B. thuringiensis than first instar ones. Agree and Dipel showed similar control rates of third instars until 10 days after treatment, but on the 15th day, Agree was significantly more efficient than Dipel. Both B. thuringiensis formulations showed a reduction in mortality after 10 days when the treated plants were exposed to natural weather conditions in comparison to the same treatments kept inside greenhouse. Dimilin (100g 100L-1 of water) and deltamethrin (30ml of commercial product 100L-1 of water) were not efficient to control third instar larvae of P. xylostella. This inefficiency cannot be attributed to a resistant population of P. xylostella since the larval population used in the experiments was not subjected to insecticide pressure, once the crop was organically cultivated all year round. The results showed that both formulations of B. thuringiensis are sound alternatives for the control of the diamondback moth in organically conducted cruciferous crops, considering the high residual control provided under subtropical weather conditions.

Martinelli S., Montagna M.A., Picinato N.C., Silva F.M., Fernandes O.A.

A eficiência do indoxacarb foi avaliada no controle dos lepidópteros-pragas em hortaliças: Plutella xylostella (Lepidoptera: Yponeumatidae), Trichoplusia ni (Lepidoptera: Noctuidae), Neoleucinodes elegantalis (Lepidoptera: Pyralidae) e Helicoverpa zea (Lepidoptera: Noctuidae). Os experimentos foram conduzidos em três locais diferentes nas culturas do repolho e tomate. Os inseticidas utilizados foram indoxacarb (no tomate de 2,4 a 6,0 g i.a./100 L e no repolho de 18 a 42 g i.a./ha), esfenvalerate (apenas no tomate de 1,75 g i.a./100 L), metomil (no tomate na dose de 21,5 g i.a./100 L e no repolho a 172 g i.a./ha), deltametrina (apenas no repolho na dose de 6 g i.a./ha) e triflumuron (apenas no tomate na dose de 15 g i.a./100 L). Adotou-se o delineamento estatístico em blocos ao acaso com quatro repetições em todos os experimentos. Todas as doses avaliadas do produto indoxacarb apresentaram excelente desempenho no controle de P. xylostella e T. ni. Assim, a menor dose avaliada (18 g i.a./ha) pode ser recomendada para o controle dessas pragas. Todos os produtos avaliados alcançaram níveis de eficiência maiores que 80% no controle de H. zea na cultura do tomate. Indoxacarb foi tão eficiente quanto o produto padrão adotado (triflumuron). N. elegantalis foi eficientemente controlada pelos inseticidas avaliados após nove aplicações, sendo que indoxacarb pode ser recomendado na menor dose utilizada (2,4 g i.a./100 L).