New Pyrethroids for Use Against Tuta Absoluta (Lepidoptera: Gelechiidae): Their Toxicity and Control Speed.

Insect pests are responsible for major losses in crop productivity, and insecticides are the main tools used to control these organisms. There is increasing demand for new products for pest management. Therefore, the aim of this study was to assess the toxicity of pyrethroids with acid moiety modifications to measure the insecticidal activity of these compounds on Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). First, we synthesized E/Z mixtures of five pyrethroids: [9], [10], [11], [12], and [13]. Then, we separated the cis and trans pyrethroid isomers of [9], [10], [11], and [12]. We assessed the toxicity of these compounds against T. absoluta. The E/Z mixtures of the five pyrethroids (30 µg of substance per mg-1 of insect) caused high (100%) and rapid (<12 h) tomato borer mortality. The cis isomer of pyrethroid [10] was the most toxic to T. absoluta, causing mortality similar to permethrin. The other isomers were less powerful than permethrin.

Detailed search for protein kinase(s) involved in plasma membrane H+-ATPase activity regulation of yeast cells.

This study displays a screening using yeast strains deficient in protein kinases known to exist in Saccharomyces cerevisiae. From 95 viable single mutants, 20 mutants appear to be affected in the glucose-induced extracellular acidification. The mutants that are unaffected in calcium signaling were tested for their sensitivity to hygromycin B. Furthermore, we verified whether the remaining mutants produced enzymes that are appropriately incorporated at plasma membrane. Finally, we measure the kinetic properties of the enzyme in purified plasma membranes from glucose-starved as well as glucose-fermenting cells. We confirmed the kinase Ptk2 involvement in H(+)-ATPase regulation (increase of affinity for ATP). However, the identification of the kinase(s) responsible for phosphorylation that leads to an increase in Vmax appears to be more complex. Complementary experiments were performed to check how those protein kinases could be related to the control of the plasma membrane H(+)-ATPase and/or the potential membrane. In summary, our results did not permit us to identify the protein kinase(s) involved in regulating the catalytic efficiency of the plasma membrane H(+)-ATPase. Therefore, our results indicate that the current regulatory model based on the phosphorylation of two different sites located in the C-terminus tail of the enzyme could be inappropriate.

Performance of cotton expressing Cry1Ac, Cry1F and Vip3Aa19 insecticidal proteins against Helicoverpa armigera, H. zea and their hybrid progeny, and evidence of reduced susceptibility of a field population of H. zea to Cry1 and Vip3Aa in Brazil.

The genetically modified cotton DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 expressing Cry1Ac, Cry1F and Vip3Aa19 from Bacillus thuringiensis Berliner (Bt) has been cultivated in Brazil since the 2020/2021 season. Here, we assessed the performance of DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton expressing Cry1Ac, Cry1F and Vip3Aa19 against Helicoverpa armigera (Hübner), Helicoverpa zea (Boddie), and their hybrid progeny. We also carried out evaluations with DAS-21023-5 × DAS-24236-5 cotton containing Cry1Ac and Cry1F. In leaf-disk bioassays, DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 was effective in controlling neonates from laboratory colonies of H. armigera, H. zea and the hybrid progeny (71.9%-100% mortality). On floral bud bioassays using L2 larvae, H. zea presented complete mortality, whereas H. armigera and the hybrid progeny showed <55% mortality. On DAS-21023-5 × DAS-24236-5 cotton, the mortality of H. armigera on leaf-disk and floral buds ranged from 60% to 73%, whereas mortality of hybrids was <46%. This Bt cotton caused complete mortality of H. zea larvae from a laboratory colony in the early growth stages, but mortalities were <55% on advanced growth stages and on floral buds. In field studies conducted from 2014 to 2019, DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton was also effective at protecting plants against H. armigera. In contrast, a population of H. zea collected in western Bahia in 2021/2022 on Bt cotton expressing Cry1 and Vip3Aa proteins, showed 63% mortality after 30 d, with insects developing into fifth and sixth instars, on DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton. We conclude that H. armigera, H. zea, and their hybrid progeny can be managed with DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton; however we found the first evidence in Brazil of a significant reduction in the susceptibility to DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 cotton of a population of H. zea collected from Bt cotton in Bahia in 2021/2022.

Spatial-temporal distribution of Dalbulus maidis (Hemiptera: Cicadellidae) and factors affecting its abundance in Brazil corn.

BACKGROUND: Since the last decade, Dalbulus maidis has become the primary pest in cornfields, particularly due to its ability to transmit plant pathogens. Dalbulus maidis is the main vector of the corn stunt spiroplasma and maize bushy stunt phytoplasma. However, there is little information available on this pest. Understanding its spatial dynamics may allow us to determine how its infestations begin and to identify its colonization patterns, dispersal, and the role of landscape structure on D. maidis dynamics. Thus, this study aimed to investigate within-field spatial distribution and the factors associated with D. maidis abundance in five commercial fields. RESULTS: In all fields, higher infestations occurred at the boundaries of the central pivot, showing a clear edge-biased distribution. Ranges varied from 100.4 to 611.8 m, and our models' overall fit indicated strong to moderate spatial dependency. Additionally, correlation analyses indicated a positive effect of air temperature on the population of D. maidis. Conversely, rainfall negatively affected D. maidis. CONCLUSION: This study provides essential guidance for improving D. maidis integrated pest management at regional and local scales. Based on its high dispersal ability, our study suggests the need for a legislative or regulatory method of control for D. maidis, especially in regions where corn has more than one growing season. © 2022 Society of Chemical Industry.

Investigation of the lethal and behavioral effects of commercial insecticides on the parasitoid wasp Copidosoma truncatellum.

Copidosoma truncatellum (Hymenoptera: Encyrtidae) is an important parasitoid wasp of the soybean looper, Chrysodeixis includens, but its effectiveness can be severely curtailed by the application of certain insecticides. Therefore, to identify insecticides that are potentially compatible with C. truncatellum, the lethal and behavioral effects of nine chemicals used to control the soybean looper were evaluated for their toxicity to the wasp. Chlorantraniliprole, chlorfenapyr, flubendiamide, and indoxacarb were the least toxic insecticides to the parasitoid, resulting in mortalities of less than 25%. In contrast, cartap, deltamethrin, and methomyl caused 100% mortality, and acephate and spinosad caused 76% and 78% mortality, respectively. At least one of the detoxifying enzymes (monooxygenase, glutathione S-transferase, and/or esterases) may be involved in the mechanisms underlying the selectivity of chlorantraniliprole, chlorfenapyr, flubendiamide, and indoxacarb for the parasitoid based on the results for the insecticide plus synergist treatment. Changes in the behavioral patterns (walking time and resting time) of the parasitoid were found with exposure to acephate, flubendiamide, indoxacarb and methomyl, but behavioral avoidance was not observed. Our results indicate that the insecticides chlorantraniliprole and chlorfenapyr are the most suitable for inclusion in integrated pest management strategies for the control of C. includens.

Comparação genotípica de isolados de Corynebacterium pseudotuberculosis de caprinos e ovinos do sertão de Pernambuco / Genotypic comparison between Corynebacterium pseudotuberculosis samples obtained from sheep and goats with caseous lymphadenitis, raised in the semi-arid region of Pernambuco

Objetivou-se com este estudo comparar genotipicamente 35 isolados de Corynebacterium pseudotuberculosis recuperados de conteúdo de abscessos de caprinos e ovinos com linfadenite caseosa, procedentes de cinco municípios localizados no Sertão de Pernambuco, Brasil. Utilizou-se a técnica de fingerprint RFLP-PCR com as enzimas de restrição Hpy-Ch4 e Msp1 aplicada ao gene rpoB e as enzimas Pst I e Msp I para o gene pld. Não houve diferença nos padrões de fragmentos de bandas entre os isolados, independente da espécie hospedeira ou da área geográfica estudada, definindo-se um padrão genotípico homogêneo de C. pseudotuberculosis responsável por abscessos superficiais na região.(AU)

The objective was to genotypically compare 35 samples of Corynebacterium pseudotuberculosis obtained from abscesses of sheep and goats diagnosed with caseous lymphadenitis originated from 5 different municipalities in the semi-arid region of Pernambuco, Brazil. The RFLP-PCR technique with Hpy-Ch4 and Msp I and Pst I Msp I restriction enzimes was used to fingerprint the genes rpoB and pld, respectively. The results demonstrate that there was no difference on the fragments banding pattern among samples, independently of the host species or geographic area studied, defining a homogeneous profile of C. pseudotuberculosis responsible for superficial abscesses for the region.(AU)