First report of target-site resistance to ACCase-inhibiting herbicides in Bromus tectorum L.

BACKGROUND: The prevalent and repeated use of acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides for Bromus tectorum L. control in fine fescue (Festuca L. spp) grown for seed has selected ACCase-resistant B. tectorum populations. The objectives of this study were to (1) evaluate the response of nine B. tectorum populations to the ACCase inhibitors clethodim, sethoxydim, fluazifop-P-butyl, and quizalofop-P-ethyl and the acetolactate synthase (ALS) inhibitor sulfosulfuron and (2) characterize the resistance mechanisms. RESULTS: Bromus tectorum populations were confirmed to be resistant to the ACCase-inhibiting herbicides tested. The levels of resistance varied among the populations for clethodim (resistance ratio, RR = 5.1-14.5), sethoxydim (RR = 18.7-44.7), fluazifop-P-butyl (RR = 3.1-40.3), and quizalofop-P-ethyl (RR = 14.5-36). Molecular investigations revealed that the mutations Ile2041Thr and Gly2096Ala were the molecular basis of resistance to the ACCase-inhibiting herbicides. The Gly2096Ala mutation resulted in cross-resistance to the aryloxyphenoxypropionate (APP) herbicides fluazifop-P-butyl and quizalofop-P-ethyl, and the cyclohexanedione (CHD) herbicides clethodim, and sethoxydim, whereas Ile2041Thr mutation resulted in resistance only to the two APP herbicides. All B. tectorum populations were susceptible to sulfosulfuron (RR = 0.3-1.7). CONCLUSIONS: This is the first report of target-site mutations conferring resistance to ACCase-inhibiting herbicides in B. tectorum. The results of this study suggest multiple evolutionary origins of resistance and contribute to understanding the patterns of cross-resistance to ACCase inhibitors associated with different mutations in B. tectorum. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mobility and environmental monitoring of pesticides in the atmosphere - a review.

Knowledge of the partition mechanisms in the agrochemical environment is fundamental for understanding their behavior within an ecosystem and mitigating possible adverse effects of these products. In this review, the objective was to present the main transport mechanisms, physical-chemical properties, and atmospheric monitoring methodologies of the most diverse types of agrochemicals used in agriculture that can reach the atmosphere and affect different compartments. It has been verified that volatilization is one of more considerable significance of the various forms of transport since a significant part of the applied pesticides can volatilize in a few days. As for monitoring these compounds in the atmosphere, both passive and active sampling have their advantages and disadvantages. Passive samplers allow sampling in large quantities and at remote locations, in addition to making continuous measurements, while active samplers have the advantage of being able to detect low concentrations and continuously. Since a significant portion of the applied pesticides is directed to the atmosphere, monitoring makes it possible to understand some properties of the pesticides present in the air. This monitoring can be done from different existing methodologies based on adopted criteria and existing technical standards. Graphical representation of mobility and environmental monitoring of atmospheric pollutants from pesticides.

Morphoanatomical injuries in Pistia stratiotes L. (Araceae) as a result of exposure to clomazone in water.

Contamination of water sources due to herbicide is of great concern. Clomazone is a pesticide with a high contamination potential which could possibility lixiviate to water streams. Changes caused by residual herbicide include flora modifications which are generally detrimental for some species. The lack of morphological studies performed in aquatic plants exposed to herbicide-contaminated environments has encouraged the development of our research. For the first time, we present a study that aimed to evaluate leaf injuries visible to the naked eye as well as microscopical effects which may be caused by clomazone on Pistia stratiotes. Pistia stratiotes was subjected to five concentrations of clomazone. Our analysis showed leaf injuries, especially after 15 days of clomazone application. Hormesis was observed when the water lettuce was subjected to the lower concentrations. Total leaf area showed increase following by reduction while injured until reaching the highest concentration. Although the concentrations of clomazone tested in our study are not lethal to water lettuce, such herbicide have still caused morphoanatomical damages on leaves which advocates for the use of P. stratiotes as a bioindicator of the presence of herbicides such as clomazone in water.

Sensitivity of the macrophytes Pistia stratiotes and Eichhornia crassipes to hexazinone and dissipation of this pesticide in aquatic ecosystems.

Herbicide wastes from agriculture areas can contaminate water resources and affect non-target organisms. Since herbicides reach groundwater and rivers, these residues can damage the aquatic ecosystem. Hexazinone is an herbicide widely used in sugarcane cultivation and has a potential to contaminate water resources. Therefore, studies are necessary to know the possible damages of this herbicide on aquatic organisms, as well as the behavior of this pesticide in those systems. In this study, our objective was to evaluate the sensitivity of the macrophytes Pistia stratiotes and Eichhornia crassipes to hexazinone, as well as the dissipation of these pesticides. The variables intoxication, fresh matter accumulation, and leaf anatomy were used to evaluate the sensitivity of the macrophytes to hexazinone. The hexazinone concentration in water was performed by HPLC-MS. Hexazinone concentrations equivalent to 111 and 333 µg L-1 were toxic to the macrophytes. Pistia stratiotes produced less fresh matter production than Eichhornia crassipes when exposed to the hexazinone. The hexazinone application did not change the adaxial epidermic (EAD), abaxial epidermic (EAB), palisade parenchyma (PP), aerenchyma (AER) and leaf blade (LAF) of Pistia stratiotes at any concentration tested. Concentrations equivalent to 333 µg L-1 changed the PP and LAF of Eichhornia crassipes. The presence of this herbicide in water negatively affects the fresh matter accumulation and leaf structure of the Pistia stratiotes and Eichhornia crassipes, respectively. The presence of these macrophytes delayed the dissipation of hexazinone due to them impair other pathways of degradation of this herbicide in aquatic environments. The presence of this herbicide in water negatively affects the growth and development of the Pistia stratiotes and Eichhornia crassipes.

Pathogenicity of Metarhizium anisopliae and Beauveria bassiana fungi to Tetranychus ludeni (Acari: Tetranychidae) / Patogenicidade de fungos Metarhizium anisopliae e Beauveria bassiana ao Tetranychus ludeni (Acari: Tetranychidae)

The use of acaricides is the main control method for Tetranychus ludeni (Acari: Tetranychidae) in horticultural crops. This mite has been recorded causing damage to sweet potato (Ipomoea batatas L.). The use of pathogenic fungi is an alternative to chemical control. The objective was to evaluate the pathogenicity of the fungi Metarhizium anisopliae (Meetch) Sorok, and Beauveria bassiana (Bals.) Vuill. to phytophagous mite T. ludeni in sweet potato plants. Conidial suspensions of M. anisopliae and B. bassiana, at concentrations of 106 and 107 con.mL-1 were applied to sweet potato leaves. After 24 hours, five females of T. ludeni newly emerged were released on the leaves. The bioassay was arranged in a completely randomized design with factorial arrangement 2 × 2 (two species of fungi and two concentrations) plus the control (distilled water), with 10 repetitions per treatment. The evaluation consisted of observing of three biological parameters of the mite: mortality, oviposition, and repellency, after 24, 48, 72, and 96 hours of contact with the fungi. The isolates of M. anisopliae cause high mortality rates of T. ludeni in laboratory. Beauveria bassiana has the potential to suppress future generations of mite, reducing its oviposition rate. Repellency behavior was not observed.(AU)

O uso de acaricidas é o principal método de controle de Tetranychus ludeni (Acari: Tetranychidae) em cultivos hortícolas. Esse ácaro foi registrado causando danos em batata-doce (Ipomoea batatas (L.). A utilização de fungos patogênicos é uma alternativa ao controle químico. O objetivo foi avaliar a patogenicidade dos fungos Metarhizium anisopliae (Meetch) Sorok. e Beauveria bassiana (Bals.) Vuill. ao ácaro fitófago T. ludeni em batata-doce. Suspensões conidiais de M. anisopliae e B. bassiana, nas concentrações de 106 e 107 con.mL-1, foram aplicadas sobre folhas de batata-doce. Após 24 horas, cinco fêmeas recém-emergidas foram liberadas sobre as folhas. O bioensaio foi inteiramente randomizado, com arranjo fatorial 2 × 2 (duas espécies de fungos e duas concentrações) e controle (água destilada), com 10 replicações por tratamento. A avaliação consistiu na observação de três parâmetros biológicos do ácaro: mortalidade, oviposição e repelência, após 24, 48, 72 e 96 horas de contato com os fungos. Os isolados de M. anisopliae causam altas taxas de mortalidade de T. ludeni em laboratório. Beauveria bassiana tem potencial para suprimir futuras gerações do ácaro, reduzindo a taxa de oviposição. Comportamento de repelência nos ácaros não foi observado.(AU)

Phytoremediation of Brazilian tree species in soils contaminated by herbicides.

The phytoremediation potential of Brazilian trees species Calophyllum brasiliense, Eremanthus crotonoides, Hymenaea courbaril, Inga striata, and Protium heptaphyllum was investigated for contaminated soils containing ametryn and hexazinone. Visual injury, chlorophyll content, plant height, leaf temperature, leaf number, and water-efficient use were evaluated. Residual herbicides at soil substrates were analyzed by LC/MS. Among the species C. brasiliense and H. courbaril were tolerant to both herbicides. P. Heptaphyllum presented tolerance at ametryn treatment. E. crotonoides, I. striata, and P. heptaphyllum died in hexazinone treatment. A high content of residual ametryn was found for E. crotonoides. In ametryn treatment, residual herbicide has decreased for C. brasiliense and E. crotonoides species. C. brasiliense highlighted among others becoming a good agent for phytoremediation of soils contaminated with traces of ametryn and hexazinone.