Towards Sustainable Green Adjuvants for Microbial Pesticides: Recent Progress, Upcoming Challenges, and Future Perspectives

Changes in the proteome of Apis mellifera acutely exposed to sublethal dosage of glyphosate and imidacloprid

Uncontrolled use of pesticides has caused a dramatic reduction in the number of pollinators, including bees. Studies on the effects of pesticides on bees have reported effects on both metabolic and neurological levels under chronic exposure. In this study, variations in the differential expression of head and thorax-abdomen proteins in Africanized A. mellifera bees treated acutely with sublethal doses of glyphosate and imidacloprid were studied using a proteomic approach. A total of 92 proteins were detected, 49 of which were differentially expressed compared to those in the control group (47 downregulated and 2 upregulated). Protein interaction networks with differential protein expression ratios suggested that acute exposure of A. mellifera to sublethal doses of glyphosate could cause head damage, which is mainly associated with behavior and metabolism. Simultaneously, imidacloprid can cause damage associated with metabolism as well as, neuronal damage, cellular stress, and impairment of the detoxification system. Regarding the thorax-abdomen fractions, glyphosate could lead to cytoskeleton reorganization and a reduction in defense mechanisms, whereas imidacloprid could affect the coordination and impairment of the oxidative stress response.

Multifunctional Adjuvants Affect Sulfonylureas with Synthetic Auxin Mixture in Weed and Maize Grain Yield

A field study in the years 2017-2019 was carried out to evaluate the impact of novel adjuvant formulations on the efficacy of sulfonylurea and synthetic auxin herbicides. Treatments included nicosulfuron + rimsulfuron + dicamba (N+R+D) at full and reduced rates with three multicomponent (TEST-1, TEST-2, TEST-3) as well as standard (MSO, S) adjuvants. In this greenhouse study, Echinochloa crus-galli seeds were planted and treated with N+R+D at 2-3 leaf stages. The water with the desired pH (4, 7, and 9) for the preparation of the spray liquid was prepared by incorporating citric acid or K3PO4 to either lower or raise the pH of the water. Adjuvant TEST-1 added to the spray liquid at pH 4 increased the effectiveness to 68%, TEST-2 to 81%, and TEST-3 to 80%, compared to 73% and 66% with the MSO and S. The efficacy of N+R+D at pH 7 with TEST-1 increased to 83%, TEST-2 to 82%, and TEST-3 to 77%, but with MSO, it increased to 81%, and 71% with S. Adjuvants TEST-1, TEST-2, and TEST-3 in the liquid at pH 9 increased efficacy to 76 and 80%, compared to 79 and 63% with MSO or S adjuvants. N+R+D applied with TEST-1, TEST-2, and TEST-3 provided greater weed control than herbicides with surfactant (S) and similar or even better than with standard methylated seed oil (MSO) adjuvants. Maize grain yield after herbicide-with-tested-adjuvant application was higher than from an untreated check, and comparable to yield from herbicide-with-MSO treatment, but higher than from S treatment.

Impacts of UV radiation on Bacillus biocontrol agents and their resistance mechanisms

Bacillus biocontrol agent(s) BCA(s) such as Bacillus cereus, Bacillus thuringiensis and Bacillus subtilis have been widely applied to control insects' pests of plants and pathogenic microbes, improve plant growth, and facilitate their resistance to environmental stresses. In the last decade, researchers have shown that, the application of Bacillus biocontrol agent(s) BCA(s) optimized agricultural production yield, and reduced disease risks in some crops. However, these bacteria encountered various abiotic stresses, among which ultraviolet (UV) radiation severely decrease their efficiency. Researchers have identified several strategies by which Bacillus biocontrol agents resist the negative effects of UV radiation, including transcriptional response, UV mutagenesis, biochemical and artificial means (addition of protective agents). These strategies are governed by distinct pathways, triggered by UV radiation. Herein, the impact of UV radiation on Bacillus biocontrol agent(s) BCA(s) and their mechanisms of resistance were discussed.

Exploring the efficacy of carvacrol as a biocontrol agent against pear Valsa canker

Valsa canker, a fungal disease caused by Valsa pyri, poses a significant threat to the pear industry. Currently, chemical control serves as the primary method to control valsa canker. However, the emergence of resistance can pose a challenge to its effectiveness. Biopesticides are a relatively new option for disease control, but there is limited research on their effects on pear Valsa canker. To determine the effectiveness of different biopesticides, we selected 10 common biopesticides to test their inhibition efficacy and impacts on mycelial growth rate and conidial germination. Results showed that carvacrol had very good antifungal activity; therefore its inhibition mechanisms were further investigated. Electron microscopy and transcriptome data analysis were utilized to examine how carvacrol impeded V. pyri by inducing mycelium deformation, wrinkling, and rupture. Carvacrol also affected plant hormones, thus improving plant resistance to the disease. This study lays the groundwork for the utilization of 10 distinct biopesticides to control V. pyri while elucidating how carvacrol harms the pathogen and prompts the plant defense control mechanism.