Effect of additives in aqueous formulation on the foliar uptake of dimethomorph by cucumbers

Suspension Concentrate crop protection formulation design and performance for low spray volume and UAS spray application

BACKGROUND

Unmanned aerial systems (UAS) are providing interesting disruptive solutions for spray application of crop protection products with very-low spray volumes (VLV) down to 8 L/ha that offer improved sustainability through reduced water volumes and reduced soil compaction. However, the efficacy of products can be reduced by the significantly lower crop/plant spray coverage and formulation designs that can compensate for this are highly important here.

RESULTS

Suspension Concentrate (SC) formulations designed for VLV use containing and delivering low dose rates (g/ha) of organosilicone alkoxylate high-spreading surfactants were found to result in leaf coverage of VLVs comparable to those observed at higher spray volumes. High spreading was observed on textured leaf surfaces containing sub-micron sized epicuticular wax crystals. Greenhouse fungal disease studies showed enhanced efficacy with these SC formulations compared to standard SC formulations without these additives and maintained the observed increase in efficacy when applied at VLV. Alternatively, SC formulations without high spreading formulants but containing uptake promoting nonionic surfactants showed enhanced cuticle penetration through isolated cuticles at VLV in comparison to higher spray volumes, with coffee-ring spray deposit microstructures present at VLVs. Similarly, greenhouse studies showed enhanced efficacy that was maintained at VLV relative to SCs without these additives.

CONCLUSION

At VLVs, SC formulations applied at relatively low dose rates (g/ha) of formulants (adjuvants) enhancing spreading on the leaf surface and/or uptake of the active ingredient(s) maintained good spreading, uptake and biological efficacy in greenhouse studies overcoming the coverage limitations of SC formulations without these additives. This result is unexpected considering the low dose rate of adjuvants used. © 2023 Bayer AG. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Volatilisation of pesticides under field conditions: inverse modelling and pesticide fate models

BACKGROUND

A substantial fraction of the applied crop protection products on crops is lost to the atmosphere. Models describing the prediction of volatility and potential fate of these substances in the environment have become an important tool in the pesticide authorisation procedure at the EU level. The main topic of this research is to assess the rate and extent of volatilisation of ten pesticides after application on field crops.

RESULTS

For eight of the ten pesticides, the volatilisation rates modelled with PEARL (Pesticide Emission Assessment at Regional and Local scales) corresponded well to the calculated rates modelled with ADMS (Atmospheric Dispersion Modelling System). For the other pesticides, large differences were found between the models. Formulation might affect the volatilisation potential of pesticides. Increased leaf wetness increased the volatilisation of propyzamide and trifloxystrobin at the end of the field trial. The reliability of pesticide input parameters, in particular the vapour pressure, is discussed.

CONCLUSION

Volatilisation of propyzamide, pyrimethanil, chlorothalonil, diflufenican, tolylfluanid, cyprodinil and E- and Z-dimethomorph from crops under realistic environmental conditions can be modelled with the PEARL model, as corroborated against field observations. Suggested improvements to the volatilisation component in PEARL should include formulation attributes and leaf wetness at the time of pesticide application. © 2015 Society of Chemical Industry.

The contribution of spray formulation component variables to foliar uptake of agrichemicals

BACKGROUND

The objective of the present study was to determine the contribution of the active ingredient (AI) and surfactant, and their concentrations, to the foliar uptake of agrichemicals, and to examine the physical properties that would need to be included in a model for foliar uptake.

RESULTS

All spray formulation component variables significantly affected uptake, explaining 73% of the deviance. The deviance explained by each factor ranged from 43% (AI concentration nested within AI) to 5.6% (surfactant). The only significant interaction was between AI and surfactant, explaining 15.8% of the deviance. Overall, 90% of the deviance could be explained by the variables and their first-order interactions.

CONCLUSIONS

Uptake increased with increasing lipophilicity of the AI at concentrations below those causing precipitation on the leaf surface. AI concentration had a far greater (negative) effect on the uptake of the lipophilic molecule epoxiconazole. The uptake of 2-deoxy-D-glucose (DOG) and 2,4-dichlorophenoxyacetic acid (2,4-D) increased with increasing hydrophile-lipophile balance (HLB) of the surfactant, the effect of HLB being far greater on the hydrophilic molecule DOG. However, the differences observed in epoxiconazole uptake owing to the surfactant were strongly positively related to the spread area of the formulation on the leaf surface. For all AIs, uptake increased in a similar manner with increasing molar surfactant concentration.

The formulation makes the honey bee poison

Dr. Fumio Matsumura's legacy embraced a passion for exploring environmental impacts of agrochemicals on non-target species such as bees. Why most formulations are more toxic to bees than respective active ingredients and how pesticides interact to cause pollinator decline cannot be answered without understanding the prevailing environmental chemical background to which bees are exposed. Modern pesticide formulations and seed treatments, particularly when multiple active ingredients are blended, require proprietary adjuvants and inert ingredients to achieve high efficacy for targeted pests. Although we have found over 130 different pesticides and metabolites in beehive samples, no individual pesticide or amount correlates with recent bee declines. Recently we have shown that honey bees are sensitive to organosilicone surfactants, nonylphenol polyethoxylates and the solvent N-methyl-2-pyrrolidone (NMP), widespread co-formulants used in agrochemicals and frequent pollutants within the beehive. Effects include learning impairment for adult bees and chronic toxicity in larval feeding bioassays. Multi-billion pounds of formulation ingredients like NMP are used and released into US environments. These synthetic organic chemicals are generally recognized as safe, have no mandated tolerances, and residues remain largely unmonitored. In contrast to finding about 70% of the pesticide active ingredients searched for in our pesticide analysis of beehive samples, we have found 100% of the other formulation ingredients targeted for analysis. These 'inerts' overwhelm the chemical burden from active pesticide, drug and personal care ingredients with which they are formulated. Honey bees serve as an optimal terrestrial bioindicator to determine if 'the formulation and not just the dose makes the poison'.

Penetrative and dislodgeable residue characteristics of 14C-insecticides in apple fruit

Infinite- and finite-dose laboratory experiments were used to study the penetrative and dislodgeable residue characteristics of (14)C-insecticides in apple fruit. The differences in dislodgeable and penetrated residues of three radiolabeled insecticides ((14)C-thiamethoxam, (14)C-thiacloprid, and (14)C-indoxacarb), applied in aqueous solution with commercial formulations, were determined after water and methanol wash extractions. The rate of sorption and extent of penetration into the fruit cuticles and hypanthium of two apple cultivars were measured after 1, 6, and 24 h of treatment exposure, using radioactivity quantification methods. For all three compounds, 97% or more of the treatment solutions were found on the fruit surface as some form of non-sorbed residues. For indoxacarb, sorption into the epicuticle was rapid but desorption into the fruit hypanthium was delayed, indicative of a lipophilic penetration pathway. For the neonicotinoids, initial cuticular penetration was slower but with no such delay in desorption into the hypanthium.