Spray additives are often used to enhance the efficacy of agrochemicals in the management of pests and diseases in vegetables but their effects can vary widely and are not fully understood This study investigated the effects of adjuvants on the retention of a systemic insecticide spray on two contrasting plant species Adjuvants provided no benefits on easytowet cucumber foliage particularly with high volume application On waterrepellent pea foliage retention of spray was enhanced by adjuvants (P

Glyphosate is used extensively for pasture renovation, with an organosilicone surfactant when treating ryegrass (Lolium perenne). The effect of a novel, non-silicone surfactant, Browndown Adjuvant, on the performance of glyphosate on perennial ryegrass was determined and compared to the organosilicone surfactant, Pulse. Spray retention, uptake and translocation of glyphosate were quantified. Comparative efficacy of spray treatments was determined in pot and field trials. Browndown increased the speed and quantity of glyphosate uptake, with no adverse effects on herbicide translocation. At the recommended rate (0.25% v/v), Browndown reduced spray retention compared to Pulse (0.1% v/v), but provided faster brown-out of foliage and equivalent herbicide efficacy on glyphosate-tolerant ryegrass in spring.

The retention of organosilicone surfactant sprays (0-0.8% v/v) on wheat was determined, using a calibrated track sprayer, over a range of spray volumes representative of ground-based arable applications (37-280 litres/ha). Volume of spray retained on foliage generally increased with carrier volume and surfactant concentration. Spray run-off was not evident with any treatment. The importance of the interaction between concentration of organosilicone and spray volume was highlighted. Spray was captured most efficiently at low spray volumes and • 0.2% surfactant. It is expected that organosilicone surfactant addition to pesticide sprays on difficult-to-wet arable species would be beneficial over a wide range of application volumes.

The interactions between the concentration of an organosilicone, Silwet L-77 ® surfactant, and spray application factors were studied. Uptake of spray solutions via stomata and the herbicidal effects of a sub-lethal rate of glyphosate generally increased with increasing Silwet L-77 concentration (0-0.4%), but the interaction between surfactant concentration and carrier volume (50-800 litres/ha) was highly significant. High surfactant concentrations induced maximal infiltration even at low spray volumes, while low concentrations provided negligible uptake via stomata, except when applied at very high spray volumes. For a constant rate of herbicide, glyphosate efficacy could be accurately predicted by total surfactant dose applied. Fine droplets (150 µm VMD) induced greater infiltration and herbicide efficacy than coarse droplets (300 µm VMD).

Three formulations of triclopyr, the ester, the amine, and amine plus organosilicone surfactant, were screened for contact phytotoxicity to the adaxial and abaxial surfaces of leaves of sweetgum, red maple and red oak, using a single concentration of herbicide and droplet size. Radiolabelled triclopyr was used to determine uptake and translocation. It was found that the amine formulation plus organosilicone surfactant, had uptake and translocation performance similar to that demonstrated with the ester formulation. Contact phytotoxicity symptoms appeared to be related to herbicide translocation.