EFFECT OF THE VOLUME RATE OF APPLICATION ON THE GLASSHOUSE PERFORMANCE OF CROP PROTECTION AGENT ADJUVANT COMBINATIONS

The effects of volume rate of application on the glasshouse performanc e of three recently developed crop protection agent/adjuvant combinati ons are discussed. High volume rates of application on easy-to-wet fol iage, such as potato (Solanum tuberosum, L.) caused reduction of the a djuvant-enhanced performance of dimethomorph seen at low volume rates. These reductions were largely attributable to relatively lower spray retention with spray drop coalescence and run-off being observed, part icularly at the higher adjuvant rates. On difficult-to-wet foliage (wh eat, Triticum aestivum, L.; oat, Avena saliva, L.) two different effec ts were seen. With a metconazole formulation/'Dobanol' 91-6 combinatio n on wheat, no systematic changes in performance were observed with ch ange in volume rate. With a flamprop-M-isopropyl formulation/'Dobanol' 25-7 combination, statistically significant increases in performance were seen with increasing volume rate. In both cases the observations can be explained as the result of a combination of interacting factors involving spray pattern, spray deposition and, by inference, foliar u ptake of the crop protection agent, the proportions of which differed between the two cases. It is suggested that the effect of volume rate of application on performance of adjuvant-containing formulations is i nvestigated on easy-to-wet foliage to determine the upper limits and o n difficult-to-wet foliage to determine any variation in performance t hat may occur. Such information will guide the design of field trials and may aid interpretation of field results.