ADJUVANTS FOR USE WITH FOLIAR FUNGICIDES

Adjuvants for use with fungicides have been known since the first stud ies on formulation efficiency and it is now well known that the activi ty of systemic fungicides can be improved by a proper choice of additi ves and/or adjuvants. Several studies have clearly demonstrated that t hese improvements result from changes in such factors as droplet forma tion, surface contact and behaviour of the deposit, penetration into t he leaf (transcuticular or stomatal) and transport within the plant, a s well as interactions within the fungal cell. The transfer of these r esults from laboratory studies to field trials often yields inconsiste nt results and simulation models often fail to predict the behaviour o f adjuvants under field conditions. This is probably because many fact ors are involved which cannot be controlled in the field. For example, droplet formation can be very different, leaf structure and canopy fo rmation can interfere, and results for one particular fungicide/crop/f ungus/adjuvant combination cannot be translated to another situation. This multiplicity of very complex interactions is probably the main re ason why there has been no general breakthrough in practical adjuvant use with fungicides. More applied research is needed to optimise the s pecific application conditions for each crop/fungicide/fungus combinat ion. There are still some unresolved problems associated with the use of adjuvants such as loss of selectivity and the occurrence of phytoto xic side-effects. Also some unexpected specific interactions between a djuvants and formulation constituents can influence the activity which necessitate more fundamental studies on the biochemical and physicoch emical background of their mode of action.