Effect of adjuvants on the performance of the new cereal fungicide, metconazole. II Field trials

Abstract Glasshouse trials had shown that the activity of metconazole formulations against cereal foliar diseases could be enhanced by alcohol ethoxylate adjuvants. A series of soluble liquid (SL) formulations of metconazole had been prepared containing adjuvant: metconazole ratios of 5:1, 7.5:1, 10:1, 15:1 m/m (SL1, SL2, SL3, SL4) which glasshouse trials had shown could give equivalent performance to an emulsifiable concentrate formulation, (ECM) of metconazole at application rates up to three‐ or four‐fold lower than that of ECM alone. A field trials programme was undertaken to compare the performances of these SL formulations with ECM at 120 g AI ha −1 , through a range of application rates (48, 60, 72, 84 g AI ha −1 ), in a non‐orthogonal factorial trial design against diseases that occurred naturally ( Septoria tritici Rob., Puccinia recondita Rob., Pyrenophora teres Drechs., Erysiphe graminis DC) or by artificial inoculation ( Leptosphaeria nodorum Muell.), on either Triticum aestivum L. or Hordeum vulgare L. The results from trials in three locations showed that the commercially acceptable performance of ECM at 120 g AI ha −1 , in giving high levels of control of P. recondita, S. tritici and L. nodorum (both prophylactic and therapeutic activity) on T. aestivum. and of E. graminis and P. teres on H. vulgare , could be matched or improved by SL2, SL3 and SL4 at 72 g AI ha −1 . Furthermore, control of E. graminis f. sp. tritici Marchal by these SL formulations at this application rate was better than that by ECM at 120 g AI ha −1 , though the levels of control still remained below commercial acceptability for therapeutic activity. Nevertheless, substantial reductions in the application rate of metconazole have been achieved by using one‐pack adjuvant‐containing formulations in field trials, while still maintaining excellent control of a range of cereal foliar diseases. The choice between these SL formulations could therefore be made on other grounds such as cost/performance and ease of formulation.