PROJECT REPORT No. 285 EFFECTS OF ... - HGCA

the foliage but this result must be treated with caution especially as the fungicide had no effect when appliedto the soil in the same experiment. In Experiment 2.2 there were a number of significant interactionsinvolving watering regimes but the apparent effects of top vs bottom watering were inconsistent andprobably spurious. Different effects of large vs small rates of application for the two fungicides inExperiment 2.2 were, however, more consistent being very similar for plants sampled after 4 weeks or after 8weeks. These results, which indicated that azoxystrobin was more effective at the smaller than at the largerof the two rates tested (possibly indicating slight phytotoxicity at the larger rate) were not disimilar to theeffects of azoxystrobin in Experiment 2.1. In the latter experiment, HGCA Z was, in contrast, more effectivein decreasing take-all at the larger than at the smaller rate. The average effects of HGCA Z in Experiment2.2 were small and not significant but after 8 weeks it, similarly, seemed to decrease the severity of take-allat the large rate but not at the small. Further work is, therefore, needed to confirm the effects on take-all ofHGCA Z. By comparison with azoxystrobin this may help to explain the behaviour and effects of both.ACKNOWLEDGEMENTSWe thank the companies that provided the fungicides that were tested in this project, Zeneca (now part ofSyngenta) for permission to take samples from their experiments, A.D. Todd for statistical analyses and R.H.Bromilow for helpful discussions. IACR receives grant-aided support from the Biotechnology andBiological Sciences Research Council of the United Kingdom.30