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

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These effects were apparently modified by other treatments. Thus the effect of azoxystrobin on percentagesof plants with take-all after four weeks was only apparent with the top-watering regime (P = 0.04), and aftereight weeks the apparently different effects of the two fungicides on percentages of roots with take-all weremore evident in the Woburn than in the Rothamsted soil (P = 0.02). However, because the interactions wereinconsistent (e.g. between sampling dates) and made no obvious biological sense, they are thought to bespurious.There were also significant effects of fungicide rates on percentages of roots with take-all but they weredifferent for the two fungicides (Table 9). After four weeks, azoxystrobin was apparently more effective atthe small than at the large rate whereas HGCA Z tended to increase take-all at the small but not at the largerate. For both fungicides, these effects of rate were larger with bottom than with top watering (P = 0.05).After eight weeks, azoxystrobin was again more effective at the small than at the large rate (especially withbottom watering). In contrast, HGCA Z tended to increase take-all (compared to the untreated) at the smallrate but to decrease it at the large rate (especially with top watering); the difference between the two rateswas significant.Experiment 2.3By the time that the plants in this experiment were examined for take-all, most of them were affected by thedisease (Table 10), and there was little evidence of significant differences between the treatments. The meandifferences between the fungicides and the untreated in percentages of plants with moderate or severesymptoms (and in take-all index) were not significant (Table 10) but there was strong evidence of asignificant interaction between the fungicides and the method (site) of application (i.e. soil vs foliage). Thissuggested that azoxystrobin decreased the severity of take-all only when applied to the soil whereas HGCAZ decreased take-all only when applied to the foliage. There were no significant effects of altering thetiming of fungicide applications (or of applying them twice) or of top vs bottom watering.23
Table 10. Effects of azoxystrobin and HGCA Z, applied to the soil or to the foliage, on incidence andseverity of take-all on the roots of wheat, measured at anthesis, grown in naturally-infested soil inExperiment 2.3 1 .Application toFungicide Soil Foliage Mean% plants with take-allNone +1.20(91.7) +1.20 (91.7)Azoxystrobin +1.17(91.2) +1.13 (90.5) +1.15 (90.9)HGCA Z +1.20(91.7) +1.13(90.5) +1.16(91.1)SED 2 (83DF) 120.0470.0530.0330.047Probability 3 0.69 0.69% plants with moderate or severe take-allNone -0.14 (43.3) -0.14 (43.3)Azoxystrobin -0.55 (25.1) -0.25 (37.9) -0.40 (31.2)HGCA Z + 0.03 (51.6) -0.56 (24.7) -0.26 (37.2)SED 2 (83DF) 120.2230.2500.1580.223Probability 3 0.006 0.40Take-all indexNone 47.5 47.5Azoxystrobin 42.2 45.8 44.0HGCA Z 50.8 41.7 46.3SED 2 (83DF) 123.594.022.543.59Probability 3 0.01 0.381 Data (except take-all indices) are logit transform values with, in parentheses, the corresponding percentagevalues obtained by back transformation.2 SED 1 is for comparisons between the fungicide treatments, and SED 2 for comparing any of these withnone.3 The probabilities that differences between the fungicides, excluding none, and their interactions with sites ofapplication, occurred by chance.24
Page 2 and 3: PROJECT REPORT No. 285EFFECTS OF AZ
Page 4 and 5: ABSTRACTSeverity of take-all (Gaeum
Page 6 and 7: early sprays were of azoxystrobin (
Page 8 and 9: viewed with some caution until it h
Page 10 and 11: at risk from the disease and, if co
Page 12 and 13: neither (Table 1). Dates (and growt
Page 14 and 15: dates to the foliage in plots sown
Page 16 and 17: Table 3. Effects of azoxystrobin an
Page 18 and 19: Table 5. Effects of azoxystrobin an
Page 20 and 21: significant effect. Results from th
Page 22 and 23: Total numbers of plants and roots (
Page 24 and 25: Table 8. Effects of fungicides, app
Page 28 and 29: DISCUSSIONThe results from the fiel
Page 30 and 31: effects that strobilurin fungicides
Page 32 and 33: Table 12 (Experiment 1 of Jenkyn et
Page 34 and 35: REFERENCESBateman, G.L. (1989). Pro

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

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