Relationship between leaf emergence and optimum spray timing for leaf blotch (Rhynchosporium secalis) control on winter barley

Abstract

For wheat, the optimum time to apply fungicide to control disease on a given leaf layer is usually at, or shortly after, full leaf emergence. Data from field experiments on barley were used to investigate whether the same relationship was applicable to control of leaf blotch on barley. Replicated plots of winter barley were sown in the autumns of 1991, 1992 and 1993 at sites in southwest England with high risk of Rhynchosporium secalis infection. Single fungicide treatments at four doses (0·25, 0·5, 0·75 or 1·0 times the label rate) were applied at one of eight different spray times, starting in midMarch in each year, with intervals of 10 -11 days between spray timings. Disease was assessed every 10-11 days and area under the disease progress curve (AUDPC) values were used to construct fungicide dose by spray time response surfaces for each of the upper four leaves, for each year. Spray timings shortly before leaf emergence were found to minimize the AUDPC for each year and leaf layer, and also the effective dose (the dose required to achieve a specified level of control), similar to wheat. Fungicide treatments on barley were effective for a longer period before leaf emergence than afterwards, probably because treatments before emergence of the target leaf reduced inoculum production on leaves below. This partly explains why fungicides tend to be applied earlier in the growth of barley compared with wheat.

Effects of disease control by fungicides on greenhouse gas emissions by UK arable crop production

“…These results are consistent with other UK published results. For example, Gladders and Hims22 and Young et al 23 found that fungicide spraying can increase winter barley yields by about 1 t ha −1 .…”

Resistance, epidemiology and sustainable management of Rhynchosporium secalis populations on barley

“…Foliar fungicides are used on most barley crops in Europe. In winter barley crops, fungicides applied in the early spring at GS25‐30 can greatly decrease disease development and therefore increase yield, but the best fungicide timing is generally at GS31‐32 (Young et al ., 2006). In spring barley crops, fungicide treatments are generally recommended where the disease is found on the upper three leaves of a susceptible cultivar.…”