Decision support system to control Puccinia hordei on barley based on disease threshold values and weather criteria (United Kingdom 1992 to 1993)
1994
Schoefl, U. | Zinkernagel, V. | Verreet, J.A. (Technische Univ. Muenchen, Freising-Weihenstephan (Germany). Lehrstuhl fuer Phytopathologie)
A series of field trials was carried out in Suffolk, England, during 1992 and 1993 to evaluate an integrated disease control model for barley. In each year high levels of barley leaf rust established on the upper leaf layers of the winter barley cultivar 'Marinka' whereas other pathogens were present only at low levels that had little or no effects on yield. Although a high proportion of plants was already infected at early growth stages (GS 30 onwards) strong disease development did not occur before GS 71/75. This was mainly due to dependence of Puccinia hordei on high temperatures combined with frequent rainfall. The calculated regression equation between weekly mean temperature and disease progress showed exponential character (R-Square = 81 percent) therefore much development of Puccinia hordei below weekly mean temperatures of 15 degrees is very unlikely. Using this, with a disease threshold value of more than 30 per cent of infected fillers, it is possible to estimate the need for a fungicide application and then to determine the optimal application timing for most effective control of the fungus. A range of single sprays as well as two and three spray programmes were used to test these decision criteria. Within the trials, yield losses of up to 18 per cent were caused by brown rust and single applications of tebuconazole (Folicur) at GS 45/49 were very effective against this disease, yielding the same as two and three spray programmes at half or full rates of use. The decision criteria enable an effective application timing under variable climatic conditions and have been integrated into a decision support system to control diseases on winter and spring barley.
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