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Canopy Temperature as a Correlative Measure for Assessing Host Response to Septoria tritici Blotch of Wheat. Z. Eyal, Department of Botany, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel. A. Blum, Department of Field Crops, The Volcani Center, ARO, Bet-Dagan 50250, Israel. Plant Dis. 73:468-471. Accepted for publication 8 December 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0468.

The relationships between canopy temperature measured by an infrared thermometer and the response to Septoria tritici blotch of 43, 31, and 33 cultivars of bread, durum, and triticale, respectively, were evaluated during 3 years in the field. Measurements of canopy temperatures at midday and the percent of pycnidia coverage were taken in Septoria-infected plots and in fungicide-protected plots on several dates after anthesis. Canopy temperatures increased with the increase in disease coverage and with the decrease in green leaf area. When canopy temperatures were recorded before maturity, and when cultivars varied in disease coverage, the correlations between the two variables ranged from r = 0.48 (P = 0.01) to r = 0.74 (P = 0.01), depending on year and date. The association between canopy temperature and disease coverage generally improved when evaluated within cultivars of similar phenology and maturity. Canopy temperatures were positively correlated with the area under the Septoria progress curve and with losses in kernel weight. Infrared thermometry of Septoria-infected wheat canopies can be used as a measure for estimating differences in cultivarsí response to Septoria tritici blotch.