Influence of Temperature, Leaf Wetness Period, Leaf Age, and Spore Concentration on Infection of Pecan Leaves by Conidia ofCladosporium caryigenum

Publisher Website
Google Scholar
Abstract
To develop a method for rapidly screening a large number of pecan seedlings in a breeding program for resistance to pecan scab, a study was conducted to determine the greenhouse environmental optima for infection by the pathogen. C. caryigenum. Optimum temperature for infection of pecan foliage ranged from 15.degree.-25.degree. C. Maximum lesion development occurred with 48 h continuous free foliar moisture. Foliar susceptibility decreased with increasing leaf age. Maximum foliar susceptibility occurred 7-21 days after bud break. Foliage became relatively resistant to infection on reaching full expansion. Lesion number and disease rating increased directly with inoculum concentration; the highest concentration, 2.5 .times. 106 conidia/ml produced the most lesions. However, lower concentrations were adequate and more practical to produce for large-scale greenhouse scab screening.