Nine percent of trees in a sycamore progeny test on a Mississippi River delta site [USA] exhibited leaf scorch, dieback and lethal cankers [caused by fungi] by age 4 yr. This represented an increase from 5% affected trees in May to 9% affected in Sept. of the 4th growing season. Southern seed sources were least susceptible. Disease symptoms were negligible in similar tests at 3 locations outside of the delta. Six-month-old seedlings representing some progeny families in the field tests were inoculated with Botryodiplodia theobromae in a greenhouse. Significant genetic variation among families within sources but not among sources was obtained for disease development. Correlations between greenhouse and field results were positive but low.