Spatial Patterns of Fusarium Head Blight in New York Wheat Fields Suggest Role of Airborne Inoculum

Abstract

The spatial pattern of Fusarium head blight (FHB) incidence was studied in 70 winter wheat fields in New York over a period of 3 years. Incidence of FHB was randomly distributed among 60 sampling areas in 64 of the 70 fields. Fields with random FHB ranged from 0.05 to 23% in average incidence of FHB and followed bean, cabbage, corn, oat, pea, sorghum, and soybean. There was strong evidence of aggregation in FHB only in three fields that had large concentrations of corn debris. Many fields had small, scattered fragments of corn debris in evidence from a corn crop two or more years prior to wheat. The lack of aggregation in FHB and low incidences of FHB in these fields suggests that weathered corn debris contributed relatively little within-field inoculum for FHB. Based on the predominantly random patterns of FHB, disease in rotational wheat fields of New York appears to be initiated primarily by deposition of spores from diffuse atmospheric populations of G. zeae. We hypothesize that these airborne spores may originate largely from inoculum sources external to wheat fields. Over-wintered corn residue, especially from the preceding crop season, on the soil surface is the most likely potential source of regional atmospheric inoculum for FHB in New York. Accepted for publication 10 March 2003. Published 18 April 2003.