Disease Cycle
The Phialophora gregata fungus is a deuteromycete with a monocyclic life cycle. There are two strains of Phialophora gregata, referred to as genotype A and genotype B. Genotype A causes both foliar and stem symptoms, while genotype B causes only stem symptoms.
The Phialophora gregata fungus produces no survival structures, but can overwinter as mycelium in decaying soybean residue. During overwintering, conidia are produced; these conidia are the inoculum for new plants in the spring. The amount of asexual reproduction that occurs during the winter affects the spring inoculum levels. Infection initially occurs in the roots of young soybean plants, and then spreads to the stem (and foliage, depending on the strain). Generally, early and severe foliar symptoms indicate that the yield losses will be heavier.
Read more about this topic: Phialophora Gregata
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