The red color may show only near the dead tip of the root or it may extend the length of the root. The red stele is best seen in the spring up to the time of fruiting. No other disease of strawberry produces this symptom. The red stele fungus is introduced into new planting sites mainly through the distribution of infected plants. Zoospores are motile and swim about when soil moisture is high.
Zoospores invade the tips of young fleshy roots.
As soil temperatures rise, the fungus forms large numbers of oospores in the stele of infected plants. These oospores survive periods of hot, dry and freezing weather for several years in the soil. Disease cycle of Red Stele Rot on strawberry. We wish to thank the New York State Agricultural Experiment Station for use of this figure. Figure taken from the Small Fruit IPM Disease Identification Sheet No. 2.