Red Stele of Strawberries

Above Ground: Symptoms of red stele rarely occur in the first year of strawberry growth unless plants were severely diseased before planting or if soil conditions were suitable for rapid fungal growth. Usually, red stele is first noticed during bloom of the second year. The symptoms will be most noticeable in low or soil compacted areas of a field where water drainage is poor. Strawberry plants infected with P. fragariae will show a general lack of vigor with poor runner growth and small berries. New leaves may appear bluish-green, while older leaves sometimes turn red, orange or yellow. The leaves tend to wilt during warm weather or drought stress. Severely diseased plants may collapse prior to fruiting. Although these aboveground symptoms are typical for red stele, they may resemble symptoms caused by other types of root disorders; therefore, roots also need to be examined.
Below Ground: In order to correctly diagnose red stele, strawberry roots should be sampled during early spring and summer up until the time of harvest. Samples taken after harvest are not reliable because infected roots may have already begun to decay. When taking a plant sample, dig, rather than pull the plant from the ground. Examine roots of plants which are just beginning to show signs of wilting. If red stele is present, the roots will appear unbranched and will be lacking feeder roots. This "rat-tail" appearance of the root is a diagnostic trait of red stele. Select a white root with a rotted tip and make a lengthwise cut at the point where diseased root tissue meets healthy tissue. Red stele infected roots will have a reddish-brown core, but the outer tissue will be white. The discoloration will begin at the root tip and move upwards, but usually will not move into the crowd. This is in contrast to another root disease, black root rot, in which outer root tissues are affected earlier than the inner (stele) root area. Normal roots have both a white center and outer root surface.