The fungus Sphaerotheca macularis , appears as a greyish-white coating on the undersides of leaves late in red or purple in color. Leaf function is impaired but symptoms develop so late in the season that plant vigor is seldom affected. There are several virus diseases that can infect strawberries. Visible symptoms may not be evident in the plants. Plant vigor is generally affected, how-ever, causing the plants to die when weather conditions become unfavorable.
Visible symptoms can include leaf crinkling, variegation, cupping, and stunting.
Plants showing these symptoms should be removed and destroyed. The main symptoms are stunting and yellowing of leaf margins. Purchase only certified virus-free strawberry plants. Many strawberry viruses are transmitted by aphids. The only way to assure that the plants remain reasonably virus-free is to carry on an aphid spray control program throughout the growing season.