Submitted By: Jennie Mazzone, Penn State Extension Educator, Horticulture
Strawberries are a high-value crop, but diseases can quickly reduce yield and fruit quality if problems go unnoticed. Regular scouting and accurate diagnosis are key to identifying problems early and managing diseases effectively in your berries.
Scout your fields at least once or twice per week. When you notice a problem, walk the field carefully and look for patterns. Are the affected plants in a low-lying part of the field? I am always on alert for Phytophthora root and crown rot in low-lying, waterlogged areas. Are entire plants collapsing or just certain leaves? The vascular wilt fungus Verticillium commonly wilts and dries outer leaves first, leaving younger inner leaves green and turgid, at least at the onset of disease. Look closer when you see spots and blotches for signs of a pathogen. The Phomopsis leaf blight fungus will make black, round fruiting bodies within V-shaped lesions that can be seen with a hand lens (Figure 1).
Diseases often appear in patches, localized to one or a few locations, and will spread over time, while abiotic problems are usually more uniform and develop after a known stress, like frost injury. To complicate matters, there are situations where abiotic issues, like winter injury, weaken plants and invite secondary infections. Strawberry plantings are often affected by multiple, overlapping issues rather than a single issue, requiring growers to identify all contributing factors for effective management.
Some strawberry diseases may look alike but require different management approaches. Both angular leaf spot and leaf scorch can produce necrotic spots on leaves in advanced stages. However, their early lesions differ distinctly. Angular leaf spot, caused by a bacterium, begins as water-soaked lesions that develop a translucent, “windowpane” appearance when leaves are held up to the light. In contrast, leaf scorch, caused by a fungus, develops small purple lesions that remain opaque throughout. Because fungicides used for leaf scorch will not control angular leaf spot, accurate diagnosis is critical to avoid ineffective treatments, wasted time, and unnecessary costs. When in doubt, contact your local Extension office or submit a sample to the Penn State Plant Disease Clinic for diagnostic support and management recommendations.
To help growers sharpen their diagnostic skills, Penn State Extension is hosting a Strawberry Disease Identification for Commercial Growers workshop on July 7 from 9:00 a.m. to 12:00 p.m. at the Southeast Agricultural Research and Extension Center. Participants receive a high-quality hand lens and a photo disease guide to use during the training and take back to the farm. Space is limited for this hands-on workshop. Don’t miss this opportunity to strengthen your diagnostic skills! Register online at https://extension.psu.edu/strawberry-disease-identification-for-commercial-growers or call 1-877-345-0691.
Improving your disease identification skills pays off by leading to effective controls, fewer unnecessary inputs, and healthier berries overall.
