By Blake Jackson
Alfalfa production in Kentucky can be affected by numerous diseases throughout the growing season, with disease development depending on weather conditions, the presence of harmful pathogens, and the susceptibility of the alfalfa variety being grown.
According to Kiersten Wise, Julie Beale, Shane Bogle, and Nick Roy of the University of Kentucky, disease outbreaks occur only when these three factors align, making environmental conditions a major influence on disease pressure.
Rather than following a fixed calendar, alfalfa diseases appear when favorable conditions exist. Still, certain diseases are more common during specific seasons. In the spring, growers should inspect fields for winter injury and disease damage.
Fall-seeded fields may suffer from Sclerotinia crown and stem rot, while wet soils often encourage root diseases such as Aphanomyces, Pythium, Phytophthora, and Rhizoctonia.
Cool, wet weather can also trigger foliar diseases including Leptosphaerulina leaf spot and spring black stem.
During the summer months, crown rot problems may continue, especially in poorly drained fields. Warm and humid weather creates ideal conditions for summer black stem, Stemphylium leaf spot, common leaf spot, and anthracnose to develop and spread.
In the fall, some leaf diseases remain active, while crown rot symptoms may persist. Sclerotinia crown and stem rot is especially common during this period and may continue into late fall if moisture and temperatures remain favorable.
Effective disease management relies on integrated cultural practices rather than chemical treatments alone. Farmers are encouraged to plant certified disease-resistant varieties, maintain proper soil fertility and pH, use treated seed when appropriate, and establish crops in well-drained fields.
Timely harvesting, crop rotation, and careful field sanitation can also reduce disease pressure. Although fungicides are available for some foliar diseases, their performance and economic return are often uncertain, making prevention and sound management practices the best long-term strategy.
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Categories: Kentucky, Crops, Alfalfa