If you are growing a cool season forage like oats (Avena sativa) or cereal rye (Secale cereale) this year, you may have noticed some yellowing. Although there is a virus that causes this symptom (Barley Yellow Dwarf Virus), it is likely that the yellowing is the result of low soil Nitrogen due to heavy rain events this winter. The past several weeks have been fairly warm in North Central Florida and plants have been metabolizing and have an increased need for nutrients, especially Nitrogen. Nitrogen deficiency will often manifest itself in a field with uniform distribution, rather than in patches (Figure 1). The older (lower) leaves will turn yellow first and then eventually brown before the leaf falls off entirely. In a Nitrogen deficient plant, the entire leaf will be yellow with no streaking or lesions present (unless it is simultaneously infected by a pathogen). Plants may be stunted as well. Nutrient deficiencies can be easily corrected through the application of fertilizer.
Barley Yellow Dwarf Virus (BYDV) can have similar symptoms on oats and rye with a few subtle differences. With BYDV infected plants, both new and old leaves may become yellow. Also, a purple coloration may develop on some of the leaf apices. Symptom expression alone may not be enough to distinguish between a disease outbreak and nutrient deficiency. There is no curative treatment for viral plant diseases, however; it may be worth getting a diagnoses in order to plan preventative strategies for the following year. If you suspect that your plants have BYDV contact your local Extension Office or consider submitting a sample to the University of Florida’s Plant Diagnostic Center. 2570 Hull Rd. Gainesville, FL 32603. Phone: 352-392-1795.