Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu; @Delmarplantdoc
Heavy rains and cooler weather over the past 3 weeks provided excellent conditions for some rarely observed, bacterial pathogens, to make guest appearances on small grains in Delaware and New Jersey. Bacteria in small grains are spread by rain splash from soil residue onto foliage, and may be brought into a field through seed. Wet, humid conditions result in enlargement of openings in the foliage that allow for exchange of carbon dioxide and oxygen. These openings serve as doorways for bacteria, which can grow and reproduce, and eventually enter the water conducting tissues of the plant. The results are long strips of “wet” tissue on foliage and occasionally stems (Figure 1 a.b). Bacterial diseases in small grains are not a major concern and typically cease to grow and persist as temperatures increase or wet conditions persist. No chemical intervention should be needed. To avoid issues in subsequent crops ensure that you are using certified disease free seed.
Elongated, water soaked lesions on barley stems and foliage caused by bacteria.
Another disease you may start seeing in fields at low levels in Barley Yellow Dwarf. This is a virus carried by several species of aphids, and transmission dynamics are extremely complicated and related to aphid dynamics, viral types present in said aphids, time of infection, and variety of wheat or barley planted in fields. It is far past the time when this disease infected your fields, and management is not warranted. BYDV can be observed as small patches of plants with shorter stature and often foliage with red or orange leaf tips. Infection in the fall, the previous year, is mostly associated with significant yield losses. Maintaining good rotations, managing volunteer weeds, especially grasses, and planting varieties with good BYDV tolerance can impact any potential yield impact caused by this virus.
Wheat showing symptoms of BYDV infection. Note red leaf tips.