As if the drought were not enough to reduce forage yields this year, some Sacramento Valley oat hay growers have been hit with a bad case of Barley Yellow Dwarf Virus (BYD) disease this spring, causing poor appearance and low yields.

Symptoms of BYD include reddening of the leaves, stunting of plants, and irregular and small or blank seed heads. The virus is only transmitted by aphids, which acquire the virus from wild grasses. The presence of the virus does not affect the feeding quality of the forage.

Controlling the aphids to prevent infection is possible, but not generally effective or cost efficient. Early planting favors aphid movement into fields, so later plantings (around 15 November in the Yolo County area) to escape aphid flights might reduce the probability for infection.

California Red is a very old variety that is still used by some growers for planting, but it is known to be highly susceptible to BYD. Since BYD on oat often causes the leaves to turn red, that may be a reason for California Red's name, along with the reddish seeds. California Red also has a minor vernalization (cold) requirement and typically fall-planted cereals receive enough cold during the winter to satisfy any winter chilling needs. This past winter was unusual, being warmer than normal, and spring-habit wheat and oat headed almost 3 weeks before normal. Lines with vernalization requirement (need a cold period for flowering) headed about 10 days later than normal.

All oat varieties can be infected with BYD virus, but some varieties are more tolerant than others and are significantly better than California Red. Newer varieties released in 2007 by UC Davis are described below (2012 UC Davis Agronomy Progress Report on Oats, http://agric.ucdavis.edu/). The varieties are later in maturity than California Red or Montezuma, but the hay tonnage is higher. Variety selection is an important tool to combat BYD infections. In each case below, we are comparing the variety with ‘Montezuma' (but compared with ‘Curt' for forage quality).

UC 113, UC 128, UC 148 oats have been under production and certification by Baglietto Seeds. UC 132 has been under production and certification by Lockwood/Barkley Seed. Howard (UC 142) is not licensed and available from the UC Davis Foundation Seed Program.

• UC 113: Heading later, 4-5 inches shorter. Excellent straw strength, thicker. Barley yellow dwarf virus, moderately susceptible under severe infection conditions, tolerant in most environments. Crown rust moderately resistant, stem rust resistant. Equivalent hay yields. Higher crude protein, lower acid and neutral detergent fiber percentage. 

• UC 128: Heading later, 8-10 inches taller. Excellent straw strength, thicker. Barley yellow dwarf virus, moderately resistant under severe infection conditions, resistant in most environments. Crown and stem rust moderately resistant. Hay yields: 128%. Higher crude protein and comparable acid detergent fiber, but higher neutral detergent fiber percentage.

• UC 132: Heading later, 5-8 inches shorter. Excellent straw strength, thicker. Barley yellow dwarf virus, moderately susceptible to under severe infection conditions, resistant in most environments. Crown rust resistant, stem rust susceptible. Hay yields: 109%. Higher crude protein and comparable acid and neutral detergent fiber percentage.

• UC 148: Heading later, 3 inches taller. Good straw strength, thicker. Barley yellow dwarf virus, moderately susceptible under severe infection conditions, resistant in most environments. Crown rust resistant, stem rust susceptible. Hay yields: 105%. Higher crude protein and comparable acid detergent and higher neutral fiber percentage.

• Howard (UC 142): Heading similar (early), 8 inches shorter. Good straw strength, thinner. Barley yellow dwarf virus moderately resistant. Crown rust and stem rust, resistant. Hay yields: comparable. Higher crude protein percentage and comparable acid detergent fiber and higher neutral detergent acid percentage.