“This makes it difficult for breeders to keep up in releasing stripe rust resistant varieties,” Wright said.

Stripe rust spores are wind-borne and can travel hundreds of miles on the currents. The fungus grows only on living host plants and survives between seasons on volunteer wheat, barley plants, and some wild grasses. Rust spores are spread by wind to initiate infections. Disease development is most rapid at temperatures of 50-60 F (10-16 C) with intermittent rain and dew, although the disease can continue to develop at higher temperatures and drier conditions; secondary cycles occur at seven to 10-day intervals. Wright says new stripe rust spores develop in the Sacramento Valley and are flown into the Central Valley on the wind.

Stripe rust was first identified in California in 1993-1994.

Growers would be wise to plant resistant varieties, but they may not be available and growers have no alternative but to plant susceptible varieties and hope stripe rust does not make an appearance as it did in 2003 when yields losses were as high as 75 percent from stripe rust.

The disease developed early that year and was more severe than normal throughout much of the U.S. A combination of very mild winter temperatures (particularly December through January) and early sowing resulted in very early infections, about six weeks earlier than normal for California’s Central Valley. Cool conditions persisted much longer in the spring than usual, and stripe rust reached very high levels throughout the Central Valley.

Wheat is susceptible from as early as January and as late as April, says Wright.

If a grower is cursed with a susceptible variety and stripe rust blows in, Wright recommends 10 percent hot spots on leaves to trigger a fungicide application.

There are five registered fungicides in California that will control stripe rust: Stratego, Tilt, Quadris, Quilt and Headline.

These varieties are classified as “highly susceptible”: Yecora Rojo, Dirkwin, Joaquin, Mika Bonus, Brooks, Anza and Blanca Grande.

“Susceptible” are WB-Paloma, Pacheco and Summit.

“Moderately Susceptible” are Red Wing, Kronos, Duraking, Clear White and WB-Cristallo.

“Moderately resistant” are PR 1404, Trical 118, Westmore, Ultra, Camelot, Crown, Platinum, Topper, Blanca, Fuerte, Volante, Trical 105 and Desert King.

“Resistant” are Cal Rojo, Blanca Grande 515, Summit 515, Fortissimo, Lariat, Lassik, Patwin, Blanca Royale and WB-Rockland.