Dry field conditions mean the wheat disease stripe rust is at a 20-year low, a researcher  says.

“Overall, it’s bad news for growers because of the lack of moisture,” said Xianming Chen, plant research geneticist for the USDA Agricultural Research Service in Pullman, Wash. “Most fields we check, it looks quite dry.”

Stripe rust needs moisture to spread and infect other plants, Chen said. Cold weather in February reduced the amount of rust that survived over the winter.

Chen believes growers are planting fewer wheat varieties that are susceptible to stripe rust, but he hasn’t yet tallied the number of acres.

Farmers are advised to spray fungicide only if they’re raising susceptible wheat varieties under irrigation. Irrigated wheat production is primarily in the Moses Lake, Wash., area, Chen said. Growers should check their fields if they’re not past the flowering stage, and spray if they see stripe rust. If not, there’s no need to spray, he said.

The rust will return, Chen said. It also has the ability to infect grasses, but grass infections are also low due to the dry conditions, he said.

Rust is severe in winter and spring cereal nurseries on the western side of the region, as is common. Farmers typically spray fields with fungicide several times there, Chen said.

Chen expects rust inoculum to continue to be low for the fall. It could increase if weather conditions turn favorable for the disease, he said.

The amount of rust was low in 2019, but still more than this year, Chen said. Last year, the disease was a bigger problem, he said.

Wheat stripe rust has been reported in 12 states: Louisiana, Texas, Washington, Oklahoma, Tennessee, Arkansas, California, Oregon, Mississippi, Kansas, Nebraska and Ohio.

Barley stripe rust has been reported in Washington, California and Oregon.