UNL CropWatch Oct. 18, 2010: Rust Developing in Alfalfa

UNL CropWatch Oct. 18, 2010: Rust Developing in Alfalfa

Oct. 18, 2010

Warm, humid weather has caused rust to form in many alfalfa fields throughout the region.

Rust doesn't overwinter here and rarely infects alfalfa here before mid-July, but with humid conditions like we've had this year, rust can be blown up from the south and infect fields.

Rust usually causes little damage in fields harvested monthly, but alfalfa that is more mature or alfalfa grown for seed can be injured and defoliated by rust, greatly reducing seed yield and quality. Thus, early harvest is one means to minimize damage.

One of our biggest concerns is that infected seedlings can be weakened and not develop as much winterhardiness as normal, making them more susceptible to winterkill. In this case, plan to monitor these fields closely next spring to determine early if you need to change your cropping plans.

Remember, since rust can't be economically controlled, the best management options are to monitor, harvest, and adjust plans to minimize damage.

Problems with Feeding Rust-Infected Hay

Rust-infected hay sometimes causes allergic reactions in animals, more often with horses than with ruminant livestock. Rust also lowers the
digestibility of hay, and this lower energy value often isn’t detected well by standard laboratory tests. If you feed rust-infected hay, animals may not get as much energy from it as expected.
 

Bruce Anderson
Extension Forage Specialist

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