September 1997

The Ryegrass Seed Game
9th Inning - Karnal Bunt

David M. Kopec, Extension Turfgrass Specialist

Over the last eighteen months, many people have heard about the Karnal bunt disease and the quarantine it caused on wheat seed leaving or entering Arizona! It reached national news headlines. Arizona is a producer of wheat for seed varieties, due to our climate and ease of isolation of pollen to protect variety integrity.

The Karnal bunt fungus is a disease which infects the seed head and turns the kernels black and sooty. The "sooty" phase is followed by the release of spores which can infect other kernels, or drop in the soil and remain for an unknown length of time. The spores undergo a change and arise as a second generation spore, which completes the life cycle (more or less). The disease is highly infectious on wheat.

Over six months ago, the Arizona Department of Agricultural (ADA) quarantined the importation of annual ryegrass, perennial ryegrass and intermediate ryegrass into our state. The reason for this was that Karnal bunt spores were found on ryegrass seed and on ryegrass plants in Oregon where the seed is grown commercially. It was unknown whether Karnal bunt on ryegrass was/is capable of infecting wheat! Therefore, the ban was made for safety sake.

Intricate tests were conducted by the USDA in the Washington D.C. area to see if ryegrass Karnal bunt (called "Bunt Lite") could infect wheat and cause Karnal bunt on wheat. For several months, everyone anticipated the results. Finally, results showed that no cross infection took place, showing the Karnal "Bunt Lite" did not cause Karnal bunt infection of ryegrass. Thus, the ADA removed the ban.

More recently, the Arizona Agriculture Council, through concerns of the Wheat Grower's Association, were/are seeking a ban on importation of ryegrass seed again. They fear potential contamination from Karnal bunt spores being brought into our state from Oregon where wheat and ryegrass fields are grown side by side. So far, no ban is in effect and commodity groups are providing their cases to the ADA. As of August 20, 1997, you can still buy turf ryegrass seed from Oregon in Arizona.

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