On Wednesday morning, stripe rust was found in Louisiana by Boyd Padgett, LSU AgCenter plant pathologist. Shortly thereafter, Padgett spoke with Delta Farm Press about the find. Among his comments:
On where the rust was found…
“It’s in an experimental line I use specifically for testing fungicides. This particular breeding line was being increased for commercial release before the new race of stripe rust that occurred in Ark-La-Miss last year took it out. So, it’s a variety that never made it into the commercial arena because of its susceptibility.
“We were spraying some tests this morning at the Macon Ridge Research Station. I found it when we were walking around.
“We’ve seen very low levels of rust in that field. It’s very hard to find – probably less than 1 percent.”
That’s low incidence so what advice are you giving farmers?
“We’re telling growers to keep an eye out, especially in varieties that are known to be susceptible to the stripe rust pathogen.
“Hopefully, most of the varieties our producers are growing have resistance to this disease. We do know that growers scrambled to find wheat seed last fall. So there are probably some fields of older varieties and varieties we would not normally grow in Louisiana.
“The varieties that (Dr. Stephen) Harrison (LSU AgCenter wheat breeder) has released have very good genetic resistance to this rust, but the pathogen has changed and some previously resistant varieties may no longer have effective resistance.
“Right now, though, we’re still a bit early on the early side as far as making a fungicide application. If growers do find rust in their fields, and they’re approaching flag-leaf, they may consider an application.
“In south Louisiana, some wheat is probably approaching flag-leaf. Farther north, in my plots, it’s just past jointing.”
On the rust’s earliness…
“This is on the early side. But we’ve seen it this early before so it isn’t extremely surprising.
“Recently, we’ve had cool, wet weather. Now, there have been no rains but there have been heavy dews.
“I was talking to a colleague recently and said ‘these dews are ideal for stripe rust.’ At mid-day, leaves can still be wet with dew. So, just because we haven’t had rain in a long time, stripe rust can still find a way. We are expecting rainfall this weekend.
On spraying a fungicide…
“It varies with the variety, but it’s usually mid-March before fungicide applications start going out.
“A farmer may be thinking ‘well, I’m going to go ahead and spray.’
“But we’ve done work for several years spraying resistant varieties knowing there is disease all around but not in that particular field. We don’t see a response to fungicides. Susceptible varieties are a different story.
“So, unless a farmer actually has disease in the field, they probably don’t need to spray.
“I haven’t seen any other diseases in the fields, yet. I thought we might find some powdery mildew, but no.”