Moist conditions bring out crop diseases

A fungus is among us or at least that is the fear for many farmers these days. Rain is always welcome, but in the moist conditions fungus, rust or root rot are bound to rear their ugly heads among crops this spring.

A fungus is among us or at least that is the fear for many farmers these days. Rain is always welcome, but in the moist conditions fungus, rust or root rot are bound to rear their ugly heads among crops this spring.

NDSU Dickinson Research Extension Center Agronomist Roger Ashley has talked with producers and plant specialists about the possibility of fungus or rust.

"Some leaf rust was found in southeast North Dakota so rust may be found in this area in the not-to-distant future," Ashley said. "Rust can not be controlled with rotations. Rust spores blow in from the south of us. Some varieties of spring wheat are more resistant to rust than other varieties because of genetics."

Rust was found last Friday in Ransom and Cass counties. Even those varieties resistant to rust one year may not be the next year because rust constantly evolves to survive. Varieties once resistant to a race of rust may not be to the new race, he added.

The fungus tan spot is one of those who have enjoyed the recent rainy weather. It is generally found with wheat or wheat conditions, but can move to other crops if wheat was the residue crop.


"Wheat on wheat is conducive to tan spot," Ashley said. "Sixty-five percent of wheat in the state is grown on last year's wheat residue. Whether it's durum or spring wheat on wheat or whatever combination of wheat, it can produce tan spot which can be controlled with crop rotation."

Tan spot is an early season disease, he added. Tan spot appears on the leaf in a tannish-dark circular spot with a halo around it.

"It definitely likes the moist weather and cooler temperatures we've been having," Ashley said. "Later on in the season, producers will want to look out for septoria which also is a fungal disease that likes warm, moist conditions, but is not usually a problem around here."

Septoria looks like oblong or irregular lesions on the plant dark in color with an irregular shaped halo.

The month of May has had above normal precipitation while April's precipitation was average, he added.

"If we have average or above average in June we could see septoria," Ashley said. "Also later in the season is rust on leaves or stems, but we don't have the alternate host, which is (the shrub) Barbary."

The fungicides that control tan spot or septoria also control rust. Adding fungicide to the herbicide tank applied at this time of year will help control these diseases until the flag leaf emerges, he added.

"If disease pressure is high or expected to be high for the remaining part of the season then another application of fungicide to control rust will be needed," Ashley said. "To date, we do not have a fungicide that will control these diseases from early vegetative stages through to maturity."


Since some crops may only be at the two-leaf stage it could be another week or so before many make applications on their crops, he added.

"It's usually the first or second leaf that's got the tan spot," Ashley said. "Producers should look at the plant closely. You can't see if tan spot is there from in the tractor seat or going by in the car."

Most of the time those who have a $4.50 per acre can put on a fungicide and expect about a 4-6 bushel return for controlling tan spot, he added.

"You would get the same or better results in terms of yield with better crop rotation," Ashley said. "Propkonzial is the generic name, but it used to be called Tilt. Both are part of many more products available."

There are seed treatments that help with root rot, but don't completely solve the problem, he added.

"Tan spot, fufarium root rot and phythium are bad. Those root diseases cause more problems with wheat on wheat situations than any other," Ashley said. "With tan spot, other grasses can get it. If you were to look at smooth broom grass, chances are you'd see pretty big lesions from tan spots with dark circles and yellowish-purple halos."

Ashley converses with other NDSU Extension Service professionals about the ongoing problems of plant diseases. He continues to visit with producers about what they can do and goes out to take a look at the crops with them.

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