Would be, could be, should be a record year for wheat, unless it rusts.

This year's wheat crop across the Panhandle is in excellent condition, said Dr. Brent Bean, Texas Cooperative Extension agronomist here. With help from May rains, it should be the best in years, he said.

Insect and virus diseases have been minimal, Bean said, but "we are seeing more fungal diseases, due largely to the wetter-than-normal weather."

These include septoria, powdery mildew, leaf rust and stripe rust, he said. Most serious are the rusts.

"The wet weather this last weekend, along with the potential for more rain this week, could potentially cause an explosion in the incidence of wheat rust in many Panhandle fields," Bean said.

Stripe rust is relatively new to the Panhandle, showing up in a few fields three years ago, he said. Now it is the dominant rust in the area. It looks similar to leaf rust, but the rust postules tend to line up between the leaf veins, giving it a striped appearance.

Stripe rust will thrive in temperatures of 46 F to 58 F when moisture is present on the leaves, Bean said. In contrast, leaf rust prefers warmer conditions and will thrive in temperatures around 70 F.

Researchers believe there are varietal differences in tolerance to leaf and stripe rust. However, data collected in South Texas suggests all varieties are now susceptible.

However, Bean said, the rust strains in the Panhandle could still lend themselves to some varietal resistance. Recent observations made by Dr. Calvin Trostle, Extension agronomist in Lubbock, and others suggests some leaf rust resistance of Cutter and Jagalene varieties.

Producers must answer several questions when deciding the best way to manage rust. Oklahoma research indicates a minimum per acre yield of 40 bushels per acre and a price of at least $3-$3.50 per bushel is necessary to justify spraying fungicides, Bean said.

A fungicide application will likely cost about $16.50 per acre, he said. Spraying fungicide will not increase yields, but will preserve yield potential, research shows.

Timing, also, is important.

The flag leaf contributes as much as 75 percent or more of grain yield, according to research. So keeping it healthy is important to realizing grain yield potential, Bean said. For example, wheat at flowering with 40 percent of the flag leaf covered with leaf rust has an estimated yield loss of 20 percent.

Two fungicides for leaf and stripe rust control are sold under five trade names: triazole (Tilt, Propimax), strobilurin (Headline, Quadris), or a combination (Stratego, Quilt).

To protect yield potential, consider spraying when the flag leaf fully emerges to flowering to full boot and milk, Bean said. Sprays at soft dough and hard dough don't offer much control.

If leaf rust is already present, earlier spraying is probably warranted, provided the yield potential criteria are met, Bean said. Waiting until all flag leaves are fully emerged risks infection of leaf rust on the flag leaf, and fungicides work best at prevention rather than curing an existing problem, he said.

The amount of leaf rust infection will be reduced when conditions are dry and warm, Bean said. Anticipating weather favorable to rust development on the flag leaf is the most important factor, he said.

"We believe the window of effective control is at least 14 days and an additional level of control may be available up to 21 days," after spraying, Bean said. A second spraying, even in fields with a high yield potential (greater than 70 to 80 bushels per acre) is seldom justified, he said.

One option is to spray a half rate of fungicide early and apply a second half two weeks later. This should give longer overall protection, he said.

For the latest research, go to: http://amarillo.tamu.edu/programs/agronomy/publications/Wheat/