The challenge with developing a management strategy for wheat disease in East Texas is predicting springtime weather. If producers knew early in the season what the weather would be as wheat enters the most vulnerable stage, they could judge whether to apply a preventive fungicide or just wait and see.
Farm Press asked Jim Swart, Texas AgriLife Extension Integrated Pest Management Specialist, to explain the best management practices for wheat disease control in East Texas.
Question: Jim, can you give us an overview of the wheat disease complex likely to affect whet in the region?
Swart: Leaf rust and stripe rust are both common in the area. Stripe rust is typically the first disease threat we have in northeast Texas, but the varieties we plant in this area are resistant to stripe rust, so we do not have a big problem with it. If a variety is susceptible to stripe rust, we don’t recommend it. Leaf rust likes warmer conditions and shows up when wheat begins to head.
Question: Is variety resistance the best option?
Swart: Farmers in the area plant mostly six wheat varieties, which have some host plant resistance to leaf rust, which comes later in the spring. But that may not be adequate.
Question: What do you recommend?
Swart: This year, I recommend a preventive treatment. Based on the value of wheat (up to $8 per bushel) applying the fungicide, even with a low level of leaf rust infection, is justified. I would spray everything. The material will cost about $4 per acre (some reports indicate an even lower cost); application cost adds another $4 per acre.
Question: What advantage can growers expect from a fungicide?
Swart: The break-even yield increase would be one bushel of wheat (assuming $8 a bushel), and that’s easily achieved, even with low disease pressure. At 25 percent infection level at physiological maturity, we typically see a 1- to 2-pound increase in test weight with the fungicide application.
At 50 percent infection, we see a moderate yield increase and another one pound improvement in test weight. With anything higher than 50 percent infection rate, we see a 3- to 4-fold return on the investment with a tebuconazole application. Fungicide use may increase straw strength and standability. “Also, just a small level of disease infection can reduce test weight by 1 pound. Fungicide gives us better quality and better yield — it’s a no brainer with $8 wheat.
Question: What about scouting and spray as needed?
Swart: With the current wheat price and the low cost of control, a wait-and-see approach may not be as beneficial as a preventive treatment.
Question: What fungicides do you recommend?
Swart: Tebuconazole, available under several brand names, is the least expensive treatment for both leaf rust and stripe rust in wheat.
Question: Is this new to the market?
Swart: The product has been around for a long time. We’ve been testing and using it since 1984, and it controls rust as well now as it did then. We’ve probably done more work with foliar fungicides in wheat than anyone in this part of the country.
Question: What are the advantages of this fungicide?
Swart: Tebuconazole is the cheapest and most effective product we have. It’s as good as anything available for leaf rust, and as good as or better than anything for stripe rust.
Question: What’s your application recommendation?
Swart: Late March to early April is time to start spray applications to control leaf rust. Farmers should begin tebuconazole applications when the flag leaf is fully emerged (Feekes 9) up to heading. That usually gives us 35 to 40 days of control, enough to mature out the grain.