Timely pest control applications can help to increase winter wheat yields.
by Joyce Tredaway Ducar
The best yields I ever made in wheat averaged 107 bushels per acre, and they were made when I did just a few things differently than in the previous year.
First, I controlled my weeds, particularly ryegrass. We have many options to use these days when it comes to ryegrass control. An option that is not normally used for any crop but rice is a delayed pre-emergence that is labeled for two products in wheat.
A delayed pre-emergence is when 80 percent of the wheat seeds have germinated but have not yet broken through the ground. You can determine this by digging up your seeds and seeing if they have germinated and calculating the percent of the ones that you count.
Two products that have a delayed PRE label for ryegrass control include Anthem Flex (Group 14,15) and Zidua (Group 15). Early post-emergence ryegrass options include Anthem Flex (Group 14 and 15), Osprey (Group 2), Powerflex (Group 2), Axial XL (Group 1), Axiom (Group 5 and 15) and Zidua (Group 15). However, Anthem Flex applied post-emergence will not control ryegrass.
If you have found that Osprey or Powerflex has not controlled your ryegrass in the past, most likely you have ALS-resistant ryegrass and need to go with a different group of herbicide to control your ryegrass. Hoelon used to be the old standard for ryegrass control, but now more than 95 percent of ryegrass is Hoelon-resistant.
Axiom contains metribuzin, and studies evaluating Zidua and metribuzin combinations revealed up to 99 percent control of Italian ryegrass throughout the season.
Broadleaf weed control is something that cannot be ignored either. Harmony Extra does a good job of controlling many broadleaf weeds in wheat, but there are some new products on the market that will work even better.
Travallas (Group 2 and 4) and Sentrallas (Group 2 and 4) are two new broadleaf herbicides that provided excellent control of cutleaf eveningprimrose and mouseear chickweed in our field trials. Quelex is a Group 2 herbicide that can be applied to wheat from the two-leaf to flag leaf emergence state. It covers a wide range of broadleaf weeds such as Carolina geranium, mustards, hairy vetch and henbit. These three new herbicides have Section 3 federal labels and are awaiting state labels for Alabama at this time.
Timely pesticide applications
After controlling weeds, making timely fungicide applications helped increase my yields tremendously. I had found that disease was bringing my yields down significantly in previous years, and two timely fungicide applications at flag leaf to booting stages and at flowering made a huge difference.
The advantage of one of your fungicide applications is that it can be made at the same time as your post-emergence herbicide application, thus reducing trips across the field. The flowering spray is for head scab and is needed if weather conditions are favorable for spreading scab. The Fusarium Head Blight Prediction Center, http://www.wheatscab.psu.edu/, provides timely information on the risk for this pathogen.
In addition, controlling aphids was essential because every year, my wheat would get barley yellow dwarf or cereal yellow dwarf, diseases caused by viruses spread by aphids. Controlling aphids at the right time minimizes the spread of the viruses.
The following recommendations apply to wheat that is planted at the recommended planting date for grain in Alabama: Oct. 15-Nov. 10 in north Alabama, Oct. 15-Nov. 15 in central Alabama, and Nov. 15-Dec. 1 in south Alabama.
In north Alabama, an insecticide seed treatment at the aphid rate, or a foliar spray with a pyrethroid insecticide 30 days after planting, gives the best economic return. In south Alabama, the foliar insecticide is most likely to pay off when it is applied in late winter (late January or early February). It can be mixed with the liquid nitrogen application that is applied at that time.
In central Alabama, it may be necessary to control the aphids in fall and late winter. If the forecast is for a warm winter, the additional effort to control aphids in the fall in central Alabama is more likely to pay off.
There is always a risk from Hessian fly, so rotating your wheat and choosing a Hessian fly-resistant variety is recommended. In the northern half of Alabama, cereal leaf beetles may cause problems around flag eaf and after. Scout wheat for this pest from late March through the end of April, and apply a foliar insecticide if populations exceed one cereal leaf beetle egg or larva per every two stems. Don’t let this pest get ahead of you. Once you see feeding damage on the leaves, you may have already lost some yield.
Fertilization is the third component of a high-yielding wheat crop. Making sure that the wheat had enough nitrogen fertilizer, especially in rainy years, was important. I would start out with 30 pounds of nitrogen per acre in the fall but come back and side-dress with 60 pounds of nitrogen per acre in the spring.
I always used ammonium nitrate or urea instead of liquid nitrogen, for a couple of reasons. First, you lose a fair amount of nitrogen to volatilization and as much as nitrogen costs, I wanted it all to go to the wheat.
Second, using a granular fertilizer can be useful if it isn’t raining because it will remain on the ground until a rainfall and will not be wasted. A drought-stressed plant won’t take in a liquid, so sometimes applying liquid nitrogen can be wasted money. The main reason is the stress that the liquid nitrogen puts on the wheat plant. It causes such a yellowing on the wheat, and whenever a plant is stressed, it is more susceptible to disease and insects.
Joyce Tredaway Ducar is an extension specialist and associate professor in the Department of Crop, Soil, and Environmental Sciences. Kathy Flanders, Extension specialist and professor in the Department of Entomology and Plant Pathology, contributed to the insect recommendations in this report.
