Weather, harvest of spring-planted crops and myriad other reasons cause a high percentage of Southeastern wheat to be planted later than optimal in the fall.
The result is a high percentage of spring tillers that require special management to produce top yields.
Fall tillers produce bigger heads and more grain. These tillers are more drought tolerant and disease resistant. The grain in these heads is going to have higher weights, and in general, most of the profit from wheat comes from these fall tillers, according to North Carolina State University Agronomist Randy Weisz.
Spring tillers, by comparison, have a shallower root system and are susceptible to a host of production problems. “If you want spring tillers to develop, when the weather begins to warm up in February and March, you have to make nitrogen available to the plants,” Weisz says.
Unfortunately, he says, most wheat fields in February don't have enough nitrogen to do the job. To stimulate spring tiller development, the grower is going to have to make some management decisions, which cost time and money that are usually in short supply at that time of year.
Wheat fields with a majority of spring tillers are the ones most likely to need a fungicide application. Same for insecticides, Weisz contends. Cereal leaf beetles prefer spring tillers. “If you have a field planted on time, with good management practices that has predominantly fall tillers and an adjacent field with predominantly spring tillers, cereal leaf beetles will choose the spring tillers,” Weisz points out.
Cereal leaf beetles become a more troublesome pest because of their interaction with nitrogen applications. It is not advisable to add an insecticide to top-dress nitrogen. If insecticide is applied very early it will likely fail to control cereal leaf beetle and can actually increase numbers by removing predators.
Carbaryl (Sevin) formulations, though effective against cereal leaf beetle, are not suggested for cereal leaf beetle since the insecticide can stimulate aphid populations in wheat by predator removal and low effectiveness on aphids.
If threshold populations consist of near 50 percent eggs, Karate insecticide may be the best choice due to it's longer residual properties.
Wheat that was planted late in the Carolinas and Virginia is likely to not develop fall tillers, to be just spiking when cold weather starts, and these plants will stay just like that until the weather warms up. The late winter, early spring management for these fields is much different than wheat planted earlier and has a high percentage of fall tillers that are well developed, according to Weisz.
If wheat has at least 50 tillers per square foot by late January to early February, there has been fall tillering and the crop is probably in good shape.
In these fields, optimum timing for nitrogen applications is early to mid-March. If wheat doesn't have at least 50 tillers per square foot by February, that crop needs nitrogen now.
“The first problem is that most growers don't want to get down on their knees in January to count tillers,” Weisz says. A good rule of thumb that is easy to calculate is to break tillering into three categories and visually check a field in late January to early February.
If you look at a row of wheat and the plant is just beginning to spike, and only has a couple of leaves on each plant, that is about 20-25 tillers per square foot.
If there are open spaces between rows and thin spots where the rows aren't doing well, but you can see all the individual rows, that is about 50 tillers per square foot.
If the rows are closed in and the plants are thick and you can't see much ground that is about 100-150 tillers per square foot.
“If a grower has 100-150 tillers per square foot and decides the first week in February he is going to insure a good yield by applying all 100 pounds of nitrogen planned for the crop, the result will be a 100 percent chance he will have a yield decrease,” Weisz says.
“If you have wheat with plenty of fall tillers, don't put a lot of nitrogen out,” he says.
If you have less than 55 tillers per square foot, put out 20-60 pounds of nitrogen per acre to get maximum yields, then come back in March with the remainder of the nitrogen allotted to the crop.
“Rather than calculating the likelihood that early or late nitrogen applications will provide a yield boost, growers would be better off calculating what affect nitrogen application has on profit,” Weisz says.
Last year nitrogen hit a peak in price and from a profit standpoint, application of a split of 20-50 pounds provided most profit potential. If a grower says, “I don't care what the tillers look like, I'm putting out 100-110 pound of nitrogen per acre, that grower is guaranteed he would lose money,” Weisz stresses.
If a wheat grower looks at his field the first week in February and can see the rows clearly and determines there are at least 55 tillers per square foot, do not put any nitrogen down. By waiting until mid-March to put out all the nitrogen, he will insure both maximum yield and maximum profit potential, Weisz says.
On the other hand, if a grower looks at his field the first week of February and determines he has less than 55 tillers per square foot, applying nitrogen then will insure both yield potential and profitability.
Weisz also cautions growers to scout early for cereal leaf beetles. Making all the right decisions on planting date and nitrogen management can be negated by waiting until damage occurs in May. Scout in April, and if total number of eggs and larvae is greater than 25 per 100 tillers, spray for cereal leaf beetles.