Control Wheat Pests Early

Tip one in Phil Needham’s pest control guidelines for wheat is to get rid of weeds. No surprise there. Weeds are often top of the list when it comes to reducing the yield potential of wheat and pretty much any other crop.

“A lot of research work has been done to show that it takes just a small amount of weed growth, especially grassy weeds, to cause a significant yield loss in wheat,” says the Kentucky-based wheat agronomist and author of Taking Your Wheat Yields to the Next Level.

“If you’ve got weeds, knock them out early to reduce crop competition.” Make sure you’re using a herbicide that will control the weeds present and apply it when the weeds are small. You don’t want them sucking up soil nutrients that you want for the crop.

NEEDHAM’S OTHER WHEAT PEST TIPS

Control disease. Needham recommends you scout early for foliar diseases and consider an early-season application at the half rate. Research work within spring wheat grown in North Dakota and Montana has backed up the benefits of such applications south of the border, he says.

The decision to go with an early application, applied at the four-to five-leaf stage, will depend on thickness of the canopy, yield potential, moisture and the variety’s disease susceptibility.

Needham, originally from the U. K. and now working in the U. S., is familiar with very thick wheat crops. European farmers will apply fungicides two or more times in a single season. One may question whether this same logic would apply in Western Canada, where wheat yields tend to be considerably lower.

“The bottom line is that at the three-or four-leaf stage, a wheat plant begins to determine how many kernels sites per head it will produce,” he says. “Any stress at that stage will compromise maximum yield potential of the crop.”

Even if you don’t see any disease, Needham says some fungicides — particularly the strobilurins — can provide a “plant health” benefit that leads to higher yields. “This effect has been well researched in Europe. Wheat plants that get a strobilurin fungicide have shown to make better use of nitrogen and be more drought tolerant”.

GET GOOD COVERAGE

On the topic of disease control, you want to make sure you’re getting coverage with your fungicide. With fungicides, hitting more leaf areas means you’ll get more protection. “You want a nozzle that produces smaller droplets so you get greater coverage of the plant,” he says. “Air induction nozzles are appropriate for weed control on windy days, but with droplets of 500 to 600 microns, they don’t provide the coverage needed for fungicide.”

Needham recommends you switch to nozzles that produce droplets of 300 microns when applying fungicides. His wheat fungicide research suggests that forward/backward nozzles or European “Amistar” nozzles provide higher standards of coverage and higher yields.

Finally, you’ll want to scout for insects. “It sounds so simple, but you need to look at your fields,” he says. “Know the economic control thresholds for each insect pest and take action when the populations reach that level.”

DON’T JUST SCOUT FOR PESTS

You’ve heard the scouting message many times before. At grower meetings, Needham uses this line: “Footsteps in the fields mean higher yields.”

You need to be in wheat fields at two critical times, monitoring for insects, disease, weeds and general characteristics of crop growth. These times are emergence to jointing, and flag leaf to harvest.

Early in the season, you’re looking mostly for weeds and diseases. But you also want to look at your plant populations and consistency of emergence. For Western Canada, Needham says a population of 600 to 700 tillers per square metre is a good general target for average Prairie growing conditions. He says this may be achieved by seeding, say, 300 seeds per square metre with each plant generating two tillers. (Some emergence reductions will occur, but this gives you the general idea.) To determine tiller populations, go out when the crop is at the three-leaf stage, and count all tillers with three unfolded leaves.

Take a metre stick to the field. Count the tillers per metre of row, then multiply by the number of rows in a metre. Fewer than 600 tillers, and you’re giving up yield potential. More than that and the crop might not have the moisture to fill all the potential kernel sites. You’ll end up with light kernels, or “a 100-bushel straw with a 50-bushel yield,” Needham says.

Later in the season, you’re scouting for leaf-spot diseases, especially on the flag leaf, and for insect pests. At flowering, you’ll also want to assess the fusarium head blight risk.

*This is the third in a series of wheat management articles with Phil Needham. You can get more information at www.needhamag.com,or call 270-785-0999 to order his book called “Taking Your Wheat Yields to the Next Level — The Northern Plains edition.” Price is US$50.

Jay Whetter is the editor of Grainews.

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