Although farming is a year-round activity, many critical crop and weed management decisions are made in spring. The following tips will help successfully manage weeds and secure a good harvest.
- Establish a healthy crop: A well-established and healthy crop that develops a uniform stand is the most effective tool against weeds. Use the best available agronomic practices to get an early start and a close crop canopy. Studies show that a highly competitive crop shades out late emerging weeds, reducing the need for rescue treatments and the overall cost of herbicides.
- Match problems to solutions: Periodic scouting determines what weeds are present. Be aware that “windshield scouting” will not give a precise assessment of the various weed species in fields, their size, location and density. Producers need to walk or four-wheel drive their fields in a systematic pattern.
Read Also
VIDEO: Green Lightning and Nytro Ag win sustainability innovation award
Nytro Ag Corp and Green Lightning recieved an innovation award at Ag in Motion 2025 for the Green Lightning Nitrogen Machine, which converts atmospheric nitrogen into a plant-usable form.
Take a field map and trace the location of different weed patches. This map may allow you to spot treat a field instead of using a blanket application.
- Proper timing: Periodic scouting can better determine the most appropriate time to implement a weed management practice.
If early-emerging species such as prickly lettuce, common lamb’s-quarters, field pennycress or common sunflower are dominant, postponing planting will allow you to eliminate these seedlings with tillage or herbicides. Conversely, early planting is a reasonable approach to managing late-emerging species such as morning glory, yellow foxtail and common cocklebur. The early planting lets the crop get ahead of the weeds.
Be aware that postponing postemerge treatments too much with the goal of controlling late emerging weeds may result in higher herbicide rates. There may also be significant yield reductions because of early season competition.
- Calibrate the sprayer: Growers usually calibrate their equipment to make sure they apply the correct amount of litres per acre. However, individual nozzle output may vary. Nozzles may over-apply by 10 to 30 percent because of poor calibration and worn tips.
Although checking each individual nozzle takes time, it will result in more accurate applications and reduce the risk of weed escapes or crop injuries.
- Check the weather: An actively growing weed is a key factor to getting good control, whatever the herbicide. It may be necessary to wait until temperatures and moisture conditions are suitable to achieve good control.
As a general rule, burn-down herbicides should not be applied when temperatures are in the low teens or upper 20s. Likewise, do not spray
postemergent herbicides after a prolonged dry period or when temperatures are in the high 30s.
- Know your soil: Soil-applied preplant incorporated and pre-emerge herbicides are valuable tools to manage early season weeds and if they are residual, can provide season-long weed control. However, miscalculations could cause crop injury or fail to control weeds.
Soil factors that determine the concentration and persistence of soil-applied herbicides include texture, acidity (pH), moisture and organic matter. As a general rule, soil high in organic matter or clay may require higher rates or more frequent herbicide applications than sandy and coarse soil. Also, the risk of herbicide carryover varies with soil pH.
- Avoid cosmetic control practices: The main goal of a weed management should be to secure crop yields. Before managing weeds, take into account that factors such as soil moisture, weather and crop and weed stages will influence a weed’s competitiveness.
Late emerging weeds tend to have little or no impact once the crop has formed a closed canopy. Thus,
postemergent control practices should be concentrated during the early stages of crop development.
However, extremely large and heavy infestations should not be tolerated. This is particularly true when dealing with highly competitive and difficult-to-control weeds such as Canada thistle and field bindweed.
- Work against herbicide resistance: Weeds, like any other living organisms, are variable. Some of them have an innate ability to survive and reproduce after a treatment with a dose of herbicide that would normally be lethal.
Every time you apply a herbicide, you are killing the susceptible plants and selecting potential herbicide resistant individuals. If you repeatedly use the same herbicide for several years, you are increasing the selection pressure and speeding development of herbicide resistant weeds.
To reduce this risk, rotate among herbicides with different modes of action, applied either as tank mixes, premix formulations or sequential applications. Also, rotate management practices, such as timely cultivation. Crop rotation is an excellent tool to reduce selective pressure on herbicide resistant weeds.
- Minimize weed seed production: An old proverb says: “one year’s seeding, seven years weeding.” Weeds can produce a couple of hundred to many thousands of seeds per year. Preventing seed production is a key component in developing a successful long-term weed management program. This is particularly true when dealing with weed species that have a persistent seed bank such as field pennycress and common lamb’s-quarters.
- Be a good neighbour: Building a strong relationship with neighbors, local extension agents, chemical dealers and seed representatives can help make sound decisions and save money. You might benefit from early pay and bulk discounts. Also, they are an invaluable source of information on new alternatives to manage weeds.
A good weed management program starts with a healthy crop. Integrating practices is essential to increasing the program’s success and securing high yields.
