Why Control Weeds Early?
- Early control helps protect yield potential of the crop.
- Small weeds are easier to control.
- Young weeds absorb and translocate herbicides better.
- Herbicides can be less effective during times of heat and drought stress, which often occur at later application times.
Sequential weed control programs, including preplant/preemergence (PRE) followed by postemergence herbicides, have consistently provided the best weed control and greatest net returns.
Field with heavy infestation of dandelion and horseweed. Existing weeds should be controlled prior to planting to improve planter performance and help the crop get the best possible start.
Critical Period of Weed Control
- Defined as the growth stages or time during which weeds must be controlled to maintain maximum yield potential. Assumes the field is clean at planting time.
- Corn: weeds can reduce yield as soon as the V2 stage. Control weeds earlier than this and maintain control through at least V14 to help ensure maximum yield potential.
- Soybean: control weeds within the first 4 weeks. Maintain control through canopy closure.
Preventing weed seed production: Control weeds to minimize competitive effects but also to prevent seed production, especially for glyphosate-resistant weeds like waterhemp, Palmer amaranth and ragweeds.
Take the Time to Apply Preplant/PRE Herbicides
- Weeds that germinate, emerge and grow with the crop cause the most yield loss.
- Preplant/PRE herbicides provide critical early season weed control when crops are most sensitive to competition.
- Preplant/PRE herbicides can widen the window of application for postemergence herbicide sprays.
- Total post programs are more risky because weather conditions may prevent timely application.
- Control weeds before they start to compete.
If Preplant/PRE Herbicides Were Not Applied:
- Apply postemergence herbicides as soon as possible.
- Include residual herbicides to extend control of weeds that are still germinating.
- Do not cut the use rate. Use the recommended rate for the weed size.
- Use high-quality adjuvants as directed on the product labels.
- Be prepared to apply follow-up treatments to control escapes and late-germinating weeds.
Corn field showing the effects of weed competition on corn growth (right side of field). The grass weeds have been sprayed and are dying, but corn growth is significantly reduced and yield potential is lower compared to the left side of the field.
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