380 - Early Season Weed Control Strategies
"Timely Weed Control to Maximize Crop Potential" is one of the Gold Standards that is essential to maximizing your on-farm profits. Good weed management begins with three things: timing, timing and timing! All shareholders have access to the same herbicides and research and rate information and have similar equipment but what sets apart those that successfully control weeds from those that don’t is usually timeliness. More often than not, that first herbicide application sets the stage for the rest of the season. Shareholders that successfully control weeds spray when the weeds are small. If rain and wet soils prevent ground spraying, aerial application must be considered.
"Why is weed control so critical?" Figure 1 shows yield reduction due to pigweed and wild oat competition. It doesn’t take much weed competition to significantly reduce your sugarbeet yield.
Early season weed control encompasses three distinct areas: 1) Pre-plant 2) Pre-emerge and 3) Post-emerge weed control.
- Mechanical - field cultivation, seedbed preparation, etc. This will take out any early germinating weeds.
- Chemical- use of a soil applied herbicide such as RoNeet, Eptam or Nortron. This may or may not be effective depending on soil moisture conditions.
- Chemical – use of a non-selective herbicide such as Roundup or Gramoxone Extra is an excellent strategy when controlling early season weeds such as kochia. Resistant kochia will be a "real" problem in the Valley this year and a pre-emerge strategy using Roundup or Gramoxone Extra may be prudent. Be very careful that no beets have emerged when using either of these products!
Comparing Roundup to Gramoxone Extra
| ||Nonselective||Translocated||Control Annuals||Control Perennials||Carryover||Need Surfactant*|
*Use of a surfactant is necessary with both products to ensure adequate uptake of the chemical. Some formulations of Roundup may already contain a surfactant. Use of ammonium sulfate at 17 lbs./100 gallons of water with Roundup will improve the consistency of weed control.
- Mechanical – a rotary hoe or a harrow can go a long way in reducing early weed pressure and herbicide costs. It’s important though that the sugarbeet plants are large enough and plant population is high enough to withstand a possible reduction in stand.
- Chemical – here your options vary somewhat based on the weeds that you are trying to control. Micro-rates have opened up a new dimension in weed control.
- It’s possible to spray throughout the day with minimal crop injury.
- Another good strategy to adopt is spraying an 11" band but be sure to get uniform coverage.
- Broadcast applications can be made and may be a good option the first time over to ensure good weed control and to minimize the need for cultivation.
- For micro-rates to be effective, you need to spray a minimum of 3 times at 5-7 day intervals, use about 10 gallons of water/acre, and try to target small, cotyledon sized weeds. Use of windshields is also recommended.
Sample of a Micro-rate mix (broadcast):
- Betamix or Betanex @ 8 fl. oz./ acre or Progress @ 5.7 fl. oz./acre.
- UpBeet @ 1/8 oz./acre.
- Stinger @ 1.3 oz. /acre (if needed).
- Methylated seed oil @ 1 1/2% volume to volume (1 pint/acre minimum).
- Quad 7 or other basic blend adjuvant @ 1 1/2% volume to volume if used.
- Note: If using both MSO and Quad 7 – the combination should equal 1 ½% v/v.
- Optional: Assure II @ 4 oz./acre, Select @ 2 oz./acre or Prism @ 4 oz./acre or Poast @ 5.3 oz./acre (for grass control).
- Note: New label allows rate increases on larger beets.
Be sure to consult your agriculturist to determine whether your weed population warrants the use of all products. Overuse of Stinger can result in beet damage.
Micro-rate Mixing Order:
- Begin with a clean spray tank.
- Fill spray tank with 1/3 of the total amount of clean water needed.
- Slurry UpBeet in hot water or pH adjusted water at pH 8-9. Quad 7 (or other basic blend adjuvant) would be added to tank here if used. Household ammonia can be used to modify pH also.
- Add UpBeet to spray tank.
- Fill tank to 2/3’s full – add Betamix, Betanex or Progress followed by Stinger then modified seed oil. Add remaining water.
- Gentle agitation results in less precipitation. Do not let solution sit in tank for any length of time.
Following the aforementioned guidelines will result in successful weed control this spring. Good Luck and if you have any questions, contact your agriculturist. This issue prepared primarily by Blayne Doty, Project Agronomist.