CRITICAL WEED FREE PERIOD
The goal in managing weeds is to maximize yields - by suppressing weed competition during critical periods of crop development.
This concept is called the Critical Weed-Free Period, when it is most important to control weeds to prevent competition with crops. It is important to understand these facts about the Critical Weed-Free Period:
- If the crop is kept weed-free for the Critical Weed-free Period, no yield reduction should occur.
- Weeds emerging after the Critical Weed-Free Period will not affect yield.
- When weeds are allowed to compete with crops during the Critical-Weed Free Period, the effects may last over several years in perennial crops, especially weeds during the establishment year.
| Critical Weed-free Periods for grapes | |
| Grapes, new plantings | First 8 to 12 weeks immediately after planting. |
| Grapes, 2nd and 3rd year | First six weeks after bud break, then mid-August to first frost. |
| Grapes, bearing | Mid-June through mid-July, mid-August through harvest. |
There are other valid reasons to control weeds outside of these critical periods such as:
- Weeds present in late season can severely hinder the ability to complete hilling to protect graft unions from winter injury. Weeds left uncontrolled in hills in spring can hamper the effectiveness of dehilling procedure to expose graft union and prevent scion rooting,
- Weeds present during the mid-August onwards period may serve as reservoir location for aphids and Multi-Coloured Asian Lady Beetle,
- Weeds may hamper harvest,
- Uncontrolled weeds in the vineyard may serve as a source of weed seeds for the future.
Controlling weeds outside of the CRITICAL WEED-FREE PERIOD will NOT increase yields.
