Introduction

37
THESE TABLES SHOULD BE USED ONLY AS A GUIDE.
The figures are based on Western Canadian research trials and will not be accurate all of the time. The yield loss values apply
only to healthy, well fertilized crops with good stand establishment. Crops that are diseased or emerged unevenly will not
compete well with weeds and will suffer larger yield losses than indicated in these tables. The yield loss figures are based
on competition from single weed species only. Other weeds, such as wild mustard or Canada thistle, must be controlled if
the figures are to be accurate. As well, the tables are based on competition from normal height crops. Semi-dwarf or hybrid
varieties may not compete as well with weeds and the figures may not be accurate in these cases.
Table 1. Yield Losses (Percent) in Wheat Caused by Wild Oats.
Wild Oat Density – Number Per Square Metre
1 2 4 6 8 10 12 14 16 18 20 25 30 35 40 45 50
Wild Oats are 1 Leaf Stage
Ahead of the Crop
1 2 4 6 8 10 12 14 15 17 19 22 26 29 32 34 37
Wild Oats are the Same
Leaf Stage as the Crop
1 1 2 4 5 6 7 8 9 10 11 14 16 18 20 2 24
Wild Oats are 1 Leaf Stage
Behind the Crop
0 1 1 2 3 3 4 5 5 6 7 8 10 11 13 14 15
Source: O’Donovan, Alberta Environmental Centre (Vegreville, Alberta)
Weed Control
Figure 1. Spray Decision Guideline for Wild Oats in Wheat.