Losses caused by uncontrolled weed growth are measured in billions of dollars per annum.
| Table 1. Annual losses
in potential production of three crops due to various agents. |
| Crops |
Potential
production (Mt) |
Losses
(Mt) due to: |
| Pests |
Diseases |
Weeds |
| Cereal |
1468 |
204 (40%) |
135 (27%) |
167 (33%) |
| Sugar crops |
1330 |
228 (36%) |
232 (37%) |
175 (26%) |
| Vegetables |
280 |
23 (29%) |
31 (40%) |
24 (31%) |
Annual losses of crops to weeds, pests and diseases differ depending on the crop
(See Table 1) and geographic region (See Table 2). Some of the greatest losses are recorded in the tropics where good growing conditions and poor weed control measures result in good weed establishment. British agriculture has spent in excess of $250 million per year from 1980 to 1990 on herbicides to alleviate damage that would otherwise be caused by weeds. This outstrips that
spent on either insecticides or fungicides.
| Table 2. Annual losses in production
due to various agents in different parts of the world. |
| |
Percentage losses due
to: |
|
Area |
Pests |
Diseases |
Weeds |
| Worldwide |
14 |
12 |
10 |
| Europe |
5 |
13 |
7 |
| North America |
9 |
11 |
8 |
| Africa |
13 |
13 |
16 |
| Asia |
21 |
11 |
11 |
The specific problems that weeds cause can be placed in the categories listed to
the left.
Steve Adkins
