| PROPOSED
MEASURES: PESTS, DISEASES, AND INVASIONS |
Crops lost to
pests such as insects, weeds, nematodes and diseases, because these
factors reduce crop yields and quality and are the subject of major
deterrent efforts. (Fig. 1)
Percentage of
cropland treated with pesticides, as an indication of the severity
of pressure from various pests. This is a surrogate for more direct
measures of pest impacts. (Fig. 2)
Resistance to
pesticides. Exposure to pesticides can lead to resistance in pest
populations, reducing the effectiveness of chemical controls. (Fig.
3)
Interceptions
of nonnative pests at U.S. ports, as an indication of the level
of introduction of pests with the prospect of causing significant economic
damage. This is a surrogate for more direct measures of the level of
nonnative pests in U.S. agriculture. (Fig. 4)
Treatment for weeds
is very common in all regions of the United states, applied to an average
of 57 per cent of all harvested croplands. Treatment for insects, diseases,
and nematodes is generally less common but varies greatly by region.
Treatment for insects, diseases, and nematodes is most common in the
Southeast and Pacific regions.
Pest
Loss Example: Wheat Losses to Leaf and Stem Rust (1) Technical
Note
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Source:
USDA Agricultural Research Service
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| Because there
is no consistent national information on pest losses, losses of
wheat from leaf and stem rust are presented as an example. This
graph illustrates that even for a single crop such as wheat, the
interaction between host, pathogens, and environment changes significantly
over time, with different pests contributing more or less to overall
losses at different times. |
Percentage
of Cropland Treated for Weeds, Insects, Diseases, or Nematodes,
(1997) (2) Technical
Note
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Source:
USDA, National Agricultural Statistics Service
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| Chemical
Pesticides are not the only deterrents available to farmers. Pest-resistant
varieties, crop rotation, sanitation measures, biological controls,
and natural defenses are also components of many pest management
programs. |
| Interceptions
of Nonnative Pests of Commercially Valuable Crops At Ports-of-Entry
During 1997 (4) Technical
Note |
|
Crop
|
Insects
and Similar Invertebrates
|
Diseases
|
Weed
Seeds
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|
Corn
for grain
|
417
|
1
|
1
|
|
Soybeans
for beans
|
3
|
0
|
3
|
|
Wheat
(all)
|
32
|
7
|
4
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|
Alfalfa
|
17
|
0
|
1
|
|
Cotton
(all)
|
3
|
1
|
0
|
|
Tobacco
|
0
|
0
|
0
|
|
Grapes
|
2
|
0
|
0
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|
Potatoes
|
145
|
1
|
0
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Citrus
(all)
|
2,333
|
844
|
1
|
|
Pome
fruits (apples+pears)
|
228
|
6
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0
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Total
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3,180
|
860
|
10
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Notes:
Totals include all interceptions, regardless of species. Thus,
the number of different species intercepted is less than the number
of interceptions shown here. Screening includes only pests that
are potential threats to major agricultural crops, not for pests
that might have damage other ecosystem components
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Source:
USDA, Animal and Plant Health Inspection Service
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| STATUS
OF TECHNICAL DATA & OTHER NOTES |
No consistent
or comprehensive national information is available on losses of
crops to pests or diseases. Determining crop losses is difficult
because crop yields are influenced by many factors; furthermore,
many problems are difficult to diagnose, and there is no uniform
reporting system. Estimates indicate that fewer than 1 per cent
of crops have losses from weeds that exceed 30 per cent; for 70
per cent of all crops, losses are estimated at less than 10 per
cent.
No consistent
or comprehensive national information is available on pesticide
resistance. Surveys indicate that resistance exists in at least
394 insect species and similar invertebrates, 71 weed species,
and 160 plant diseases. Resistance to multiple pests has been
reported. These data are from multiple sources; there are no uniform
procedures for determining or reporting resistance.
Evaluations
of pesticide application and nonnative pest interception information
would be enhanced by analyses of time trends. Trend data are available
and is expected to be included in future reports.
Information
on nonnative pests is from a continuing program of the USDA Animal
and Plant Health Inspection Service. Only pests that are potential
threats to significant agricultural crops are counted. Trend information
is available and is expected to be included in the 2001 report.
Please see
the Technical
Notes for additional information.
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