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Many nonnative or alien insect pests, disease-causing
pathogens, and weed pests of food, fiber, nursery crops,
pasture, and range, and many nonnative pests and foreign
diseases of poultry, livestock, and other animals (including
zoonotic pathogens that can cause disease in animals and
humans) pose threats to U.S. agriculture. Examples of
pests and diseases include Mediterranean fruit fly (Medfly),
citrus canker, Asian longhorn beetle, foot-and-mouth disease,
karnal bunt wheat fungus, exotic Newcastle disease of
poultry, and leafy spurge, each of which raises concerns
about economic or environmental losses. More information
on plant pests can be found on the APHIS/National Agricultural
Pest Information System (NAPIS) website,
while more information on foreign animal diseases can
be found on the APHIS/National Center for Animal Health
Surveillance website,
and in Foreign Animal Diseases The
Gray Book.
In 1999, Executive
Order 13112 defined an invasive species as:
- One that is nonnative, alien, or exotic to the ecosystem
under consideration, and
- One whose introduction causes, or is likely to cause,
economic or environmental harm or harm to human health.
In addition, the definition considers the costs and benefits,
or net damages, of an alien species, since the benefits
of some nonnative species, including some crops, livestock,
and ornamental plants, exceed the costs.
Economic Issues
Invasive species increasingly pose potential and actual
economic threats to U.S. agriculture and other sectors
of the economy. This is generating renewed interest in
policies to address the threats. Several factors
bolster the need to further these efforts.
- Rapid growth in USDA's
emergency program expenditures beginning in
the late 1990s, signaling an increasing budgetary burden
from APHIS responses to outbreaks with serious consequences
- Expansion in the flow of imported
goods and travelers into the United States—a
key pathway for the introduction of invasive species
- Increased vulnerabilities from the changing structure
of livestock and crop production in the United States
- Increased likelihood of invasive species survival
during transit due to faster modes of transport for
people and goods
- Growing evidence of adverse impacts of species on
native ecosystems
- Increased restrictions on traditional chemical control
options
The ERS Program of Research on
the Economics of Invasive Species (PREISM) focuses
on economic issues related to nonnative pests of agricultural
significance or pests that fall under USDA/APHIS and other
USDA programs, a subset of invasive species. While such
pests can affect agricultural production or trade, some,
such as cheatgrass or spotted knapweed, can affect nonagricultural
systems as well. The ERS program focuses on pests that
have entered the United States (or have moved outside
their natural range in the United States) and potential
pests that have not yet entered.
Some nonnative species can damage U.S. agriculture by
reducing crop and livestock production or threatening
export potential, with impacts on U.S. prices, consumers,
and trade. Some species have a particularly high potential
for damage because, once introduced in the United States,
they lack natural enemies and their populations can increase
and spread to levels that are difficult and costly to
eradicate. As international trade is a potentially
key conduit of movement of pests between countries, the
presence of some pests in the United Stated could cause
some countries to stop importing U.S. products or require
the goods to undergo special inspections, treatments,
or mitigation programs before entry.
In addition, U.S. producers, other businesses, APHIS,
and State governments incur costs to prevent or reduce
such losses. APHIS and State Governments managing
invasive species face these economic questions:
- How should resources be allocated among exclusion,
surveillance, control, or restoration programs?
- Which pests should be excluded or controlled?
- What type of exclusion or control approach should
be used (such as monitoring, eradication, containment,
or long-term areawide management programs)?
- When and where should the approach be used?
- What type of practice should be used (such as inspection,
pesticide, biological control)?
- When should a program or use of a practice be terminated?
Information about potential economic consequences of
pests and the costs and benefits of public programs to
control them can help inform decisions to manage invasive
species. Complicating these decisions are uncertainties,
or lack of knowledge, about key variables: the likelihood
of pests entering and establishing damaging populations,
the speed with which populations can grow, their ability
to spread long distances, and the extent of damages they
can cause to agriculture and ecosystems.
Asian Soybean Rust: Effects of a New Pest Introduction
Asian soybean rust (rust), Phakopsora pachyrhizi,
is an invasive plant pathogen with the potential to cause
major damage to U.S. soybean production. Soybean yield
reductions and production cost increases have been attributed
to rust in Africa, Asia, Australia, and South America.
P. pachyrhizi is a virulent fungal pathogen that
can travel long distances rapidly in wind currents and
storms. Moreover, it can infect over 95 species of plants,
including soybeans, peas and beans, and wild hosts such
as kudzu, which has been an efficient source of inoculum
in Brazil. The detection of rust in South America during
2000 heightened concerns regarding its threat to U.S.
agriculture.
Developing a response to the potential entry of this
pest onto U.S. soil became a major concern of USDA.
In Economic
and Policy Implications of Wind-Borne Entry of Asian Soybean
Rust into the United States (April 2004), ERS examined
potential economic and environmental impacts of rust epidemics
of varying degrees of severity. ERS estimated that
acres planted to soybeans would decline between 2 and
6 percent (later confirmed by 2005 producer planting intentions)
and that the annual sum of producer losses in domestic
crop and livestock sectors and consumer losses would vary
widely between $200,000 and $2 billion, depending on the
geographical extent and severity of the rust epidemics.
In fall 2004, rust was detected in Alabama, Arkansas,
Florida, Georgia, Louisiana, Mississippi, Missouri, South
Carolina and Tennessee. Fungal spores apparently
arrived from South America, likely carried by winds accompanying
Hurricanes Francis and Ivan. In response to these
detections, USDA, in cooperation with State agriculture
departments and universities, the United Soybean Board,
and the private sector, established a coordinated
framework for soybean rust surveillance, reporting,
forecasting, research, and education to enhance the ability
of U.S. producers to cost-effectively manage the pest.
Sentinel soybean plots are planted in potential spore
source areas in southern States and other major soybean
producing States. Sentinel soybean, bean and kudzu plots
are monitored for evidence of rust. Confirmed outbreaks
are reported on the USDA
Public Soybean Rust Website. Computer models
forecast when and where rust outbreaks may occur. Soybean rust was detected in 19 States in 336 counties in the continental United States in 2007, but severe rust epidemics did not occur. By the end of 2007, the presence of rust had been confirmed in 53 counties in Georgia, 40 in Alabama, 37 in Missouri, 33 in Arkansas, 26 in Mississippi and Texas, 24 in Florida, 21 in Louisiana, 14 in Iowa, 12 in Oklahoma, 9 in Kansas and Virginia, 7 in South Carolina and Tennessee, 6 in North Carolina, 4 in Illinois and Nebraska, 3 in Kentucky, and 1 in Indiana.
 d
The estimated cost of setting up and running the coordinated
framework ranged between $2.6 million and $5.0 million.
In The Value of Plant
Disease Early Warning Systems: A Case Study of USDA's
Soybean Rust Coordinated Framework (April 2006), ERS
found that the value of the framework to U.S. soybean
producers may vary between $11 million and $299 million,
depending on the degree to which the information resolved
producer uncertainty regarding the occurrence of rust.
The value of information provided by early-warning systems
depends on the availability of preventative control measures
to manage rust outbreaks and on the sensitivity of producer
pest-control responses to information to update estimates
of the likelihood of disease occurrence.
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