Thursday, February 20, 2003 EMERGING PLANT

Agricultural Outlook Forum 2003

Presented: Thursday, February 20, 2003

EMERGING PLANT PATHOGENS AND PESTS: PREVENTION, PREPAREDNESS AND PRIORITIES Jacqueline Fletcher1 and Doug Luster2 President and Chair 2 , Ad hoc Emerging Diseases and Pathogens Committee The American Phytopathological Society (APS) 1

I. What are introduced species? “If a pest can enter the United States, over time, it will find a way here.” –D. Huber et al., 2000. Invasive Pest Species: Impacts on Agricultural Production Natural Resources and the Environment; Council for Agricultural Science and Technology. Some insects and pathogens have been introduced from outside our national borders intentionally, for positive purposes such as the biocontrol of weeds, or because the species represented a potentially valuable new commodity. More often, pests are introduced unintentionally, “hitching a ride” with introduced crop species or commodities, lurking in travelers’ luggage or clothing, adhering to boat or airplane surfaces, or naturally, for example, blowing in with hurricanes or swept across borders by the wind. This type of threat is even greater now with burgeoning international travel, trade and transportation. Finally, we are much more conscious in 2003 of the potentia l that pathogens or pests might be introduced intentionally for harmful purposes including bioterrorism and biowarfare. The threat of introduced pathogens and pests is significant. About a fourth (550 of the 2000 known) of the potentially damaging ‘exotic’ plant pathogens pose significant new risks to U.S. agriculture. II. Crop vulnerability U.S. agriculture represents 13% of gross domestic product and 17% of the nation’s employment. Agriculture is vulnerable to emerging pathogens and pests, partly because it is so valuable. The vulnerability of our agricultural interests stems partly from the huge acreage devoted to these resources. Crops, forests and rangeland cover 1 billion acres of our country’s land, much of which is not continually monitored. To find a new disease or pest at its early stages in such a vast area is much like the proverbial “spotting a needle in a haystack.” For this reason, long lag periods (weeks or years in some cases) may occur between the introduction of a pathogen and detection, identification, and response. For example, the recent outbreak of citrus canker in Florida, first diagnosed in 1995, was probably due to an introduction of the causal bacterium two years earlier. Similarly, plum pox, discovered in Pennsylvania in 1999, is now thought to have been introduced several years earlier. Our valuable plant commodities are susceptible to many domestic and foreign pathogens. Many crop species, bred for consistent quality and high yield, are planted as monocultures. The low genetic diversity of many of our crop species increases their vulnerability to pests and pathogens. About 65% of U.S. crop losses are due to introduced pathogens, amounting to an estimated cost of $137 billion/year! Pathogens and pests cross borders easily, making the risk of an introduction into our neighbor’s fields a risk to our country as well. These factors lead to major challenges for every facet of disease and pest management: protection, detection, diagnosis, forensics, and eradication/control. I will present three brief cases of introduced pathogens and pests to highlight some of the critical issues and needs.

Case#1. Citrus canker in Florida: It’s not just a question of juice Citrus is an $8.5 billion crop in Florida, and citrus canker is one of its most damaging diseases. Caused by a bacterium, Xanthomonas axonopodis, this disease has appeared in Florida several times over the years. In the mid-1980s the disease devastated many acres of citrus orchards. A major problem in that epidemic was the inability of the diagnostic test available at the time to distinguish between the canker bacterium and another, closely related, but non-canker bacterium. Required canker control measures had to be applied to both, at high additional cost in the case of the “interloper.” In 1995, when canker was again discovered in Florida, this time near the Miami airport, better diagnostic tools allowed precise bacterial identification. It also could be determined that the introduction was likely accidental, the bacteria probably arriving on illegal citrus cuttings in 1993. Eradication is the only effective management strategy known. Unfortunately, it is not only the trees showing symptoms that must be destroyed. Since adjacent trees are extremely likely to also harbor the pathogen they too are targeted for removal. The eradication program, implemented promptly, has cost more than $200 million and destroyed over 10 million trees so far. Despite their losses, which have been severe in some cases, Florida citrus growers understand the necessity for aggressive action. However, prominent homeowners and tourist businesses throughout the Miami area resisted the removal of landscape trees, particularly those not visibly affected. A strong citizen’s group brought suit against the management teams of the Florida Department of Agriculture and the USDA’s American Plant Health and Inspection Service, to stop the eradication program. Pending the court’s decision, all tree removal activities were suspended, and the disease continues to spread, now affecting over 1000 mi2 of urban area and orchards. Case #2. Pierce’s disease of grapes: California vineyards brace for sharpshooter Pierce’s disease poses a frightening specter to California’s $2.8 billion wine, table and raisin grape industry. Over 700,000 acres of vineyards are considered to be at risk. Although the disease, caused by the bacterium Xylella fastidiosa, has occurred in California continually since the 1880s it rarely caused significant problems because it could be transmitted only by the tiny blue-green sharpshooter, an insect capable of moving only about 3 feet. In 1999, however, the disease began to take on ominous traits, spreading much more quickly and infecting large numbers of vines. Research showed that the sudden change was due to the introduction into California of a new, aggressive insect vector, the glassy-winged sharpshooter (GWSS). Unlike its weaker blue-green “cousin”, the GWSS moves quickly and over large distances. In addition, it feeds on older, woody canes where bacterial titers are high, increasing pathogen transmission rates. Pierce’s disease management has taken a coordinated, well-funded, multi-faceted approach. Initially working separately, research and implementation groups from state, federal, academic, private and commodity entities have joined forces and are coordinated by an advisory group to maximize information sharing and efficiency. Management strategies are aimed at three different targets: the insect vector (biological and chemical control as well as novel alternative methods), the bacterial pathogen (biological, cultural and genetic controls), and the host plant (breeding for disease and GWSS resistance in grapevines). Special, targeted funding from 17 different federal and local agencies has made it possible to hire mature, experienced entomologists and plant pathologists, to explore novel control methods as well as to screen traditional ones, and to coordinate efforts with statewide symposia and dedicated databases. Case #3. Soybean rust: Are we ready for it? In 2001 the United States produced over 75 million acres of soybeans. At a total value of over $13 billion, this commodity represents the second highest value crop in the U.S.

Soybean rust, a severe fungal disease that has occurred for many years in Asia, now threatens U.S. borders. Asian production fields commonly sustain yield reductions of 10-30% because of this fungus, and losses of up to 90% have been reported. A 30% yield loss in the U.S. would cost about $4 billion in lost revenue. The causal agent, Phakopsora pachyrhizi, moved from Asia into Africa and then across the ocean to South America all within the last decade. Those monitoring the fungus’s path of destruction say about its arrival in the continental U.S.: “It’s not a question of if but of when.” Since soybean rust is not yet here, we have an opportunity and a responsibility to prepare for it. We know what is needed in a coordinated plan: 1. Early detection National surveillance Rapid diagnostics 2. Rapid response Advisories Control/management III. What can we do to protect U.S. crops against plant pathogen and pest invaders, such as soybean rust? 1. Find better ways to prevent pathogen/pest introduction and movement 2. Support new research initiatives in: Detection, diagnostics, and forensics Pathogen/pest biology and epidemiology Disease prevention and control 3. Make infrastructural changes to enhance capabilities Research needs 1. Genomic sequences of more threatening plant pathogens for: Detection - rapid, reliable; use novel sequences Forensics – trace origin and timing of initial infection Identification – identify pathogen, differentiate isolates 2. Risk-assessment (needed to prioritize efforts on high-risk pathogens and pests) More-effective procedures Additional trained personnel More international cooperation and electronic disease reporting (many diseases are in the Third World, escaping our notice) 3. Disease management New control measures (note – genomics will lead to new transgenic resistant varieties) Infrastructure needs 1. Distributed network of plant disease and pest diagnostic laboratories (recently implemented by USDA) 2. Enhanced agricultural extension infrastructure, with more agents distributed across the country – our eyes and ears in the field! 3. Central coordinating body (“CDC”-like center) 4. Coordinated network of professional societies, private industry, grower groups, state and national government entities

IV. The bottom line: 1. U.S. crops, forests and rangelands are vulnerable (this may be the most vulnerable sector of our economy) to introduced pathogens and pests – whether they are introduced intentionally or unintentionally. National needs are similar regardless of the scenario of introduction. 2. Investments in research and infrastructure are critically needed to protect these resources and respond rapidly and appropriately to the threat of introduced agents.

Emerging Plant Pathogens and Pests Prevention, Preparedness and Priorities

Jacqueline Fletcher President, APS

Doug Luster Chair, APS ad hoc Emerging Diseases and Pathogens Committee

Plant diseases are incited by a variety of microbes... Viruses

Fungi

Bacteria

nematode.jpg

Nematodes

“If a pest can enter the United States, over time, it will find a way here.” -D. Huber

Crop vulnerability • U.S. agriculture is vulnerable to emerging pathogens and pests • About 65% of U.S. crop losses are due to introduced pathogens, costing $137 billion/year • What is needed to assure the security of crops and natural resources? – Research – Infrastructure

Crop vulnerability, continued

• Crops, forests and rangeland cover 1 billion acres; to see something new at its early stages is “like spotting a needle in a haystack”

• Long periods between pathogen Plum pox virus

introduction, detection and identification, and response

Introduced species

• Some insects and pathogens are introduced intentionally, others unintentionally • 550 of the 2000 known, potentially damaging ‘exotic’ plant pathogens pose significant new risks to U.S. agriculture

Case #1. Citrus canker in Florida: It’s not just a question of juice

Citrus is an $8.5 billion industry in Florida Threat: Serious epidemic of citrus canker Problem: Diagnostics must differentiate canker vs. non-canker bacteria Citrus canker

Citrus canker: monitoring movement and rate of spread Disease spread: 1995: Discovered near Miami airport Likely from an accidental introduction on illegal citrus cuttings in 1993 Now affects > 1000 mi2 of urban area and orchards

Cooperative management program: FL. Dept. of Agriculture & Consumer Services USDA-APHIS

Gottwald et al. 2002.

Citrus canker management: eradication of diseased trees and trees within a certain radius

Goal: eradication Successful in the past and considered possible again Gottwald et al. 2002.

Growers are in favor, but homeowners are resisting.

Citrus canker: eradication facts and issues

• Cost: so far, over $200 million to destroy 10 million trees

• Disease is still spreading

Case #2. Pierce’s disease of grapes: California vineyards brace for sharpshooter

Threat: To California’s $2.8 billion wine, table and raisin grape industry Grapevine symptoms

-Over 700,000 vineyard acres at risk

History: -Bacterial disease in California since 1880s -Vector: small, weak blue-green sharpshooter -Current epidemic: new, aggressive, introduced vector, the glassy-winged sharpshooter Glassy-winged sharpshooter

Pierce’s disease management: a coordinated, well-funded, multi-faceted approach The team: State, federal, academic, private and commodity groups - coordinated

The strategies - targets: Insect vector Bacterial pathogen Plant host

The funding: 17 different agencies Cane symptoms

Case #3. Soybean rust: are we ready for it?

Rust symptoms on leaf

U.S. production area: 75 billion acres Crop value: $13 billion History of rust disease: -Long history in Asia -Yield losses 10-30% common (U.S. equivalent = $4 billion), and >90% occasional -Spread Asia - Africa - Brazil within last decade

Threat to the U.S.: Photos: G.L. Hartman

“It’s not a question of if but of when.”

Can we pre-empt soybean rust with a national plan? The plan must include:

1. Early detection National surveillance Rapid diagnostics 2. Rapid response Advisories Control/management

Spores of the rust fungus

What is needed to protect U.S. crops against plant pathogen and pest invaders?

1. Find better ways to prevent pathogen/pest introduction and movement 2. Support new research initiatives in: Detection, diagnostics, and forensics Pathogen/pest biology and epidemiology Disease prevention and control

3. Make infrastructural changes to enhance capabilities

Research needs

1. Sequences of most threatening plant pathogens for: Detection - rapid, reliable; use novel sequences • Forensics – trace origin and timing of initial infection • Identification – identify pathogen, differentiate isolates

We need new tools that are easy and fast!

Research needs

2. Risk-assessment more-effective procedures more trained personnel more international cooperation

3. Disease management new control measures

Infrastructure needs

• Network of plant disease and pest diagnostic laboratories

• Central coordinating body (“CDClike” center) • Coordinated network of professional societies, private industry, grower groups, state and national government entities

The bottom line

U.S. crops, forests and rangelands are vulnerable to introduced pathogens and pests - intentional or not.

Investments in research and infrastructure are critically needed to protect these resources and respond rapidly and appropriately to the threat of introduced agents.