Crop Crop ProductionProduction

Erik L. StrombergErik L. Stromberg, Professor and Extension Plant , Professor and Extension Plant Pathologist, Agronomic CropsPathologist, Agronomic Crops

Department of Plant Pathology, Physiology and Department of Plant Pathology, Physiology and Weed ScienceWeed Science

Virginia Polytechnic Institute and State Virginia Polytechnic Institute and State UniversityUniversity

Blacksburg, Virginia 24061-0331Blacksburg, Virginia 24061-0331

Plant Pathogens as a Threat Plant Pathogens as a Threat to Crop Productionto Crop Production

Susceptible host cropSusceptible host crop Large acreageLarge acreage Conducive environmentConducive environment Virulent pathogenVirulent pathogen Trade restrictionsTrade restrictions

Attributes of a Pathogen Attributes of a Pathogen for Bioterrorism for Bioterrorism (N. Schaad, et.al. APS(N. Schaad, et.al. APSnetnet, 15 , 15 Sep-31 Oct 1999)Sep-31 Oct 1999)

Produces a toxinProduces a toxin Easy to obtain, handle, and deliverEasy to obtain, handle, and deliver Easy to grow in large amountsEasy to grow in large amounts Highly infectious under many Highly infectious under many

conditionsconditions Results in the establishment of a Results in the establishment of a

quarantinequarantine No chemical control or resistance No chemical control or resistance

availableavailable

Attributes of a Pathogen Attributes of a Pathogen for Bioterrorism for Bioterrorism (continued)(continued)

No method for rapid or reliable No method for rapid or reliable detectiondetection

Infects systemically by natural Infects systemically by natural meansmeans

Spreads quickly by natural meansSpreads quickly by natural means Causes severe crop lossesCauses severe crop losses Survives long periods or is persistentSurvives long periods or is persistent

Strategies for Assuring Strategies for Assuring Crop BiosecurityCrop Biosecurity

Prevention --- focused on increased Prevention --- focused on increased security, secrecy, and border security, secrecy, and border protection.protection.

Preparedness --- focused on early Preparedness --- focused on early detection, rapid diagnosis, and detection, rapid diagnosis, and

rapid rapid recovery.recovery.

Increasing Preparedness Increasing Preparedness Through Investments in Through Investments in InfrastructureInfrastructure

Strengthen Diagnostic Laboratories Strengthen Diagnostic Laboratories --- --- Plant Clinic (VPI & SU) and Plant Clinic (VPI & SU) and VDACSVDACS

Coordinate and communicate with Coordinate and communicate with others states’ diagnostic laboratoriesothers states’ diagnostic laboratories

Information sharing --- balance Information sharing --- balance between confidentiality and public between confidentiality and public access access

Increasing Preparedness Increasing Preparedness Through Investments in Through Investments in InfrastructureInfrastructure (continued) (continued)

Training of first responders --- early Training of first responders --- early detection and reporting of detection and reporting of

novel or novel or unfamiliar pest or disease unfamiliar pest or disease outbreak.outbreak.

Workshops, short-courses for Workshops, short-courses for county county agents, agronomists, seed agents, agronomists, seed

inspectors, agri-business inspectors, agri-business personnel, personnel, etc.etc.

Increasing Preparedness Increasing Preparedness Through Investments in Through Investments in Infrastructure Infrastructure (continued)(continued)

Investments in basic research --- Investments in basic research --- genomics and biotechnology --- genomics and biotechnology --- National Plant Genome Initiative.National Plant Genome Initiative.

Development of host plant Development of host plant resistance resistance novel approaches.novel approaches.

Discover novel genes in pathogens Discover novel genes in pathogens as as the basis for new diagnostic the basis for new diagnostic tools.tools.

Potential Pathogen Threats to Potential Pathogen Threats to Virginia Crop ProductionVirginia Crop Production

Soybeans --- Soybean rustSoybeans --- Soybean rust Corn --- Maize Streak VirusCorn --- Maize Streak Virus Wheat --- Karnal buntWheat --- Karnal bunt

Soybean RustSoybean Rust Caused by the rust Caused by the rust

fungus, fungus, Phakospora Phakospora pachyrhizipachyrhizi

China, Australia, China, Australia, Korea, India, Japan, Korea, India, Japan, Thailand, Philippines, Thailand, Philippines, Nepal, Brazil, Nepal, Brazil, Argentina, Paraquay, Argentina, Paraquay, South Africa, South Africa, Zimbabwe, Nigeria, Zimbabwe, Nigeria, Mozambique, Mozambique, Rwanda, and UgandaRwanda, and Uganda

Photo: USDA, APHIS, PPQ

Soybean Rust Soybean Rust (continued)(continued)

Discovered in Discovered in Hawaii in 1995.Hawaii in 1995.

Wind-borneWind-borne Causes defoliationCauses defoliation Losses range from Losses range from

10-90% in the 10-90% in the countries where countries where the rust occurs.the rust occurs.

Photo: USDA, APHIS, PPQ

Soybean Rust Soybean Rust (continued)(continued)

A virulent race A virulent race would cause large would cause large crop and crop and economic losses.economic losses.

No resistance in No resistance in current cultivarscurrent cultivars

Fungicides (none Fungicides (none currently currently registered in U.S.)registered in U.S.)

Photo: USDA, APHIS, PPQ

Maize Streak VirusMaize Streak Virus GeminivirusGeminivirus Vectored by a Vectored by a

leafhopper, leafhopper, Cicadulina Cicadulina mbilambila

Endemic to Africa and Endemic to Africa and adjacent Indian Ocean adjacent Indian Ocean islands.islands.

Reported from Reported from Australia, Bulgaria, Australia, Bulgaria, Egypt, France, Egypt, France, Hungary, India, Hungary, India, Pakistan, YemenPakistan, Yemen

Photo: E.L. Stromberg, KwaZulu-Natal, Republic of South Africa

Maize Streak Virus Maize Streak Virus (continued)(continued)

All U.S. germplasm All U.S. germplasm is highly is highly susceptible.susceptible.

Early infection Early infection results in a sterile results in a sterile plant.plant.

Potential for Potential for tremendous losses.tremendous losses.

Photo: E.L. Stromberg, KwaZulu-Natal, Republic of South Africa

Maize Streak Virus Maize Streak Virus (continued)(continued)

Susceptible hosts in Susceptible hosts in

Chenopodiaceae, Chenopodiaceae, Compositae, Compositae, Gramineae, Gramineae, Leguminosae, and Leguminosae, and

SolanaceaeSolanaceae Maize field in Maize field in

ZimbabweZimbabwe Early infectionEarly infection No grain yieldNo grain yield

Photo: E.L. Stromberg, Maize infected with Maize Streak Virus, Zimbabwe

Karnal BuntKarnal Bunt Caused by the Caused by the

smut fungus, smut fungus, Tilletia indica Tilletia indica ((Neovossia indicaNeovossia indica))

Attacks wheat, Attacks wheat, durum wheat, and durum wheat, and triticaletriticale

Seeds have an Seeds have an offensive “fishy” offensive “fishy” odorodor

Photo: University of Idaho

Karnal Bunt Karnal Bunt (continued)(continued)

Spreads movement Spreads movement of infested wheat of infested wheat seed, plants, straw seed, plants, straw or through soil on or through soil on equipment.equipment.

Grain losses are Grain losses are not significantnot significant

International International QuarantineQuarantine

Wheat infected with Tilletia indica Photo by Lisa Castlebury

Karnal Bunt Karnal Bunt (continued)(continued)

Currently in parts of Currently in parts of Mexico (’72), Pakistan, Mexico (’72), Pakistan, India, California (’97), India, California (’97), Arizona (’96), and Arizona (’96), and Texas (’01).Texas (’01).

Although causes Although causes virtually NO IMPACT on virtually NO IMPACT on crop production it is crop production it is important because of important because of international trade international trade restrictions on wheat restrictions on wheat from areas where the from areas where the disease occurs.disease occurs.

Photo: Texas Department of Agriculture

Karnal Bunt Karnal Bunt (continued)(continued)

Unlike many other bunt or smut diseases of Unlike many other bunt or smut diseases of cereal crops, it cannot be easily controlled. cereal crops, it cannot be easily controlled.

Conventional methods such as seed Conventional methods such as seed treatment fungicides and certified seed are treatment fungicides and certified seed are not effective once the fungus is established not effective once the fungus is established in a field.in a field.

No commercial varieties of common wheat No commercial varieties of common wheat in the US are thought to have adequate in the US are thought to have adequate resistance to karnal bunt. Durum (pasta) resistance to karnal bunt. Durum (pasta) wheat is somewhat resistant.wheat is somewhat resistant.

Karnal Bunt Karnal Bunt (continued)(continued)

USDA-APHIS has localized quarantines to USDA-APHIS has localized quarantines to prevent movement of infested grain and prevent movement of infested grain and machinery from the affected areas.machinery from the affected areas.

More than 70 countries, including the US, More than 70 countries, including the US, have quarantine restrictions on imports of have quarantine restrictions on imports of grain with karnal bunt. Many have a zero grain with karnal bunt. Many have a zero tolerance standard for spores of tolerance standard for spores of T. indicaT. indica. .

Efforts to convince our trading partners to Efforts to convince our trading partners to relax the international quarantines on relax the international quarantines on karnal bunt have not yet been fruitful.karnal bunt have not yet been fruitful.

Threats to Crop Threats to Crop Production?Production?

The potential is real whether by The potential is real whether by the acts of man or nature.the acts of man or nature.

Need for Communication, Need for Communication, Detection, Diagnosis, Remediation.Detection, Diagnosis, Remediation.

Research on pathogens and host Research on pathogens and host resistance will reduce the threat resistance will reduce the threat and impact.and impact.