Crop Production

1. Crop Production Erik L. Stromberg, Professor and Extension Plant Pathologist, Agronomic Crops Department of Plant Pathology, Physiology and Weed Science Virginia Polytechnic Institute and State University Blacksburg, Virginia 24061-0331

2. Plant Pathogens as a Threat to Crop Production • Susceptible host crop • Large acreage • Conducive environment • Virulent pathogen • Trade restrictions

3. Attributes of a Pathogen for Bioterrorism (N. Schaad, et.al. APSnet, 15 Sep-31 Oct 1999) • Produces a toxin • Easy to obtain, handle, and deliver • Easy to grow in large amounts • Highly infectious under many conditions • Results in the establishment of a quarantine • No chemical control or resistance available

4. Attributes of a Pathogen for Bioterrorism (continued) • No method for rapid or reliable detection • Infects systemically by natural means • Spreads quickly by natural means • Causes severe crop losses • Survives long periods or is persistent

5. Strategies for Assuring Crop Biosecurity • Prevention --- focused on increased security, secrecy, and border protection. • Preparedness --- focused on early detection, rapid diagnosis, and rapid recovery.

6. Increasing Preparedness Through Investments in Infrastructure • Strengthen Diagnostic Laboratories --- Plant Clinic (VPI & SU) and VDACS • Coordinate and communicate with others states’ diagnostic laboratories • Information sharing --- balance between confidentiality and public access

7. Increasing Preparedness Through Investments in Infrastructure (continued) • Training of first responders --- early detection and reporting of novel or unfamiliar pest or disease outbreak. • Workshops, short-courses for county agents, agronomists, seed inspectors, agri-business personnel, etc.

8. Increasing Preparedness Through Investments in Infrastructure (continued) • Investments in basic research --- genomics and biotechnology --- National Plant Genome Initiative. • Development of host plant resistance novel approaches. • Discover novel genes in pathogens as the basis for new diagnostic tools.

9. Potential Pathogen Threats to Virginia Crop Production • Soybeans --- Soybean rust • Corn --- Maize Streak Virus • Wheat --- Karnal bunt

10. Soybean Rust • Caused by the rust fungus, Phakospora pachyrhizi • China, Australia, Korea, India, Japan, Thailand, Philippines, Nepal, Brazil, Argentina, Paraquay, South Africa, Zimbabwe, Nigeria, Mozambique, Rwanda, and Uganda Photo: USDA, APHIS, PPQ

11. Soybean Rust (continued) • Discovered in Hawaii in 1995. • Wind-borne • Causes defoliation • Losses range from 10-90% in the countries where the rust occurs. Photo: USDA, APHIS, PPQ

12. Soybean Rust (continued) • A virulent race would cause large crop and economic losses. • No resistance in current cultivars • Fungicides (none currently registered in U.S.) Photo: USDA, APHIS, PPQ

13. Maize Streak Virus • Geminivirus • Vectored by a leafhopper, Cicadulina mbila • Endemic to Africa and adjacent Indian Ocean islands. • Reported from Australia, Bulgaria, Egypt, France, Hungary, India, Pakistan, Yemen Photo: E.L. Stromberg, KwaZulu-Natal, Republic of South Africa

14. Maize Streak Virus (continued) • All U.S. germplasm is highly susceptible. • Early infection results in a sterile plant. • Potential for tremendous losses. Photo: E.L. Stromberg, KwaZulu-Natal, Republic of South Africa

15. Maize Streak Virus (continued) • Susceptible hosts in Chenopodiaceae, Compositae, Gramineae, Leguminosae, and Solanaceae • Maize field in Zimbabwe • Early infection • No grain yield Photo: E.L. Stromberg, Maize infected with Maize Streak Virus, Zimbabwe

16. Karnal Bunt • Caused by the smut fungus, Tilletia indica (Neovossia indica) • Attacks wheat, durum wheat, and triticale • Seeds have an offensive “fishy” odor Photo: University of Idaho

17. Karnal Bunt (continued) • Spreads movement of infested wheat seed, plants, straw or through soil on equipment. • Grain losses are not significant • International Quarantine Wheat infected with Tilletia indica Photo by Lisa Castlebury

18. Karnal Bunt (continued) • Currently in parts of Mexico (’72), Pakistan, India, California (’97), Arizona (’96), and Texas (’01). • Although causes virtually NO IMPACT on crop production it is important because of international trade restrictions on wheat from areas where the disease occurs. Photo: Texas Department of Agriculture

19. Karnal Bunt (continued) • Unlike many other bunt or smut diseases of cereal crops, it cannot be easily controlled. • Conventional methods such as seed treatment fungicides and certified seed are not effective once the fungus is established in a field. • No commercial varieties of common wheat in the US are thought to have adequate resistance to karnal bunt. Durum (pasta) wheat is somewhat resistant.

20. Karnal Bunt (continued) • USDA-APHIS has localized quarantines to prevent movement of infested grain and machinery from the affected areas. • More than 70 countries, including the US, have quarantine restrictions on imports of grain with karnal bunt. Many have a zero tolerance standard for spores of T. indica. • Efforts to convince our trading partners to relax the international quarantines on karnal bunt have not yet been fruitful.

21. Threats to Crop Production? • The potential is real whether by the acts of man or nature. • Need for Communication, Detection, Diagnosis, Remediation. • Research on pathogens and host resistance will reduce the threat and impact.