Anette Phibbs, DATCP, Plant Industry Laboratory 4702 University Ave, Madison WI Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Reports /  Corky Ringspot Survey  Powdery Scab Survey

Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Corky Ringspot Survey Corky Ringspot Disease in the US California, Florida, Idaho, Washington Oregon Michigan Minnesota Wisconsin (N. C. Gudmestad, I. Malik and J.S. Pasche, Plant Disease (2008) 92(8):1254) A. Phibbs

Tobacco Rattle Virus (TRV) and Nematodes TRV is transmitted by Stubby root nematodes Trichodorus spp. and Paratrichodorus spp. These nematodes are present in Wisconsin. Hosts range is huge: potatoes, tomatoes, peppers, including many weeds, annuals and perennials (white & red clover, oats). Non-hosts are alfalfa, corn, barley, rye, wheat, carrots and pumpkin. Nematodes in a 1.5ml tube. Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Corky Ringspot Survey ¼ inch A. Phibbs

Astilbe Peony Barrenwort Coral bells A. Phibbs Hosta Bleeding heart Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report Perennials Infected with Tobacco Rattle Virus

Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Corky Ringspot Survey Symptoms of CRS include necrotic brown rings in Ranger Russet. Photo courtesy of Jim Crosslin, USDA-ARS, Prosser, WA Brown corky flecks caused by CRS in Russet Burbank. Photo courtesy of Jim Crosslin, USDA-ARS, Prosser WA

Laboratory testing is performed at Plant Industry Laboratory. We use nucleic acid assays, RT-PCR (reverse transcription polymerase chain reaction). References: D.J. Robinson, Journal or Virological Methods. 1992, 40, ” Detection of tobacco rattle virus by reverse transcription and polymerase chain reaction.” Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Plant Industry Laboratory

We checked all RNA extractions by simultaneously testing for a beta-tubulin reference gene and tobacco rattle virus RNA. References: Mohan Kumar et al., J. Agric. Food Chem. 2007, 55, “Extraction of RNA from Fresh, Frozen, and Lyophilized Tuber and Root Tissues.” Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Plant Industry Laboratory

Survey Results A total of 150 fields in 14 counties tested. 19 Potato producers participated. 50 samples from seed producing fields. 100 from non-seed, fresh vegetable or processing potatoes. All samples tested negative for Tobacco rattle virus, the virus that causes Corky ringspot disease in potatoes. Testing will continue in 2010.

Symptoms of Powdery Scab on Potato Tubers, Spongospora subterranea (Wallr.) Lagerh f.sp. subterranea Tomlinson DATCP Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab A. Phibbs

Common Scab, Streptomyces scabies, a bacterial disease Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab A. Phibbs

Powdery Scab Biology Spongospora subterranea f.sp. subterranea is a soil borne slime fungus (Plasmodiophorales). Swimming spores (zoospores) infect roots, multiply in plant tissue and infect tubers. They form durable resting sporeballs (cystosori) on tuber skin and roots. Cystosori survive in soil for at least 6 years and survive passage thru animal digestive tract. Cystosori release more zoospores, go thru several infection cycles during a growing season. Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab A. Phibbs Powdery scab infects potato, tomato, bell pepper, and Solanaceous weeds: Jimsonweed, groundcherry, nightshade, colt’s foot, wild tabacco and many more. Powdery scab sporeball = cystosori.

Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab Conditions Favoring Disease Cool temperate summers (Soil temperatures of 52  F to 64  F) Alternate periods of wet and dry soil, (Simulated by irrigation) Excess moisture during tuber set. Environmental conditions may be more important than amount of inoculum. Pustules of Powdery scab on Red Norland Potato. A. Phibbs

Spread of Powdery scab Infected seed potatoes Contaminated soil, field to field movement of soil on equipment, tires, boots, … Manure or slurry Spore ball carrying dust in storage Grading lines Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab A. Phibbs

Root Galls Magnified Root Gall Powdery scab symptoms on roots of potato. Powdery scab produces root galls on a resistant potato varieties and re-infect soils. A. Phibbs

Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab Powdery scab on potato “Molli”. A. Phibbs A Brief History of Powdery scab in Wisconsin 2002 UW Clinic’s Brian Hudelson identifies Powdery scab on a Wisconsin potato sample for the first time DATCP conducts a soil survey of 68 fields in 10 counties. 6 fields in Adams, Oconto, Langlade and Waushara counties test positive.

Early Detection PCR detects any life stage of powdery scab (zoospores, plasmodium) in any plant tissue. Examination under microscope and ELISA depend on presence of mature cystosori, formed in the tuber skin or root galls. Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Plant Industry Laboratory A. Phibbs Powdery scab sporeballs or cystosori under magnification. A. Phibbs

Laboratory testing is performed at Plant Industry Laboratory. We use nucleic acid assays, PCR (polymerase chain reaction), Examine tuber skin with microscopes. References: Qu et.al. (Plant Pathology (2001) 50: ). Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Plant Industry Laboratory

Department of Agriculture, Trade and Consumer Protection Distribution of Powdery Scab in Wisconsin* Adams Oconto Pepin Portage Langlade Waushara * at least one field testing positive in a County.

Department of Agriculture, Trade and Consumer Protection Survey Results Total number of potato samples processed in 2009: Potato growers participated in Number of samples testing positive for Powdery scab: 17 (9%). 6 farms tested positive, with a total of 13 fields.

Potato Varieties that tested Positive for Powdery Scab in Wisconsin since 2002: Burbank (no tuber symptoms) Gold Rush (Dark) Red Norland Norkotah MegaChip Molly Ranger Russet Russian Banana Shepody Silverton (no tuber symptoms) Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab Powdery Scab Symptoms on Shepody potato. A. Phibbs

Further Analysis of Powdery Scab DNA sequenced from one sample from each farm that tested positive. All DNA sequences align % with Spongospora subterranea subterranea type II. Two genetically distinct groups (I and II). Reference : Qu, X. & Christ B.J., American J of Potato Research (2004) 81: Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Plant Industry Laboratory

The Problem Affects quality of potatoes (tuber skin blemishes and tumors) Affects crop productivity Affects storability Vectors Potato Mop Top Virus (PMTV) Creates infection opportunities for other diseases: Late blight (Phytophthora infestans) Pink rot (Phytophthora erthroseptica) Dry rot (Fusarium spp.) Black dot (Colletotrichum coccodes) Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Powdery Scab

Phytosanitary Guidelines Diseases of Concern for Exports of Seed Potatoes to Canada and Mexico Viruses Alfalfa Mosaic virus Potato yellow dwarf virus Potato yellowing virus Potato mop top virus (Mexico) Potato spindle tuber viroid PVYn PVYntn Tobacco rattle virus (Mexico) Source: USDA Excerpt 1/25/2010 Nematodes and Diseases Potato Cyst Nematode (Globodera rostochiensis, G. pallida) Columbia Root-Knot Nematode (Meloidogyne chitwoodii) “Tropical” Root Rot Nematode (Meloidogyne javanico) Soybean cyst nematode (Heterodera glycines) Potato Wart (Synchytrium endobioticum) Bacterial ringrot (Clavibacter michiganensis subsp. Sepedonicus Brown Rot (Rastonia solanacearum) race2

Wisconsin Rules ATCP 156, Seed Potato Certification ATCP 21 Plant Inspection and Pest Control ATCP 21.14, Potato rot nematode ATCP 21.14, Late Blight Wisconsin Statues Chapter 93 DATCP Chapter 94 Plant Industry Wisconsin Department of Agriculture, Trade and Consumer Protection Potato Laws and Rules

2010 Survey Testing for TRV and Powdery scab will continue in Please continue to participate! Local contacts for sampling are: Tim Leege (715) and Sara Ott (715) Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey Report 2009 Potato Survey for Corky Ringspot and Powdery Scab Don’t assume your fields are infected, have them tested.

Wisconsin Department of Agriculture, Trade and Consumer Protection Wisconsin Pest Survey / Acknowledgements Kristyn Meyers Rachel Leisso Amanda Nelson Sara Ott Tim Leege Jim Meyer USDA Cooperative Pest Survey Program and Specialty Crop Block Grant Program for funding. For more information: