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Root Crops – Diseases Midwest Veg Guide 2022 257 organic matter. The total amount of N from fertilizer (including starter) and other credits should be 50 (radish), 90 (turnip), 100 (beets, fresh market carrots, horseradish, parsnip, rutabaga), 120 (processing carrots), or 150 (celeriac) pounds N per acre on mineral soils, and 50 pounds less on muck soils. Root Crops – Diseases Reviewed by Dan Egel – Sept 2021 Recommended Controls Aster Yellows (Purple-Top Wilt) of Multiple Crops - Phytoplasma Mollicutes This pathogen is transmitted by leafhoppers. Infection rates can jump when adjacent crops are harvested mid-season, such as alfalfa or wheat. Non-Pesticide Beet, Carrot, Celeriac, Parsnip, Radish, Rutabaga, Turnip | Use disease-free seed. Hot water seed treatment may reduce this seedborne disease. Use temperatures and times of 122 F for 20 minutes for carrot, rutabaga and turnip, 122 F for 15 minutes for radish, or 118 F for 30 minutes for celeriac. Prompt destruction of the finished crop with tillage to rapidly breakdown tissue is an important method to prevent disease build-up. Destroying perennial weed hosts near high-value crops can reduce inoculum that is transmitted by leafhoppers. Pesticide Insecticides Beet, Carrot, Celeriac, Parsnip | Use an insecticide to control leafhoppers that transmit the disease. Leafhoppers must be controlled before they feed. See Insect section. Brittle Root of Horseradish - Spiroplasma Bacteria This pathogen is transmitted by leafhoppers. The symptoms include inward curling and yellowing of leaves, stunting of new growth, and an eventual collapse of the foliar portion of the plant. Root tissue becomes tan to black and they become easy to snap off. Pesticide Insecticides Horseradish | For TuMV: maintain an aphid management program. See Insects section. For Brittle Root: maintain a leafhopper management program. See Insects section. Cavity Spot of Carrots - Pythium Oomycete Cavity spot can affect root quality and yield. Pesticide Presidio (4SC) (fluopicolide) Carrot | 4 fl. oz. per acre. Labeled for in-furrow applications. Use 5-10 gallons of water per acre. REI: 12-hour. PHI: 7-day FRAC 43. Ranman 400SC (34.5) (cyazofamid) Carrot | 6 fl. oz. per acre. REI: 12-hour. PHI: 14-day. FRAC 21. Reason 500SC (4.13) (fenamidone) Carrot | 8.2 fl. oz. per acre. REI: 12-hour. PHI: 14-day. FRAC 11. Ridomil Gold Bravo SC (mefenoxam, chlorothalonil) Carrot | 1.5-2.5 pts. per acre. REI: 48-hour. PHI: 7-day. FRAC 04, FRAC M05. Ridomil Gold SL (4SC) (mefenoxam) Carrot | 0.25-1.3 pt. per acre Begin applications 28 days after planting as broadcast sprays, or 40 days after planting for banded sprays. Do not exceed 2.8 pts. per acre per season. Other formulations include MetaStar, Subdue Maxx, Ultra Flourish, and Xyler. Rates vary by formulation. REI: 48-hour. PHI: 7- day. FRAC 04. Damping-Off Seed and Seedling Rots of Multiple Crops - Multiple Pathogens Non-Pesticide Beet, Carrot, Celeriac, Horseradish, Parsnip, Radish, Rutabaga, Turnip | Avoid excess moisture to young plants by monitoring irrigation frequency. Plant in warm field soils. The fungi responsible for damping-off in field soils cause more loss when the seedling is slow to emerge. Pesticide azoxystrobin products (azoxystrobin) Beet, Carrot, Celeriac, Horseradish, Parsnip, Radish, Rutabaga, Turnip | Rates vary widely depending on crop and application method. REI: 4-hour. PHI: 0-day. FRAC 11. Presidio (4SC) (fluopicolide) Beet, Carrot, Celeriac, Horseradish, Parsnip, Radish, Rutabaga, Turnip | 3-4 fl. oz. per acre. Pythium damping-off only. REI: 12-hour. PHI: 7- day. FRAC 43.