Disease Management in Peanuts Barbara Shew Plant Pathology Research and Extension David Jordan Peanut Agronomist NC State University
Major Diseases in Peanut Cylindrocladium black rot (CBR) Tomato spotted wilt tospovirus (TSWV) Sclerotinia Blight Southern stem rot Rhizoctonia limb rot Early and late leaf spot Web blotch
Disease Management
Early leaf spot Late leaf spot
Sclerotinia Blight
Southern Stem Rot or White Mold
Web Blotch
Parathecia or fruiting bodies CBR or Black Root Rot
Botrytis Consider digging early at 25% leaf defoliation
Tomato spotted wilt
Aspergillus flavus possible aflatoxin
General Conditions for Disease Development and Time of Year Disease Weather conditions Time of year Early leaf spot Moist and warm June-September Late leaf spot Cool and moist September Sclerotinia Blight Cool and moist Late July-September CBR (Black toot rot) Cool and moist at planting April and May infection; symptoms appear in August- September Southern stem rot Warm and moist July-August Crown rot Warm and dry May-June Aflatoxin Hot and dry August-September Tomato spotted wilt Dependent on thrips population Most infection in May and early June, some infection throughout the season Web blotch Cool and moist July-September, primarily August and September
Components of Disease Management Crop Rotation Cultivar Resistance Sanitation Disease Scouting and Weather Forecasting Fungicides and Fumigants
Virginia Varieties TSWV Early Leaf spot Sclerotinia Blight Stem Rot Pod Rot CBR Web blotch NC 7 S MR VS S S VS NC 9 VS VS VS S S MR NC 10 C S MR VS MR S MR NC V-11 MR S VS S S S VS NC 12C S MR VS S S MR S-MR Perry VS S S-MR S S MR MR VA-C92R S-MR S S-MR S S S S-MR VA 93B -- VS MR VS S VS VA 98R S-MR S S-MR S S S S Gregory MR S VS S S S MR VC 2 MR S MR S-MR Wilson S-MR S S-MR S S S S-MR MR = moderate resistance, S = susceptible, VS = very susceptible
Tomato spotted wilt
Disease Management Strategies
Seed Transmission of Disease CBR can be transmitted by seed No direct evidence that other major diseases are transmitted by seed
Management of CBR Seed Transmission Maintain accurate records of field history and maps of CBR incidence Adopt 3-year rotation of non-host crops Select fields with low levels of CBR Effectively fumigate Inspect fields at the end of the season Selectively harvest areas of field without CBR Avoid harvesting seed peanuts where CBR exceeds 5%
Importance of Distinguishing Between CBR and TSWV Fumigation reduces CBR but does not affect TSWV (fumigant could be wasted or not applied when really needed). Rotation affects CBR but not TSWV. Perry is resistant to CBR but susceptible to TSWV. NC-V 11 and Gregory are moderately resistant to TSWV but susceptible to CBR. Seeding rate, row pattern, tillage, and insecticide choice affect TSWV but have minimal effects on CBR.
Managing Tomato Spotted Wilt Virus Integrated Pest Management Approach
Symptoms TSWV CBR Rings on leaves Sometimes No Twisted yellowing petioles Usually No Root rot Sometimes Yes Overall yellowing Sometimes Yes Dead terminals Sometimes No Red fruiting bodies No Sometimes Stunted seeds, limbs, whole plant Sometimes No Red seeds Sometimes No Scattered in field Yes Sometimes Clumped in low areas No Often Clearest symptoms Early to midseason Late season Cracked seed coats Yes No Cinnamon speckles on seed No Yes
Cylindrocladium Black Rot (CBR) Vapam HL 42% @ 7.5 gallons Metam 42% @ 7.5 gallons
Seed Treatments Captan + PCNB + Etridiazole Apron + Terraclor Thiram + PCNB + SP Extender Thiram + PCNB + Vitavax + SP Ext. Vitavax 300 (Captan + Carboxin) Vitavax PC (Captan + PCNB + Vitavax) Vitavax Captan + Maneb
Nematode Control Temik 15G Nemacure 15G Telone II Vapam HL 42% Metam 42%
Cercospera Leaf Spot Benlate Topsin + Manzate Dithane Penncozeb Dithane F45
Southern Stem Rot and Rhizoctonia Limb and Pod Rot Folicur Moncut Abound Headline
Sclerotinia Blight Rovral 4L Omega 500 Endura Contans
Cercospera Leaf Spot Chlorothalonil (mulitple products) Dithane, Manzate, Mankocide, Kocide Tilt, Tilt/Bravo Stratego Folicur Abound Headline
Web Blotch Chlorothalonil Folicur Abound Headline
Disease Management Typical Grower Program Considerable variation in spray programs Seed treatments (fungicides) Metam sodium (soil fumigant for CBR) Chlorothalonil (several brands) (1X) Tebuconazole (Folicur, 2 to 4X) OR azoxystrobin (Abound, 2X) OR pyraclostrobin (Headline, 1 to 2X) OR flutolanil (Artisan, 1X depending on rate) Chlorothalonil (several brands) (1 to 2X) Fluazinam (Omega 500, 1 to 2X) OR boscalid (Endura, 1 to 2X)
Restrictions on Feeding Fungicide- Treated Vines to Livestock Do Not Feed Vitavax Benlate Abound Rovral Omega 500 See Label Restrictions Folicur Moncut Tilt Chlorothalonil Headline
Benefits of Using Weather-Based Advisories Prevent unnecessary fungicide sprays Increase precision of necessary sprays Leaf spot and Sclerotinia Blight Advisories are available and are effective. The leaf spot advisory works relatively well for southern stem rot and rhizoctonia limb and pod rot. Advisories do not work for web blotch
Disease Epidemics, Weather-Based Advisories, and Fungicides Presence of pathogen Favorable temperature and humidity Epidemics can occur if temperature and relative humidity are favorable for extended periods of time Fungicides can be applied more precisely if predictions of epidemics are accurate Fungicide applications can be avoided if conditions are not favorable for disease development Reducing fungicide applications can have positive ramifications on environmental impact, secondary pest outbreaks, and profit When fungicides are needed they are generally very cost effective Some varieties and management situations are less forgiving if fungicides are not applied on time
Fungicide Type Resistanc e risk Coppers (various) Chlorothalonil (various) Broad spectrum Broad spectrum Very low Very low Tebuconazole (Folicur) DMI Moderate to high Propiconazole + chlorothalonil (various) Flutalonil + propiconazole (Artisan) Propiconazole + trifuloxystrobin (Stratego) DMI + broad spectrum Oxathiin + DMI DMI + STAR Low in mix Low in mix Low in mix Alternate with: All All Coppers, cholorothalonil, azoxystrobin, pyraclostrobin, boscalid Coppers, chlorothalonil, azoxystrobin, pyraclostrobin, boscalid Coppers, chlorothalonil, azoxystrobin, pyraclostrobin, boscalid Coppers, chlorothalonil Azoxystrobin (Abound) STAR High Coppers, chlorothalonil, tebuconazole, propiconazole + chlorothalonil, flutalonil + propiconazole, boscalid Pyraclostrobin (Headline) STAR High Coppers, chlorothalonil, tebuconazole, propiconazole + chlorothalonil, flutalonil + propiconazole, boscalid Boscalid (Endura) Carboxamide High All