Late Blight: being prepared for 2010 NOFA winter Conference January 2010 R. Hazzard, UMass Extension www.umassvegetable.org What happened in 2009? 1. IDEAL WEATHER – Rain – - 7 solid weeks (June & July, early August) – Cool, cloudy conditions; long leaf wetness Photos courtesy of Jim Dill, U Maine Photos courtesy of Tom Zitter & Meg McGrath, Cornell Univ. Photos courtesy of Tom Zitter & Meg McGrath, Cornell Univ. What happened in 2009? 2. Inoculum spread throughout New England – Bonnie Plants starts plugs in Alabama, ships north – One greenhouse/state grows plants on – Big box stores sell plants to home gardeners. Photos courtesy of Jim Dill, U Maine Rapid spread • June 16-18 – late blight reported PA, NJ • June 25 – late blight reported Geneva NY big box store • June 25-26- late blight found in big box stores in ME, CT, MA, NH • June 26 – alerts sent to growers • July 10- 13 –confirmed infected field tomatoes in CT and MA ---„snowball‟ • July 14-21- confirmed in 5 counties in MA Sporangia dispersal Survive in cool, cloudy Travel on wind Move for miles 70-80 F ideal Infections produce millions more spores How fast can late blight kill crops ? July 23 July 30 Mating Type A-1 A-2 Oospore (survives winter) New US – 8 (earlier years) England US - 14/17 - 2009 Strains – Sporangiophore A2 Zoospore (flagellated) What about 2010? • Late blight pathogen can only survive on living tissue • Infected potato tubers are the key, most likely source – In storage – Left in ground, below frost line – Compost pile Late blight infected tuber Goal # 1: no late blight inoculum! • Destroy/kill infected potatoes (culls) – Freeze & thaw on surface – Bury deep – Feed to livestock • Purchase certified disease-free potato seed – 1% tolerance • Scout last year‟s fields, compost piles, for volunteer potatoes; destroy promptly. • Rotate potato and tomato to new fields Goal # 1: no late blight inoculum! • Tomato greenhouse from 2009? – let it freeze! • Grow your own tomato starts from seed • If you purchase bought-in transplants, isolate for 1 week & watch for symptoms • Visit big box stores in May – scout their plants – report if diseased Resistant /tolerant varieties Tomatoes – „Legend‟ tomato from Oregon (Territorial Seed Co). – NC breeding program: Mountain Magic, Plum Regal (Bejo Seeds – Johnny‟s) – „Juliet‟, „Stupice‟, 'NC 03220' (Org. Seed Alliance, WA) – Others: Matt‟s Wild, Ferline, Fantasio Potatoes Kennebec, Sebago, Allegany, and Chieftain Cultural practices • Rotate potato and tomato crops to new fields • Trickle irrigation (not overhead) • Stake and weave with moderate pruning for drier leaves Early blight Septoria leaf spot The „other blights‟…come every year • Septoria survives in crop debris • Early blight & Septoria move up the plant, reduce yield Early blight Grow greenhouse or hoophouse tomatoes • Heat and vent in evening to reduce leaf wetness overnight – Will help with Botrytis, Fulvia leaf mold, Late blight Know the late blight risk in your area • Listen to reports about late blight UMass Vegetable Notes (MA) • www.umassvegetable.org • Subscribe to Email list (free!) • Report / get diagnosis of suspected LB • Weather conditions – 18 „severity units‟ accumluate Use protective fungicides if Late blight risk is high -late blight is present within 40 miles -weather conditions have been/are favorable wet, cool, cloudy Blitecast >18 severity points -take action to protect the crop – before infection. Organic products with late blight on label Stimulate plant resistance: Serenade ASO (Bacillus subtilis) 6 qts/A Serenade MAX (Bacillus subtilis) 1-3 lb/A Sonata (Bacillus pumilis) 2-6 qts/A Kill spores (no residual) Oxidate (hydrogen dioxide) 40-128 fl oz/100 gal Prevent spore germination (increase resistance?) Copper fungicides Mode of action?? Sporan EC (rosemary, clove, thyme oils) 1-3 pints/A Sporatec (rosemary, clove, thyme oils) 1-3 pints/A “Copper is an essential nutrient for plant growth and disease resistance, although direct toxicity was long thought to be the mechanism responsible for disease control with copper. Fertilizer and pesticide applications containing Cu can provide effective control of many diseases by stimulating plant disease mechanisms. This aspect of the effect of Cu is frequently overlooked.” “Mineral Nutrition and Plant Disease”, L Datnoff, W. Elmer, D. Hubner. 2008 Another good reference: • “Handbook of Plant Nutrition‟, A. Barker & D Pilbeam, 2007 Considerations in copper management • Copper is essential micronutrient for plants, animals and humans. • Interaction with organic matter, manure, pH, other minerals is complex. • Copper rapidly forms organic complexes, binds to humus, does not leach • Deficiency is more common than excess in NE soils What about Copper Soil Toxicity? • Typical level, UMass Soils Lab samples = 0.2 to 0.3 ppm • Toxicity to plants occurs at 30-60 ppm – Vineyards, orchards after years of use • 2 lb/acre copper fungicide adds estimated 0.5 to 1.0 ppm in soil • 2 organic fields tested after sprays every 5-7 days= 0.3, 0.8 ppm - needs more study OMRI Listed Copper Fungicides • Champ WG • Nu Cop® 50 WP *registered in NY,Massachusetts, & other New England states If you sell your crop, use one of these Home garden: look for any copper hydroxide or copper sulfate product Using copper: Rates of application for NuCop 50WP Potato: 1.5 to 4 lb/acre Tomato: 2-3 lb/acre 3 lb/acre = 1.1 oz/1,000 sq ft. apply at 7-10 day intervals, more frequently when disease is severe Note: Champ WG may be used in greenhouse What about personal safety? • Read and follow the label • What you need to wear when using copper: – Eye protection (goggles) – Long sleeved shirt and pants – Shoes and socks – Chemical resistant gloves • Don‟t work in the crop for 24 h • May be applied up to 24 hr before harvest – Pickers should be careful not to rub their eyes if handling fruit with residue.