Disease management in organic grape production Annemiek Schilder Michigan State University East Lansing, Michigan

"Organic agriculture is an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony." Organic Trade Association

" Organic food is produced according to certain legally regulated standards. For crops, it means they are grown without the use of conventional (synthetic) pesticides, artificial fertilizers or sewage sludges. Also, at all levels, organic food is produced without the use of genetically modified organisms. " Wikipedia

Regulations for crop production and handling provided by the USDA National Organic Program Farms must be certified by accredited certifying agent based on farm plan and on-site inspection 3-year transition period before food can be labeled as organic Exempt from certification if sales < $5,000/year

List of products approved for use in organic crop production: Organic Materials Review Institute

Important grape diseases in the Midwest Downy mildew (Plasmopara viticola) Powdery mildew (Uncinula necator) Phomopsis cane and leaf spot (Phomopsis viticola) Botrytis bunch rot (Botrytis cinerea) Black rot (Guignardia bidwellii) Crown gall (Agrobacterium tumefaciens) Virus diseases (TRSV, ToRSV, GLRaV)

Non-chemical disease management options Select resistant or less susceptible varieties Select a suitable site with good airflow and drainage Prune and train vines to reduce canopy density Leaf removal to decrease humidity and increase sunlight penetration (especially for bunch rot) Prune out and remove diseased plant parts Clean planting material from reputable nursery Minimize plant stress and injury

Organic fungicide options for grapes 1) Copper, sulfur, lime sulfur (not all formulations) 2) Potassium bicarbonate salts (Armicarb, Kaligreen, Milstop) 3) JMS Stylet Oil (paraffinic oil) 4) GantecGold (neem oil) 5) Sporan (thyme oil, rosemary oil, clove oil) 6) Serenade (Bacillus subtilis – biocontrol agent) 7) Sonata (Bacillus pumilis – biocontrol agent) 8) OxiDate (hydrogen peroxide) 9) Regalia (giant knotweek extract) 10) Blightban (Pseudomonas fluorescens) All of these are contact materials/protectants

Powdery mildew (Uncinula necator)

Powdery mildew severity % Total leaf area infected Vidal, 2000 a d bc b d Ampelomyces quisqualis c

Evaluation of organic fungicides for powdery mildew control /4/99 8/11/99 8/18/99 8/25/99 9/1/99 Control Armicarb Armicarb/Oil Stylet oil Nova % Leaf area affected Foch, 1999, Sutton’s Bay

Efficacy of organic fungicides for control of powdery mildew in ‘Niagara’ grapes, Fennville, MI, 2009 % Leaf area infected a ab bc c c cd d d d

Efficacy of organic fungicides for control of powdery mildew in ‘Niagara’ grapes, Fennville, 2009 % Leaf area infected a bc b b c c c c c c All treatments: + NuFilm

Efficacy of different fungicide programs in controlling powdery mildew on leaves of ‘Chancellor’ grapes, Fennville, a % Leaf area infected b b c c

Downy mildew (Plasmopara viticola)

% Leaf area diseased Downy mildew severity b c a Vignoles, 2001

% Leaf area diseased Downy mildew severity b c a Niagara, 2002

Efficacy of organic fungicides for control of downy mildew in ‘Niagara’ grapes, TNRC, Fennville, a % Leaf area infected b b bc c c c d d e e

Efficacy of different fungicide programs in controlling downy mildew on leaves of ‘Chancellor’ grapes, TNRC, Fennville, a % Leaf area infected b b c c

Efficacy of organic fungicides for control of downy mildew in ‘Niagara’ grapes, Fennville, 2009 % Leaf area infected a b d c cd bc d d e

Efficacy of organic fungicides for control of downy mildew in ‘Niagara’ grapes, Fennville, 2009 % Leaf area infected a b c bc d c c c c c

Botrytis bunch rot (Botrytis cinerea)

Botrytis bunch rot severity % All berries infected Vignoles, 2000 ab bc a cd d

Botrytis bunch rot severity % All berries infected Aurore, 2001 a a a b

Black rot (Guignardia bidwellii)

Black rot severity % All berries infected with black rot Vidal, 2000 a b b b

Black rot severity % Berries with black rot symptoms Concord, 2001

Efficacy of organic fungicides for control of black rot in ‘Niagara’ grapes, TNRC, Fennville, a % Berries infected ghijk k abc hijk ghij fghi efgh defg def cde bcd

Phomopsis cane and leaf spot (Phomopsis viticola)

Phomopsis rachis lesion severity % Total rachis area infected Vidal, 2000 a c c b b

Phomopsis fruit rot severity % All berries infected Vidal, 2000 a d cd bc c

% Rachis infection Efficacy of organic fungicides for control of Phomopsis in ‘Niagara’ grapes, TNRC, Fennville, 2009 a b b bc c c c cc c c c c

Dormant sprays (copper, sulfur, lime sulfur) Not all products OMRI-listed

% Rachis area infected a b b b b Approximate product cost per acre: $5 $65 $6 $73 b $20 Vignoles, 2004 Effect of single dormant sprays on Phomopsis

Effect of OMRI-listed dormant sprays on Phomopsis % Berries infected Niagara, 2006 a b c c

Effect of single dormant sprays on black rot % Berries infected b Niagara, 2004 a a ab b c

Effect of single dormant sprays on powdery mildew Number of berries infected Chardonnel, 2005 a b b

Conclusions  Disease control in organic vineyards is possible, but there are fewer fungicide options than in conventional production and these are generally not as effective as the best conventional fungicides – therefore they may need to be applied more often  All products are protectants: need to be applied before infection and are susceptible to wash-off by rain  Promising products: Serenade, Sonata, Stylet Oil, Armicarb, Kaligreen

 Organic growers need to rely more on site selection, resistant cultivars, canopy management to reduce humidity and increase sunlight penetration, and pruning to remove diseased plant parts Conclusions  Dormant sprays are a good option (before budbreak) to reduce overwintering inoculum  NuFilm (or similar sticker/extender) should be used

 A good resource for organic grape production is ATTRA (  Other useful resources: - Grape IPM Pocket Scouting Guide - Midwest Small Fruit and Grape Spray Guide - MSU Fruit Management Guide (E-154) - MSU Grape website: Conclusions