Grape Vine Fungal Trunk Diseases

Meet “Botryosphaeria” A fungus living in your vines Causes spur, cordon and vine death Was previously unknown here (?) Is spreading world-wide

Botryosphaeria Can be confused with virus, or nutritional deficiencies. Vascular discoloration is typical, including brown/black streaks (necrosis in the xylem tissue)

About Botryosphaeria One of several fungi causing trunk disease Spreads by infection of pruning and other wounds via air-borne spores Spores are produced in wet weather, maybe high humidity Can quickly make vineyards uneconomical because of loss of bud break, and vine deaths May be a cause of low yields in Midwest

Symptoms caused by Trunk Disease Fungi Trunk and cordon Wedge-shape lesions when cut in cross-section (Eutypa) Dieback described as ‘dead arm’ and loss of spur positions Shoots Stunted appearance during the spring Bud burst Delayed or lack of growth in one or more spur positions Canes Bleached Buds Necrotic

Fungal Disease Management Late pruning Prune as late as possible before bud break Double pruning First pass is done in the winter Prune to two buds in early spring before bud break Fungicide treatments and wound protection (VitiSeal, B-Lock, Topsin M, etc.)

Fungal Disease Management Remedial surgery and sucker training Vine training Cane pruning Reduces disease severity Spur/cordon pruned Disease levels may increase Avoid large cuts during pruning Vine debris MUST be removed from site

But it can be controlled Protect all pruning wounds by painting/spraying fungicides/paint mixtures as are used in CA At first symptoms in vineyard, begin saving trunk shoots, as low as possible Train up 1-2 new trunks, remove old cordons and trunks Remove pruning debris (a good practice for many problems, e.g. grape cane borer, other pests, disease inocula)

Avoid stress that can weaken vines Correct planting, irrigation, fertilization Avoid early fruit production/harvest Avoid stress that can weaken vines

Life Cycle of Botryosphaeria pycnidia conidia over winters on diseased wood pseudothecia prevent new infection ascospores on cankers Break Disease Cycle rain splash and wind spread conidia and ascospores remove inoculum source canker fresh wound around initial infection point wood necrosis vascular system damaged by fungal growth conidia germinate and invade woody tissue via xylem dead arm, vine death Life cycle of botryosphaeria dieback in grapevines showing the key points for management options to break the disease cycle.

Cultivar Avg. Disease Intensity Petite Pearl 2.75 Sabrevois 3.10 Brianna 3.30 Frontenac Blanc 3.45 Frontenac Gris 3.50 Lemberger 3.60 Norton 3.62 La Crescent 4.00 Aromella 4.10 Chambourcin 4.88 Cayuga White 4.96 Noiret 5.60 St Croix 5.62 Chardonel 5.73 Vidal Blanc 5.75 Lacrosse 5.76 Bianca 6.00 Grafted Chambourcin 6.20 Frontenac 6.33 Edelweiss 6.40 Niagara DeChaunac * Leon Millot 6.66 Vignoles 6.80 Corot Noir 7.60 Traminette 8.10 * Known that it is very susceptible but was not in our evaluation

Don’t ignore Trunk Diseases DO NOT PANIC!!!! Learn to recognize symptoms TREAT EARLY You will be rewarded with old, healthy vineyards Read “Don’t let trunk diseases ruin your day, and your vineyard” The Grapevine, May June 2018