6Spore (conidia) production of powdery mildew on a grape leaf Severe powdery mildew infection on grape leafSpore (conidia) production of powdery mildew on a grape leafSymptomsPowdery mildew produces white, powdery growth ongrape leaves and shoots.Severely infected leaves may turn brown and fall off.Infected berries appear rusty or scaly.They may fail to mature properly or split open.
7EcologyThe fungus survives the winter in infected grape tissue.Wind carries spores long distances.Unlike most other fungus diseases, powdery mildewtends to be most severe in dry growing seasons.ManagementCultural ManagementLess susceptible to powdery mildew.Plant grapes in full sun with good air circulationFungicides
8Downy Mildew (Plasmopara viticola) Downy mildew on upper side of grape leaf.Appearance of infection on underside of a leafDowny mildew symptoms on a shootDowny mildew symptoms on fruits
9SymptomsInfected leaves develop yellowish-green, and translucent“oily” lesions on their upper surfaces.On lower surfaces, the fungus produces a white to grayishcotton-like growth.Affected leaves eventually turn brown, wither, curl, anddrop early, exposing the immature berries to direct sun.Berries that are infected when young turn light.EcologySpores are spread by splashing rain, wind, and throughThe handling of plants.
10ManagementCultural ManagementWhen planting grapevines, select sunny, open areas withgood air movement.Prune and train vines annually to maintain excellent aircirculationControl tall weeds and grasses in the planting area.FungicidesIf downy mildew is a problem, a program of fungicidesprays may be needed.Captan, Copper compounds, (fixed coppers andBordeaux mixture), Mancozeb, Ridomil/MZ, Ridomil/Copper, Sovran, and Ziram
11Botrytis Bunch Rot of Grape (Botrytis cinerea) Discolored, shriveled berries caused by Botrytis Bunch RotBotrytis cinerea sporulating on grape berries
12SymptomsRipening grapes are affected by a rotWith sufficient rain and humidity, berries split open anddevelop a grayish mold on the surface.Affected berries may shrivel in the dry climate.EcologyInfection is optimal at 15-20oC with free water or over90% humidity. Grape cultivars with dense canopies, thin skins, and/ortight clusters are more susceptible to botrytis bunchrot
13ManagementCultural ManagementPrevent excessive vine growth by judicious use of waterand fertilizer.Prevent berry damage (powdery mildew birds and insects)Canopy managementFungicides
14Phomopsis cane and leaf spot disease (Phomopsis viticola) Infected leaves
16Lesions of Phomopsis cane and leaf spot on shoot and stem
17SYMPTOMSPhomopsis cane and leaf spot appears as tiny darkspots with yellowish margins on leaf blades and veinsBasal leaves with heavy infection become distortedand usually never develop to full sizeOn shoots, small spots with black centers similar tothose found on leaves occur usually on a basal portionof the shootHeavy infection usually results in a scabby appearanceof the basal portions of the shoot
18ControlCultural practicesIncrease air circulation in the vineyardRemoving diseased canes from the vine during normalpruning operationsThis disease can be controlled by applying protectantfungicides before rainy weather beginsChemical controlContact materials such as copper, sulfur, ziram,mancozeb, and maneb
21SymptomsGall formation on the aerial part of the vinesYoung galls are soft, creamy to greenish in color, with nobark or covering.As they age, the tissue darkens to brown.The surface becomes open and the texture becomesmoderately hard and very roughEcologySpread through propagation of diseased wood.
22ManagementCultural ManagementSelect sites with good air and water drainageAvoid vine stress due to poor nutrition or low pHpest control programs for nematodesDo not propagate wood taken from galled vinesHot water treatment of vines is effective in reducing crowngall infection levels in planting materialsFungicides
26DamageSmall holes can be seen on the vineBore the vine and weaken the vascular functionsVine become weak and dryManagementcultural practicessuch as removal and destruction of affected canesChemical practices
27Spider Mite (Tetranychus pacificus) DamageMites feeding on the undersides of the leaves maycause foliage to turn a bronze color.Leaf bronzing early in the season causes stunting andreduces berry quality.ManagementCultural ManagementGood irrigation and fertilizer practices help offsetdamage to foliage.