Grapes A hot, dry climate, well-drained soil and plenty of water is needed to grow grapes. Extended periods of cold weather (below 0 F) will kill vines, yet a period of winter dormancy is needed. Special care should be taken for grapes grown in areas where winter freezes are common. References: Ohio State University, Texas A&M AgriLife Extension. SEASONAL AVAILABILITY ALABAMA ARIZONA CALIFORNIA GEORGIA NEW YORK CANADA CHILE MEXICO References: USDA, Western Growers Association. TYPES, VARIETIES & CUTS Per the U.S. Department of Agriculture (USDA) there are four types of grapes: American, European, Juice, and Muscadine. These four types cover the array of table, wine, juice, and raisin grapes grown. American grapes can tolerate cooler climates and will grow well in the Midwest. European grapes are most typically used for wine making but they can also be used as table, juice, or raisin grapes. These grapes lack cold-hardiness and are better suited to a warmer climate.
GRAPES TYPES, VARIETIES & CUTS CONTINUED Any variety of sweet grapes can be made into grape juice although the most common grape used is Concord. Muscadine grapes, which grow wild in North Carolina and much of the Southeast, are thought to be the first native American grape. Grapes for juice are picked individually and not by the bunch because in many of the varieties, each grape in the cluster ripens at a different time. This can be true for Muscadine grapes as well, which grow in loose clusters with berries falling to the ground when ripe. Some varieties are not recommended for certain regions. For instance, grape varieties such as Jupiter, Saturn, and Sunbelt can be susceptible to Pierce s disease (see below for further information) and should not be grown in areas where the disease has been a significant threat. References: Iowa State University, University of Arkansas Division of Agriculture, USDA. PESTS & DISEASE Common Diseases: Pierce s disease is spread through insects infected by Xylella fastidiosa (bacteria) when they feed on grapevines. Some varieties are tolerant of the disease (for instance, Muscadine) but susceptible varieties will experience vine death as there is no method of treatment. Black rot is spread by dried berries left on the vine or on the ground over winter. Tan spots with tiny black specks appear one to two weeks after infection. To prevent black rot, remove all dried berries from vines before winter. Anthracnose causes round holes in leaves and can be controlled by the same fungicides used to control black rot. Common Pests: Phylloxera is an insect that kills roots of grapevines by laying eggs on rootlets (Muscadines are resistant/tolerant). Grape berry moth larvae feed on blossoms and berries. Insecticides should not be applied until after the grapes have reached the size of small peas or beneficial pollinators will be destroyed. Once the larvae proceeds to the second stage (moth) they are increasingly difficult to control. To prevent hibernation of moth pupae, leaf litter should be cleaned up or buried before winter. Grape leafhoppers feed on the underside of leaves resulting in a stippling look to the affected leaf. Leafhoppers are quite small; they can do serious damage before their presence is known. References: Texas A&M AgriLife Extension, University of Kentucky, USDA. CULTIVATION, STORAGE & PACKAGING Preharvest: Grapes require deep, fertile, well-drained soil on a site with good accessibility, no frost pockets, and few predators. The berries do best when plants are at least 8 feet apart and rows are at least 12 feet apart. Closer rows will have too much shade and compete for water. Vines require proper pruning to produce large clusters and berries, but it is a delicate balance contingent on many factors such as climate, variety, irrigation, weed control, and other forms of vine management. If vines are not properly pruned and allowed to grow unmanaged or if vines are over-pruned, fruit quality will suffer. Sufficient irrigation (one inch per acre per week) and weed control are critical. Grapes require less fertilization than other crops because they adapt so well to a range of soil types. Areas with high rainfall and humidity will require fungicide sprays to keep foliar diseases (discussed below) at bay. Postharvest: Netting over vines and noise makers will help keep birds away from the berries close to harvest time. Birds will start feeding when sugar content reaches 11 to 12%, so it is best to have control measures in place before the grapes become an enticing meal. Harvesting is labor intensive and requires careful planning as timing differs depending on the variety and intended use. A hand refractometer is used to determine sugar levels prior to harvest (usually 15 to 16% for table grapes, 17 to 21% for wine grapes). To harvest table grapes, hold the cluster of grapes by its stem and clip from the cane. Shoots grow upward from the root and are the primary structure of grape vines. The cane is described as a mature, woody shoot. Defective berries should be clipped; pulling defective grapes from the cluster is not recommended as the unattractive leftover stem is susceptible to decay. Juice and wine grapes can be shaken off the vines onto tarps. For larger scale vineyards, a mechanical harvester that
CULTIVATION, STORAGE & PACKAGING CONTINUED GRAPES will rake and shake the berries loose may be recommended. As mentioned previously, Muscadine grapes tend to fall from their clusters when ripe. Placing a basket or tarp underneath the plants and shaking the vine can loosen ripe berries. References: California Rare Fruit Growers, Texas A&M AgriLife Extension, University of Florida/IFAS Extension, University of Kentucky. GOOD ARRIVAL GUIDELINES Generally speaking, the percentage of defects shown on a timely government inspection certificate should not exceed the percentage of allowable defects, provided: (1) transportation conditions were normal; (2) the U.S. Department of Agriculture (USDA) or Canadian Food Inspection Agency (CFIA) inspection was timely; and (3) the entire lot was inspected. AMERICAN U.S. Grade Days Since % of Defects Optimum Standards Shipment Allowed Transit Temp. 10-5-2 5 15-8-4 32-34 4 14-8-4 3 13-7-3 2 12-6-2 1 10-5-2 EUROPEAN U.S. Grade Days Since % of Defects Optimum Standards Shipment Allowed Transit Temp. 12-4-1 5 15-6-3 31 4 14-6-3 3 13-5-2 2 13-5-1 1 12-4-1 Canadian good arrival guidelines (unless otherwise noted) are broken down into five parts as follows: maximum percentage of defects, maximum percentage of permanent defects, maximum percentage for any single permanent defect, maximum percentage for any single condition defect, and maximum for decay. American destination guidelines are 15-10-5-10-4; European destination guidelines are 15-8-8-15-3. References: DRC, PACA, USDA. GRAPES: WEEKLY MOVEMENTS & PRICES, USA Source: Chart by Gallo Torrez Agricultural Price Trends (GTAPT), mgallo@markfinstrat.com, compiled from USDA data.
GRAPES INSPECTOR S INSIGHTS Table Grapes: One of three commodities (kiwifruit and cantaloupes are the other two) that require a minimum percent of soluble solids to meet the U.S. No. 1 grade, the U.S. standard requires the grapes be mature as defined by the agriculture laws and regulations of the state in which produced (to be considered mature, Thompson Seedless and Flame Seedless produced in California must meet a minimum soluble solids reading of 16.5% while Perlettes must meet a minimum 15.5% soluble solids reading) Sound grapes affected by juice of adjoining leaking or decayed grapes are scored as a defect (the defect called wet and sticky berries is considered a free-from defect and its presence, in any amount, will be scored against the tolerance for serious damage); grapes wet from condensation moisture are not scored as a defect Shattered berries are not attached to their capstem and this is considered a defect; reasonable care should be taken when inspecting grapes as all shattered berries (including berries that have fallen off during the normal inspection process) are to be scored as a defect; shattered berries affected by decay will be scored against the decay tolerance. Source: Tom Yawman, International Produce Training, www.ipt.us.com. HEALTH & NUTRITION Grapes are high in Vitamin C, low in sodium, free of fat and cholesterol, and loaded with phytonutrients (plant chemicals) that have been shown to reduce the risks of heart disease and blood clots while improving blood vessel function and lowering blood pressure. Resveratrol is a chemical in Muscadine grapes that provides protection from pests and diseases. It is also present in red wine and is believed to help prevent heart disease. Not a wine drinker? Try jams or juice made from Muscadines two ounces of unfiltered Muscadine juice is equal to the resveratrol in four ounces of red wine. References: Produce for Better Health Foundation, USDA, Western Growers Association. MISCELLANEOUS Raisins are dried grapes; seedless, sweet varieties make the best raisins for eating right out of the container while seeded grapes are most often used in baking. The most widely used method of harvesting raisin grapes is by hand: workers clip bunches from vines, placing them on paper trays between rows to dry in the sun. Growers decide if their grapes will be purposed for wine, raisins, or the table depending most frequently on price. References: Internal Revenue Service Farmers Audit Technique Guide, University of California Cooperative Extension.