Avocados The avocado is thought to have originated in Southern Mexico, but the fruit was cultivated from the Rio Grande down to central Peru before the Europeans arrived in the New World. The fruit grows on trees that can reach 60 feet or higher, but typically stand about 30 feet tall. Most varieties are pear-shaped and can range in skin color from yellow-green to green to a dark purple that is almost black in appearance. Skin texture ranges from smooth to bumpy while the flesh of the fruit is typically a buttery yellow or yellow-greenish color depending on variety. In the middle sits a single seed, from 2 to 2.5 inches long, which can vary in shape but is usually hard and heavy with ivory coloring beneath papery-thin brown seedcoats. References: Agricultural Marketing Resource Center, Purdue University, University of California. SEASONAL AVAILABILITY CALIFORNIA FLORIDA HAWAII BRAZIL CHILE DOMINICAN REPUBLIC MEXICO NEW ZEALAND PERU References: California Avocado Commission, Florida Department of Agriculture, USDA.
TYPES, VARIETIES & CUTS There are three main types of avocados: West Indian, Guatemalan, and Mexican. West Indian varieties have leathery, pliable, nongranular skin and low oil content in the flesh. The skin of Guatemalan varieties ranges from thin to very thick, and is granular. Mexican varieties have high oil content (up to 30%) with thin and tender skin. These varieties are more cold resistant than others or hybrids, but are the least salt tolerant. The least cold tolerant are West Indian types, yet they have a high salt tolerance. Salt tolerance is important as soil salinity can reduce fruit yields. Popular hybrids include Guatemalan-West Indian and Guatemalan-Mexican. Pure Guatemalan avocados are not conducive to Florida growing conditions, but Guatemalan-West Indian hybrids thrive in the state. Hass avocados are perhaps the most recognizable variety of the Guatemalan-Mexican hybrids. References: Purdue University, Texas A&M University. AVOCADOS PESTS & DISEASE Common Diseases: Anthracnose is recognized by unhealthy or dead leaves, but can affect the flowers, fruit, and twigs as well. Yellow spots on leaves will turn brown before spreading to the whole leaf. Trees may drop leaves prematurely if disease is severe. Affected fruit will have small sunken areas with lesions becoming darker and larger after harvest. Bacterial canker is noticeable on the bark as slightly sunken, dark areas. White powder forms around or over the lesion which is left behind after fluid oozing from the area dries. Scab produces spots that become sunken in their center as fruit matures. Lesions on leaves are less noticeable, as they are more common closer to the upper canopy than the lower branches. Spots start out small but increase in size until the center drops out. Common Pests: Western avocado leafroller is a caterpillar that causes severe damage by consuming the tree s leaves and feeding on the fruit itself. Avocado thrips lay their eggs on the underside of leaves and feed on the fruit, damaging the skin. Thrips also feed on the leaves, producing scars and a bronzed hue. The omnivorous looper also feeds on leaves; healthy trees can usually tolerate the damage but extensive leaf loss can cause sunburn and affect yields the following year. Most damage occurs when loopers eat the fruit, which causes the skin to scar and become misshapen. References: UC Davis Integrated Pest Management, University of Florida/IFAS Extension. CULTIVATION, STORAGE & PACKAGING Preharvest: West Indian avocados are most suited to a tropical climate with high humidity such as southern Florida. Guatemalan avocados are successful in warm climates with less humidity, such as the California coast. Mexican avocados are the hardiest of the three and most prominent in California, able to handle temperatures as low as 25 F (-4 C) but do not respond well in tropical climates. Windbreaks are necessary in areas of strong winds as it reduces humidity, dehydrating flowers and causing fruits to fall prematurely. Despite its many prerequisites for climate, the avocado tree does well in most any type of soil, but good drainage is required. Trees should be spaced 25 feet to 35 feet apart depending on soil type. Branches will die back if touching another tree. Upper soil should stay moist and fertilizing must wait until after blooming when the fruit is firmly set. As mentioned previously, avocado trees can grow up to 60 feet tall or higher; this height is often impractical for commercial growing purposes so many growers cut the trees back to a manageable height (around 16 to 18 feet), allowing them to reach heights of 30 feet again before cutting them back again. Developing avocados are heavy and may require propping up branches to avoid breakage. Postharvest: An inhibitor in the fruit stem prevents avocados from ripening on the tree. It can be presumed that when the fruit starts to fall off the tree it is mature, but reliably determining maturity involves comparing dry weight and oil content in most production areas. In Florida, harvesting is determined by calendar date as these varieties tend to have lower oil content.
AVOCADOS CULTIVATION, STORAGE & PACKAGING CONTINUED Avocados are sensitive to rough handling; as a result, fruit is no longer detached by a forked stick to fall on the ground. For lower fruit, clippers are used, and for those higher up in trees, a long-handled stick with a V-shaped cutter is used to cut the stem. Fruit then falls into a sturdy cloth bag. Workers wear gloves to avoid scratching the fruit, which is then packaged in padded boxes or cartons or molded trays. Optimum temperature for mature green avocados (depending on variety) is 41 to 55 F (5 to 13 C) and 36 to 40 F (2 to 4 C) for ripe fruit with 90 to 95% relative humidity. Avocados produce ethylene after harvest, which increases significantly as they ripen. Treating avocados with ethylene can induce ripening in 3 to 6 days depending on the variety and maturity. Controlled atmospheres will delay softening and reduce ethylene production. References: Purdue University, Texas A&M University, UC Davis Postharvest Technology website. 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. There are no good arrival guidelines for this commodity specific to Canada; U.S. guidelines apply to shipments unless otherwise agreed by contract. References: DRC, PACA, USDA. U.S. Grade Days Since % of Defects Optimum Standards Shipment Allowed Transit Temp. ( F) 10-5-1 5 15-8-3 32 4 14-8-3 3 13-7-2 2 11-6-1 1 10-5-1 AVOCADOS: WEEKLY MOVEMENTS & PRICES, USA Source: Chart by Gallo Torrez Agricultural Price Trends (GTAPT), mgallo@markfinstrat.com, compiled from USDA data.
INSPECTOR S INSIGHTS AVOCADOS Avocados imported into the United States must meet minimum grade requirements prior to importation (i.e., release by U.S. Customs) per the Agricultural Marketing Agreement Act. This means avocados must grade at least U.S. No. 2, in the U.S. Standards for Grades of Florida Avocados. Maturity requirements also apply to avocados other than Hass, Fuerte, Zutano, and Edranol varieties The fungus, anthracnose, is a free from defect of the U.S. No.1 Grade, therefore, if anthracnose is present in any amount it is scored as a defect against the 5% tolerance (i.e., as serious damage); if it penetrates the flesh or when the anthracnose spot is soft, score against the 1% tolerance for decay (i.e., as very serious damage) The fungus cercospora spot is also a free from defect of the U.S. No.1 Grade, but is scored against the 10% tolerance for total defects. Source: Tom Yawman, International Produce Training, www.ipt.us.com.