The Avocado 1 DESCRIPTION. Circular J. H. Crane, C.F. Balerdi, and C.W. Campbell 2. Tree

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1 Circular 1034 The Avocado 1 J. H. Crane, C.F. Balerdi, and C.W. Campll 2 Scientific Name: Persea americana Miller Common Names: avocado, avocado-pear, aguacate (Spanish) Family: Lauraceae Origin: Avocados are indigenous to tropical America. Three ecological races Mexican, Guatemalan, and West Indian are recognized. Distribution: Avocados are grown in tropical and subtropical areas of the world. In Florida, commercial production is primarily in Dade and Collier Counties, however, small plantings and isolated trees are found in warm locations throughout the state (Figure 1). History: Avocados have en cultivated in tropical America since pre-columbian times. The first recorded importation into Florida was in 1833 and into California in Importance: One of the important fruits in the American tropics, the avocado is grown commercially in many areas of the world including Mexico, Brazil, Australia, Israel, Chile, tropical Africa, California, and Florida. Tree DESCRIPTION A medium (30 ft; 9.1 m) to large (65 ft; 19.8 m) tree, the avocado tree is classified as an evergreen, although some varieties lose their leaves for a short time fore flowering. The tree canopy ranges from low, dense and symmetrical to upright and asymmetrical. Limbs are easily broken by strong winds or heavy crop loads. Figure 1. Avocados can grown in these lower western and eastern coastal regions of southern Florida (indicated by solid black shading). 1. This document is Circular 1034, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published as FC-3: March Most recent revision:. Please visit the FAIRS Web site at 2. J. H. Crane, Associate Professor and Tropical Fruit Crops Extension Specialist, Tropical Research and Education Center, Homestead, FL; C.F. Balerdi, Multi- County Fruit Crops Extension Agent III, Dade County, Homestead, FL; C.W. Campll, Emeritus Professor, Tropical Research and Education Center, Homestead, FL; Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Waddill, Dean

2 The Avocado Page 2 Leaves Leaves are 3 to 16 inches (7.6 to 40.1 cm) in length and variable in shape (elliptic, oval, lanceolate). They are often puscent and reddish when young, then come smooth, leathery, and dark green when mature. Inflorescence The many-flowered lateral inflorescences (structures that hold the flowers) are borne in a psuedoterminal position. The central axis of the inflorescence terminates in a shoot. Flowers are perfect, yellowish-green, and 3/8 to 1/2 inch (1 to 1.3 cm) in diameter. Fruit The fruit is a rry, consisting of a single large seed, surrounded by a buttery pulp. Fruit contain 3 to 30% oil (Florida varieties range from 3 to 15% oil). The skin is variable in thickness and texture. Fruit color at maturity is green, black, purple or reddish, depending on variety. Fruit shape ranges from spherical to pyriform, and the fruit weigh from a few ounces to 5 lbs (2.3 kg). The fruit does not generally ripen until it falls or is picked from the tree. In Florida, the fruit is considered sufficiently mature for harvest when it reaches a specified calendar date and weight or size. The specific dates, weights, and sizes used to determine maturity vary by variety. An alternative method in some places (e.g., California) has en to harvest when the fruit contain a specified minimum oil content and/or dry matter content. However, this method has not proved useful for the varieties of avocados grown in Florida. See Plate 1. Table 1. Behavior of a Type A and Type B avocado flower. Type A 1st Day A.M. Flower opens, stigma receptive Type B P.M. Flower closed Flower opens, stigma receptive Night Flower closed Flower closed 2nd Day A.M. Flower closed Flower opens again, pollen shedding Pollination P.M. Flower opens again, pollen shedding Varieties are classified into A and B types according to the time of day when the female and male flower parts come reproductively functional (Table 1). New evidence indicates avocado flowers may both self- and cross-pollinated under Florida conditions. Self-pollination occurs during the second flower opening when pollen is transferred to the stigma. Cross-pollination may occur when female and male flowers from A and B type varieties open simultaneously. Self-pollination appears to primarily caused by wind, whereas cross-pollination is caused by large flying insects such as es and wasps. Varieties vary in the degree of self- or cross-pollination necessary for fruit set. Some varieties, such as 'Waldin', 'Lula', and 'Taylor' fruit well in solid plantings. Others, such as 'Pollock' and 'Booth 8' (both B types) do not, and it is probably advantageous to plant them in rows alternating with other varieties (A types) which bloom simultaneously to facilitate adequate pollination. VARIETIES Avocado varieties are classified in three groups, known as the West Indian, Guatemalan and Mexican races, with distinguishing characteristics summarized in Table 2. Plate 1. Avocado fruit ('Simmonds' variety).

3 The Avocado Page 3 Table 2. Characteristics of West Indian, Guatemalan, and Mexican races of avocados Z. Characteristics West Indian Guatemalan Mexican Origin Tropical lowlands Tropical highlands Tropical highlands Foliage No odor No odor Anise-scented Blooming season February to March March to April January to February Maturity season May to Septemr Septemr to January June to Octor Development period 5 to 8 months 10 to 15 months 6 to 8 months (fruit set to maturity) Fruit size 1 to 5 lbs ½ to 5 lbs Not over 1 lb (0.5 to 2.3 kg) (0.2 to 2.3 kg) (Not over 0.5 kg) Skin texture Leathery-smooth Woody-rough Papery-smooth Fruit oil content Low Medium to High Medium to High Cold hardiness Young trees 28 to 30F 26 to 28F 24 to 26F (-2 to -1C) (-3 to -2C) (-4 to -3C) Mature trees 25 to 30F 21 to 25F 18 to 25F (-4 to -1C) (-6 to -4C) (-8 to -4C) Z Tree response to freezing temperatures is influenced by tree health, stage of growth, and cultural practices. Race Early varieties are usually of West Indian and Mexican origin, whereas midseason and late varieties are hybrids tween the races and have intermediate characters. Some characteristics of Florida avocado varieties are summarized in Table 3. CLIMATE West Indian and some hybrid varieties are st adapted to a lowland tropical climate and relatively frost-free areas of the subtropics. Mexican varieties are more cold-tolerant and not well-adapted to lowland tropical conditions. Guatemalan x Mexican hybrids are generally more cold-tolerant than West Indian x Guatemalan hybrid varieties. Some of the more cold-tolerant varieties in Florida include: Brogdon, Gainesville, Mexicola, and Winter Mexican. However, it may difficult to find plants of these varieties. Moderately cold-tolerant types include Tonnage, Choquette, Hall, Lula, Taylor, Monroe, and Brookslate. Varieties with little coldtolerance include Simmonds, Pollock, Dupuis, Nadir, Hardee, and Waldin. PROPAGATION Most avocado varieties do not come true from seed (i.e., a seed will not render the same variety), so they must propagated vegetatively. Cleft grafting is the preferred method of propagation in Florida, although veneer grafting also is used. Young, vigorously growing seedlings are used for rootstocks, and terminals of leafy shoots are used for scion material. Grafting is most successful during the cooler months from Novemr through February or March, but can done from June through March if plant material is available. Established trees may top-worked by cleft grafting scions of the desired varieties on stumps of cut-back trees or by veneer grafting new sprouts arising from stumped trees. Propagation by cuttings and air-layering has not en successful. Currently, little information is available concerning rootstock/scion performance or relationships of Florida avocados. Typically, seedlings of Lula and Waldin are used as rootstocks in Florida cause of their uniformity, vigor, and availability of seeds.

4 The Avocado Page 4 PRODUCTION Less than 1% of the flowers ultimately produce fruit. Some varieties set a large numr of fruit, most of which drop (absice) during early summer, while others set fewer fruit but retain most of them to maturity. Varieties differ in productivity and in regularity of aring, some producing a large crop only every other year. Grafted trees gin to produce on a commercial scale after 3 to 4 years. In Florida, yields from mature trees average 2 to 3 bushels per year (110 to 165 lbs; 50 to 75 kg). However, with good management, considerably tter production can expected. Commercial varieties in Florida mature from June to March, with the greatest production from August through Decemr. Table 3. Some characteristics of Florida avocado varieties. 3 Flower Fruit wt. Fruit Cold tol. Scab Recommended 5 type (oz) color susc. use 1 2 Variety Race Season of maturity Production 4 Home/ Commercial Donnie W May 21 June 31 A Green Low Moderate R Yes May Dupuis W June 15 July 31 A Green Low Low R Yes No Hardee W June 25 July 31 B Red Low High R No No Pollock W June 25 Sept. 1 B Green Low Low R Yes No Simmonds W June 25 Sept. 15 A Green Low Moderate R Yes Yes Nadir GW July 1 Aug. 15 A Green Low Moderate R Yes No Russell W July 1 Aug. 31 A Green Low Moderate R Yes May Brogdon M July 15 Sept. 15 B 8 12 Purple High Moderate MS Yes No Miguel GW July 22 Sept. 15 B Green Low High R Yes Yes Nesbitt GW July 22 Aug. 30 A Green Low Moderate R Yes Yes Tower-2 GW Aug. 1 Sept. 15 B Green Low Moderate R Yes No Ruehle W Aug. 1 Sept. 15 A Green Low High R May No Beta GW Aug. 5 Sept. 15 B Green Moderate High R May May Black Prince GW Aug. 15 Sept. 15 A Purple Moderate High R May Yes

5 The Avocado Page 5 Table 3. Some characteristics of Florida avocado varieties. 3 Flower Fruit wt. Fruit Cold tol. Scab Recommended 5 type (oz) color susc. use 1 2 Variety Race Season of maturity Production 4 Home/ Commercial Loretta GW Aug. 25 Sept. 30 B Green Moderate High M Yes Yes Waldin W Sept. 1 Nov. 1 A Green Low Moderate R Yes No Tonnage G Sept. 15 Oct. 15 B Green High Moderate MS May May Booth-8 GW Oct. 1 Dec. 15 B 9 28 Green Moderate High MS Yes No Nirody GW Oct. 15 Nov. 21 B Green Moderate Moderate R Yes No Marcus GW Oct. 15 Nov. 30 B Green High Moderate R Yes No Booth-7 GW Oct. 15 Dec. 15 B Green Moderate High MS Yes No Choquette GW Oct. 30 Jan. 15 A Green Moderatel Moderate R Yes Yes y High Hall GW Nov. 15 Feb. 1 B Green Moderate High S No No Taylor GW Nov. 15 Feb. 1 A Green High Low MS Yes No Lula GW Nov. 15 Feb. 15 A Green High High S No No Monroe GW Dec. 1 Feb. 15 B Green Moderate High MS Yes Yes Kampong G Dec. 1 March 31 B Green High Low R Yes No Meya G Dec. 7 Feb. 28 A Green High Low R Yes No Reed G Dec. 14 March 7 A 8 18 Green Moderate High R Yes May Brookslate GW Jan. 14 March 7 A Green High High R May May Race: W West Indian; G Guatemalan; M Mexican Season of maturity may not correspond with legal maturity. Cold tolerance Scab susceptibility: R resistant; MS moderately susceptible; S susceptible Recommended use: home planting and commercial planting

6 The Avocado Page 6 SPACING AND PRUNING Planting distances depend on soil type and fertility, current technology, and economic factors. In commercial groves, trees are planted from 15 to 25 feet (4.6 to 7.6 m) in rows and 25 to 30 feet (7.6 to 9.1 m) tween rows. Dooryard trees should planted 25 to 30 feet (7.6 to 9.1 m) away from buildings and other trees. Formative pruning during the first 2 years may desirable to encourage lateral growth and multiple framework branching. Commercially, after several years of production it is desirable to occasionally cut back the tops of the trees to 16 to 20 feet (4.9 to 6.1 m). This reduces spraying and harvesting costs and possible storm damage. This operation should done soon after harvest for early varieties, but after danger of frost has passed for late varieties. Severe topping and hedging (used to reduce canopy width) do not injure trees, but reduce production for one to several seasons. Planned tree removal is an option that should seriously considered for commercial plantings fore overcrowding and reduced yields gin. Preliminary studies to rejuvenate non-productive mature orchards with very tall (30 to 40 ft; 9.1 to 12.2 m) trees suggest that production on a per acre basis can improved when selected trees are removed and remaining trees are topped at 16 to 22 feet (4.9 to 6.7 m). This is cause the lower canopy of remaining trees is re-established and production per tree in the orchard exceeds yields of overcrowded trees. SOILS The avocado does not tolerate flooding or poorly drained soils, but is adapted to many types of well-drained soils. Continuously wet or flooded conditions often result in decreased growth and yields, as well as nutrient deficiency symptoms. Under these conditions, trees are highly susceptible to root infection by Phytophthora fungi. Trees grow well and produce satisfactory yields in the sandy and limestone soils of Florida if maintained with a good fertilizer program. FERTILIZER In Florida, young trees should fertilized every 1 to 2 months during the first year, ginning with 1/4 lb (114 g) of fertilizer and increasing to 1 lb (455 g) per tree. Thereafter, three or four applications per year in amounts proportionate to the increasing size of the tree are sufficient. Mature trees should receive 150 to 200 lbs (68 to 91 kg) of nitrogen and potash per acre per year split into three to four applications. Fertilizer mixtures containing 6 to 10% nitrogen (N), 6 to 10% available phosphoric acid (P O ), 6 to 10% potash (K O), and 2 to % magnesium (Mg) give satisfactory results with young trees. For aring trees, available phosphoric acid should reduced to 2 to 4%. Examples of commonly available commercial mixes include 6(N)-6(P O )-6(K O)-2(Mg) and 8(N)-3(P O )-9(K O)-3(Mg) Plants growing in calcareous soils should receive annual nutritional sprays of copper, zinc, manganese, and boron for the first 4 to 5 years. Thereafter, only zinc, manganese, and possibly boron are necessary. Avocado trees are susceptible to iron deficiency under alkaline conditions. Iron deficiency can prevented or corrected by periodic soil applications of iron chelates formulated for alkaline conditions. IRRIGATION Conclusive information on irrigation rates and frequencies for Florida avocado varieties is not currently available. However, observations suggest irrigation during dry periods may increase tree growth and development as well as fruit set and production. INSECT PESTS Many insect pests attack avocados, but they seldom limit fruit production significantly. Insect infestations are not predictable and control measures are justified only when large populations occur. Currently, the most important insect pests in Florida are: Avocado Looper (Epimecis detexta) Pyriform Scale (Protopulvinaria pyriformis) Dictyospermum Scale (Chrysomphalus dictyospermi) Avocado Red Mites (Oligonychus yothersi) Borers (e.g., Ambrosia etles, Xylosandrus sp.) Avocado Lace Bugs (Acysta perseae) Red-banded Thrips (Selenothrips rubrocinctus) Growers should contact the University of Florida County Cooperative Extension Service for recommended control measures.

7 The Avocado Page 7 DISEASES Successful control of foliar and fruit diseases caused by fungi requires that all susceptible parts of the plant thoroughly coated with the fungicide fore infection occurs. Sprays applied after infection (which usually occurs several days fore the disease is evident) often have limited to no effect on disease development. Sprays must re-applied as new tissues come exposed by growth and as spray residues are reduced by weathering. A successful program depends on: 1) Use of the right amount of a recommended fungicide and adjuvant, if required. 2) Timely applications fore infection is most likely to occur. 3) Thorough coverage of susceptible parts. Growers should contact the University of Florida County Cooperative Extension Service for current control recommendations for the diseases discussed low. Cercospora spot (Cercospora purpurea). Infection appears on fruits and leaves as small, angular, dark brown spots which coalesce to form irregular patches. These spots have a yellow halo. Fruit lesions are frequently the point of entry for other decay organisms, such as the anthracnose fungus. Infection usually occurs during the summer months. Begin a spray program for Cercospora prevention about May 1st and continue until harvest. Avocado scab (Sphaceloma perseae). The scab fungus readily infects young, succulent tissues of leaves, twigs and fruit. These tissues come resistant as they mature. Lesions appear as small, dark spots visible on both sides of the leaves. Spots on leaf veins, petioles and twigs are slightly raised, and oval to elongated. Severe infections distort and stunt leaves. Spots on fruits are dark, oval and raised and eventually coalesce to form cracked and corky areas which impair the appearance but not the internal quality of the fruit. Begin a spray program for scab prevention when bloom buds gin to swell and continue spraying until harvest. The most susceptible commercial variety in Florida is Lula. Anthracnose (Colletotrichum gloeosporoides). Anthracnose infection is important only on fruits. Infections occur through lesions caused by other organisms such as scab and Cercospora spot, or mechanical injuries. The fungus does not develop in actively growing fruits but causes a rot as the fruit ripens. Fruit lesions start as circular brown to black spots which enlarge, come sunken, and crack. Avocado root rot (Phytophthora cinnamomi). Trees in areas with poorly drained soils and/or which are subject to flooding are likely to affected by this fungus. This is the most serious disease in most avocado producing areas of the world. Although many trees are infected with the fungus in Florida, the disease appears to serious only if trees are subjected to flooded conditions. Leaves of infected trees may pale green, wilted, or dead, and terminal branches die back in advanced stages of the disease. Feeder roots come darkened and decayed, and severely affected trees usually die. Powdery mildew (Oidium sp.). Powdery mildew covers undersides of leaves with a white powdery growth. Later, the white mildew disappears leaving dark, reticulate markings, which appear from the upper side as yellowish areas. Usually not serious enough to require control measures, this disease is most prevalent during the dry season. Sun-blotch (Caused by a viroid). Symptoms of infection include sunken yellow or whitish streaking or spotting and distortion of twigs, leaves, and fruit. It is transmitted through buds, seeds, and root-grafting of infected trees. There is no control for this disease, and infected trees should destroyed. This disease is rare in Florida. Algal Leaf Spot (Cephaleuros sp.). Symptoms appear first on upper leaf surfaces as green, yellowish-green, or rust-colored, roughly circular spots. This disease is most prevalent during summer and fall months. Diplodia Stem-end Rot (Diplodia sp.). This rot disease gins at the stem end of the fruit and develops as the fruit softens. It is usually only a problem with immature fruit after harvest and can prevented by harvesting only mature fruit. RIPENING AND STORAGE Avocado fruits do not ripen on the tree. A mature fruit ripens in 3 to 8 days after it is picked. Florida avocados ripen st at temperatures of 60 to 75 F (16 to 24 C). At higher temperatures, fruit ripen unevenly and develop off-flavors. Hydro-cooling and cold storage delays ripening and facilitates shipping to distant markets. The lowest safe storage temperatures are 55 F (13 C) for West Indian and 40 F (4 C) for most other Florida

8 The Avocado Page 8 varieties. Chilling injury is characterized by a browning or darkening of the skin and/or grayish-brown discoloration of the flesh. USES Compared to other fruits, avocados are highly nutritious, a good source of potassium and a moderate source of Vitamin A. Avocado fruit does not contain cholesterol, and Florida varieties have less total fats than California varieties. Cooking impairs flavor and appearance of avocados, but many satisfactory frozen products can prepared. The most popular ways of serving the avocado are in salads, as appetizers, dips, and as "guacamole". The avocado has a variety of culinary uses and the delicate flavor appeals to the gourmet.