Group Title: Circular
Title: The avocado
Full Citation
Permanent Link:
 Material Information
Title: The avocado
Series Title: Circular
Physical Description: 7 p. : ; 28 cm.
Language: English
Creator: Crane, J.H ( Jonathan Henry ), 1952-
Balerdi, C. F ( Carlos F )
Campbell, Carl W
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1992
Subject: Avocado -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: J.H. Crane, C.F. Balerdi, and C.W. Campbell.
General Note: Title from caption.
General Note: "February 1992."
 Record Information
Bibliographic ID: UF00014460
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6897
ltuf - AJG5669
oclc - 26848028
alephbibnum - 001752712

Full Text


The Avocado

J.H. Crane, C.F. Balerdi, and C.W. Campl

Florida Cooperative Extension Service / Institute of Food and A

Scientific name: Persea americana Miller

Common names: avocado, avocado-pear,
aguacate (Spanish)

Family: Lauraceae

Origin: Avocados are indigenous to tropical
America and three ecological races, Mexican, Gua-
temalan, and West Indian, are recognized.

Distribution: Avocados are grown in tropical
and subtropical areas of the world. In Florida, com-
mercial production is primarily in Dade and Collier
Counties; however, small plantings and isolated
trees are found in warm locations throughout the

History: Avocados have been cultivated in
tropical America since pre-Columbian times. The
first recorded importation into Florida was in 1833
and into California in 1856.

Importance: One of the important fruits in the
American tropics, the avocado is grown commer-
cially in many areas of the world including Mexico,
Brazil, Australia, Israel, Chile, tropical Africa, Cali-
fornia, and Florida.

Tree: A medium (30 ft; 9.1 m) to large (65 ft;
19.8 m) tree, the avocado tree is classified as an ev-
ergreen, although some varieties lose their leaves
for a short time before 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.

*Assistant Professor, Multi-County Tropical Fruit Crops Agent,
and Emeritus Professor, respectively; Fruit Crops Department,
Institute of Food and Agricultural Sciences, University of
Florida, Gainesville,32611.

Leaves: Leaves are 3 to 16 in. (7.6 to 40.(-cii)
in length and variable in shape (elliptic, oval, lan-
ceolate). They are often pubescent and reddish
when young, becoming smooth, leathery, and dark
green when mature.

Inflorescence: The many-flowered lateral in-
florescences are borne in a pseudoterminal position.
The central axis of the inflorescence terminates in a
shoot. Flowers are perfect, yellowish green, and 3/8
to 1/2 in. (1 to 1.3 cm) in diameter.

Fruit: The fruit is a berry, 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 weigh
from a few ounces to 5 pounds (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 cal-
endar date and weight or size. The specific dates,
weights, and sizes used to determine maturity vary
by variety. An alternative method in some places
(i.e., California) has been to harvest when the fruit
contain a specified minimum oil content. However,
this method has not proved useful for the varieties
of avocados grown in Florida.

Pollination: Varieties are classified into A and
B types according to the time of day when the fe-
male and male flower parts become reproductively
functional (Table 1 on p. 2). New evidence indi-
cates avocado flowers may be both self- and cross-
pollinated under Florida conditions. Self-pollina-
tion occurs during the second flower opening when
pollen is transferred to the stigma while cross-polli-
nation may occur when female and male flowers
from A and B type varieties open simultaneously.


Circular 1034

y raurbeF 1 992

*:?~l~:~~CgTII C k: R~"?i~:Y~ :r~~"P'17~

Table 1. Behavior of a Type A and Type B avocado flower.z

Flower type
Day Time A B

1st day, A.M. Flower opens
Stigma receptive

P.M. Flower closed Flower opens
Stigma receptive

Night / / Flower closed Flower closed

2nd day, A.M. Flower closed Flower opens again
Pollen sheds
Stigma may or may
SCIE t't not be receptive

P.M. Flower opens again Flower closed
Pollen sheds
Stigma may or may
not be receptive
z, Flowers not pollinated are shed.

Self-pollination appears to be primarily caused
by wind, whereas cross-pollination may be effected
by large flying insects such as bees and wasps.

Varieties vary in the degree of self- or cross-polli-
nation 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 advanta-
geous to plant them in rows alternating with other
varieties (A types) which bloom simultaneously to
facilitate adequate pollination.

Avocado varieties are classified in 3 groups,
known as the West Indian, Guatemalan and Mexi-
can "races", with distinguishing characteristics
summarized in Table 2.

Early varieties are usually of West Indian and
Mexican origin, whereas midseason and late variet-
ies are hybrids between the races and have inter-
mediate characters. Some characteristics of
Florida avocado varieties are summarized in Table
3 (on p. 4).

West Indian and some hybrid varieties are best
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 low-
land 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 be difficult
to find plants of these varieties. Moderately cold-
tolerant types include 'Tonnage', 'Choquette', 'Hall',
'Lula', 'Taylor', 'Monroe', and 'Brookslate'. Varieties
with little cold-tolerance include 'Simmonds', 'Pol-
lock', 'Dupuis', 'Nadir', 'Hardee', and 'Waldin'.

Most avocado varieties do not come true from
seed and must be propagated vegetatively. Cleft
grafting is the preferred method of propagation in
Florida, although veneer grafting is also used.

Young, vigorously growing seedlings are used for
rootstocks and terminals of leafy shoots are used
for scion material. Grafting is most successful dur-
ing the cooler months from November through Feb-
ruary-March but can be done from June-March if
plant material is available. Established trees may
be top-worked by cleft-grafting scions of the de-
sired 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 been successful.

Currently, little information is available con-
cerning rootstock/scion performance or relation-
ships of Florida avocados. Typically, seedlings of
'Lula' and 'Waldin' are used as rootstocks in
Florida because of their uniformity, vigor, and
availability of seeds.

Less than 1% of the flowers ultimately produce
fruit. Some varieties set a large number 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 bearing, some producing a large crop
only every other year.

Grafted trees begin to produce on a commercial
scale after 3 to 4 years. In Florida, yields from ma-
ture trees average 2 to 3 bushels per year (110 to 165
lbs; 50 to 75 kg). However, with good management,
considerably better production can be expected.

Commercial varieties in Florida mature from June
to March, with the greatest production from August
through December.

Table 2. Characteristics of West Indian, Guatemalan, and Mexican races of avocados.

West Indian Guatemalan Mexican

Origin Tropical lowlands Tropical highlands Tropical highlands

Foliage No odor No odor Anise-scented

Blooming season Feb. to March March to April Jan. to Feb.

Maturity season May to Sept. Sept. to Jan. June to Oct.

Development 5 to 8 months 10-15 months 6 to 8 months
period (fruit
set to maturity)

Fruit size 1 to 5 pounds 1/2 to 5 pounds Not over 1 pound
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 Med. to high Med. to high

Cold hardiness
Young trees 28 to 30 F 26 to 280 F 24 to 260 F
-2to-1 C -3to -20C -4to -3 C

Mature trees 25 to 300 F 21 to 250 F 18 to 250 F
-4 to -1 C -6 to -40 C -8 to -40 C
z, Tree response to freezing temperatures is influenced by tree health, stage of growth, and cultural practices.

Table 3. Some characteristics of Florida avocado varieties.

Season Fruit Recom.
of Flower Cold Scab usez
Variety Race1 maturity2 type wt (oz) color3 tol.4 Prod.5 susc.6 H C

Donnie W May 21- A 12-20 G L M R Y M
June 31
Dupuis W June 15- A 12-24 G L L R Y N
July 31
Hardee W June25- B 12-24 R L H R N N
July 31
Pollock W June 25- B 18-40 G L L R Y N
Sept. 1
Simmonds W June 25- A 16-34 G L M R Y Y

Nadir GW

Russell W

Brogdon M

Miguel GW

Nesbitt GW

Tower-2 GW

Ruehle W

Beta GW

Black Prince GW

Loretta GW

Waldin W

Fairchild GW

Tonnage G

Booth-8 GW

Nirody GW

Marcus GW

Booth-7 GW

Choquette GW

Sept. 15
July 1-
Aug. 15
July 1-
Aug. 31
July 15-
Sept. 15
July 22-
Sept. 15
July 22-
Aug. 30
Aug. 1-
Sept. 15
Aug. 1-
Sept. 15
Aug. 5-
Sept. 15
Aug. 15-
Sept. 15
Aug. 25-
Sept. 30
Sept. 1-
Nov. 1
Sept. 1-
Nov. 30
Sept. 15-
Oct. 15
Oct. 1-
Dec. 15
Oct. 15-
Nov. 21
Oct. 15-
Nov. 30
Oct. 15-
Dec. 15
Oct. 30-
Jan. 15

A 10-22

A 16-24

B 8-12

B 18-26

A 14-26

B 12-20

A 10-20

B 16-24

A 16-28

B 20-36

A 14-28

A 16-26

B 14-24

B 9-28

B 15-24

B 18-48

B 10-20

A 18-40





































Season Fruit Recom.
of Flower Cold Scab usez
Variety Race1 maturity2 type wt (oz) color3 tol.4 Prod.5 susc.6 H C

Hall GW Nov. 15- B 20-30 G M H S N N
Feb. 1
Taylor GW Nov. 15- A 12-18 G H L MS Y N
Feb. 1
Lula GW Nov. 15- A 14-24 G H H S N N
Feb. 15
Monroe GW Dec. 1- A 24-40 G M H MS Y Y
Feb. 15
Kampong G Dec. 1- B 14-24 G H L R Y N
March 31
Meya G Dec. 7- A 10-16 G H L R Y N
Feb. 28
Reed G Dec. 14- A 8-18 G M H R Y M
March 7
Brooks- GW Jan. 14- A 10-22 G H H R M M
late March 7

1, Race, W: West Indian; G: Guatemalan; M: Mexican
2, Season of maturity may not correspond with legal maturity
dates set by the Avocado Committee, which vary year to year.
3, Fruit color, G: green; P: purple; R: red
4, Cold tolerance, H: high; M: moderate: L: low
5, Production, H: high; M: moderate; L: low
6, Scab susceptibility, R: resistant; MS, moderately susceptible; S: susceptible

7, Recommended use, H: home planting; C: commercial; Y:

Spacing and pruning
Planting distances depend on soil type and fertil-
ity, current technology, and economic factors. In
commercial groves, trees are planted from 15 to 25
ft (4.6 to 7.6 m) in rows and 25 to 30 ft (7.6 to 9.1
m) between rows. Dooryard trees should be
planted 25 to 30 ft (7.6 to 9.1 m) away from build-
ings and other trees.

Formative pruning during the first two years
may be desirable to encourage lateral growth and
multiple framework branching. Commercially, af-
ter several years of production it is desirable to oc-
casionally cut back the tops of the trees to 16 to 20
ft (4.9 to 6.1 m), to reduce spraying and harvesting
costs and to reduce storm damage. This operation
should be done soon after harvest for early varieties
but after danger of frost has passed for late variet-
ies. Severe topping and hedging (used to reduce
canopy width) do not injure trees, but reduce pro-
duction for one to several seasons.

yes; N: no; M, maybe

Planned tree removal is an option that should be
seriously considered for commercial plantings. Pre-
liminary studies suggest that production on a per
acre basis can be maintained or improved when se-
lected trees are removed. This is because produc-
tion of remaining trees in the orchard equals or ex-
ceeds yields of overcrowded trees.

The avocado does not tolerate flooding or poorly
drained soils, but is adapted to many types of well-
drained soils. Continuously wet or flooded condi-
tions 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.

In Florida, young trees should be fertilized every
one to two months during the first year, beginning
with 1/4-pound (114 g) of fertilizer and increasing
to one pound (455 g) per tree. Thereafter, three or
four applications per year in amounts proportionate
to the increasing size of the tree are sufficient. Ma-
ture trees should receive 150 to 200 pounds (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% avail-
able phosphoric acid (P205), 6 to 10% potash (O20),
and 2 to 6% magnesium (Mg) give satisfactory re-
sults with young trees. For bearing trees, available
phosphoric acid should be reduced to 2 to 4%. Ex-
amples of commonly available commercial mixes
include 6(N)-6(P20,)-6(K20)-2(Mg) and 8(N)-

Plants growing in calcareous soils should receive
annual nutritional sprays of copper, zinc, manga-
nese, and boron for the first four to five years.
Thereafter, only zinc, manganese, and possibly bo-
ron are necessary. Avocado trees are susceptible to
iron deficiency under alkaline conditions. Iron defi-
ciency can be prevented or corrected by periodic soil
applications of iron chelates formulated for alkaline

Conclusive information on irrigation rates and
frequencies for Florida avocado varieties is not cur-
rently available. However, observations suggest
irrigation during dry periods may increase tree
growth and development and fruit set and produc-

Many insect pests attack avocados but they sel-
dom limit fruit production significantly. Insect in-
festations are not predictable and control measures
are justified only when large populations build up.
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 beetles,
Xylosandrus sp.), Avocado Lace Bugs (Acysta
perseae), and Red-banded Thrips (Selenothrips
rubrocinctus). Growers should contact the Univer-
sity of Florida County Cooperative Extension Ser-
vice for recommended control measures.

Successful control of foliar and fruit diseases
caused by fungi requires that all susceptible parts
of the plant be thoroughly coated with the fungicide
before infection occurs. Sprays applied after infec-
tion (which usually occurs several days before the
disease is evident) often have limited to no effect on
disease development. Sprays must be re-applied as
new tissues become exposed by growth and as
spray residues are reduced by weathering. A suc-
cessful program depends on (1) use of the right
amount of a recommended fungicide and adjuvant,
if required; (2) timely applications before infection
is most likely to occur: and (3) thorough coverage of
susceptible parts. Growers should contact the Uni-
versity of Florida County Cooperative Extension
Service for current control recommendations for the
diseases discussed below.

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 fun-
gus. Infection usually occurs during the summer
months. Begin a spray program for Cercospora pre-
vention 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 be-
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 dis-
tort 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 be-
gin to swell and continue until harvest. The most
susceptible commercial variety in Florida is 'Lula'.

(Colletotrichum gloeosporioides)
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, become sunken, and

Avocado root rot
(Phytophthora cinnamomi)
Trees in areas with poorly drained soils and/or
which are subject to flooding are likely to be affected
by this fungus. This is the most serious disease in
most avocado producing areas of the world. Al-
though many trees are infected with the fungus in
Florida, the disease only appears to be serious if
trees are subjected to flooded conditions. Leaves of
infected trees may be pale green, wilted, and necrotic
and terminal branches die back in advanced stages
of the disease. Feeder roots become 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. Usu-
ally 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 be
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 circu-

lar spots. This disease is most prevalent during
summer and fall months.

Diplodia stem-end rot (Diplodia sp.)
This rot begins at the stem end of the fruit and
develops as the fruit softens. It usually is only a
problem with immature fruit after harvest and can
be prevented by harvesting only mature fruit.

Ripening and storage
Avocado fruits do not ripen on the tree. A ma-
ture fruit ripens in three to eight days after it is
picked. Florida avocados ripen best at tempera-
tures of 60 to 75o F (160 to 240 C). At higher tem-
peratures, fruit ripen unevenly and develop off-fla-
vors. Hydro-cooling and cold storage delays ripen-
ing and facilitates shipping to distant markets.
The lowest safe storage temperatures are 55 F (130
C) for West Indian and 40 F (40 C) for most other
Florida varieties. Chilling injury is characterized
by a browning or darkening of the skin and/or gray-
ish-brown discoloration of the flesh.

Compared to other fruits, avocados are highly
nutritious and 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 avoca-
dos, but many satisfactory frozen products can be
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.

Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June
30,1914 Acts of Congress; and is 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. Single copies of extension publications (excluding 4-H and youth
publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-state purchasers
Isavailablefrom C.M.Hinton, Publications Distribution Center, IFAS Building 664, Universityof Florida, Gainesville, Florida32611. Before publicizing ..
this publication, editors should contact this address to determine availability. Printed 2/92.

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs