MIMEOGRAPHED REPORT SUB70-1 August, 1969
University of Florida
/ Institute of Food and Agricultural Scienes
SUB-TROPICAL EXPERIMENT STATION HUME LIBRARY
18905 S. W. 280 Street
Homestead, Florida 33030 SP 11 1972
CONSIDERATIONS FOR TREATING AVOCADOS FOR INSE PFSTSUniv of Florida
D. 0. Wolfenbarger, Entomologist
Insects are not limiting factors in Florida avocado production,
except perhaps in local areas for short periods. A number of spe-
cies have existed in low numbers on avocados for many years, includ-
ing the avocado tree girdler, Heilipus sauamosus Lec.; avocado lace
bug, Acvsta perseae Heid.; avocado leafhopper, Idona minuenda (Ball);
several scale insects and caterpillars of different species. These
are always with us awaiting conditions favorable for rapid multipli-
Favorable Conditions.-- Favorable conditions is a term often used to
designate a situation in which insect pests increase to harmful
numbers and about which too little is known. Injurious populations
of the avocado tree girdler developed about 1947 from some unknown
condition or conditions. Although hurricanes were blamed for bring-
ing about favorable conditions, there were perhaps some other respon-
sible factors. Red-banded thrips, Selenothrips rubrocinctus (Giard.),
were serious on many avocado (and mango) trees about 1947-48 but
have seldom been observed since that time. During the months of
January and February the avocado red mite, Oliqonychus vothersi (McG.)
causes leaves on some trees in some groves to become red colored,
while trees in other groves are unaffected. A question may be asked
"When will conditions be favorable for the development of what pest
Mirids.-- A number of species of small sucking insects known as
mirids feed on opening buds, leaves, flowers and small fruit.
Attacks seem to affect especially flowers and recently set fruit
causing them to drop or the fruit to become "pimply" or distorted
as they develop. Wounds on fruit may serve as a point of entry for
decay organisms. Feeding on buds causes punctures which result in
holes in leaves.
Mirids usually appear during bloom and early fruit setting stage.
It is suggested that weeds and grass in and around the grove be
mowed as closely as practicable in order to reduce harboring places
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Benzene hexachloride (10% gamma-isomer content) at 2 pounds, or
lindane (25% gamma-isomer content), at 1 pound per 100 gallons, has
given control of mirids for two decades. Carbaryl (Sevin) 80 W has
had limited use but has given satisfactory control of mirids at
1 to 1 pounds per 100 gallons of water. Carbaryl lacks official
approval for use on avocados and thus must be used before fruit set
in order to avoid contamination of fruit. Spray applications during
flowering should be made in late afternoon to reduce losses of honey
Lepidopterous Larvae.-- A number of species of Lepidoptera (cater-
pillars or worms) feed on avocado leaves but are usually heavily
parasitized and cause little damage.
Span-worm, Epimecis detexta Wlk., infestations have been observed
more frequently than in former years. In one instance recently a
high population followed two applications of benzene hexachloride.
The newer effective insecticides that can be recommended against
lepidopterous larvae during the fruit bearing period have not been
approved for use on avocados. Lead arsenate has approval provided
excess residues are removed at harvest time. It is recommended for
use at 3 pounds per 100 gallons of water.
Ambrosia beetles.-- Ambrosia beetles can be serious since they bur-
row into living twigs, branches and even tree trunks. Tissues above
the beetle entrance or burrows usually die. Infestations in avoca-
dos, however, usually occur on lower branches in shaded locations.
Since these branches are often unproductive, their death may not
result in loss to the grower. Removal and destruction of infested
twigs and branches is recommended as a control. Benzene hexachloride,
at 2 pounds of 10% gamma-isomer per 100 gallons of water may be used
if an insecticide is needed.
Avocado red mite.-- Infestations of the avocado red mite appear in
December, January and February. This mite attacks older leaves which
will fall before the fruit develops. It may be questioned, there-
fore, whether the cost of mite control is justified. There is
insufficient evidence to show that yields are increased as a result
of mite control. Sulfur gives satisfactory control unless the
infestation is severe or repeated applications are needed. A number
of the newer miticides such as Morestan, Morocide and AzOdrin are
effective but have not been approved for use on avocados. Kelthane
(dicofol) is sometimes injurious to avocados, hence it cannot be
Avocado leafhopper.--This pest has been of little or no concern to
growers. Populations of this pest have been increasing in recent
years. Leafhoppers are often insidiously destructive to crop plants
and they are being watched on the avocado.
Flower thrips.-- Infestations are common in practically all flowers.
They may aid in pollination and they may occasionally become so
abundant as to reduce fruit set. Two or three thrips per flower
may be of little consequence but when the average number reaches
15-25, control measures should be used.
Local Variabilities.-- A very important factor in avocado insect
pest control is the variability of pest populations. For example,
severe infestations of the avocado white fly, Trialeurodes
floridensis (Quaint.), and a bagworm, O-keticus abbotii Grt., have
been observed in a grove while another grove a few miles away was
uninfested, A Casuarina sp. hedge surrounding the first mentioned
grove appears to have boen a factor affecting the infestations.
Trees around buildings or near dusty roadways may be found more
heavily infested with scale insects than those at more remote sites.
Many other species may be present awaiting conditions favorable for
A General Recommendation.-- Grove owners or caretakers should
examine regularly all trees for insect pests so that they are aware
of conditions in the grove at all times. Insecticides should be
used only when needed. Although certain groves have characteristic
histories of pests, too much reliance cannot be placed on earlier
occurrences as a guide to the current situation or what can be
expected in the future. Consult with the county agent or extension
personnel for an evaluation of infestations.