Avocado - Crop Post-Harvest: Science and Technology - page 169

INSECT PESTS
Johansen et al . (1999) published a taxonomic study of 41
Mexican insect species of Thysanoptera inhabiting Persea
americana Mill floral and foliar structures. They reported
that a total of 38 species are phytophagous, whereas only
three are predators. Only six phytophagous species can be
considered as primary pests for the young fruit or foliar
structures, and the other 32 can be considered as incidental
visitors. The three predatory species live in both natural
ecosystems and avocado agricultural ecosystems. The
cacao thrips ( Selenothrips rubrocinctus ) and greenhouse
thrips ( Helipthrips haemorrhoidalis ) are the most com-
mon and relevant for avocado in the world. The damage
produced by these pests can result in up to 50% crop loss
(Adame 1994; Gallegos 1983). Even though 31 species of
insects are potentially harmful to Chilean avocado (Prado
1991), only 9 species are considered as economically
important. Gallegos (1983) reported 46, and Coria (1993)
listed 11 species in the state of Michoacán, Mexico.
However, as is the case in Chile, only a few pest species
are economically important for avocado crops. Avocado
pests in Mexico have been estimated to affect 14% of
avocado production and diminish 10% of fruit quality,
increasing the cost by 23% (Vidales-Fernández &
Alcántar-Rocillo 1999).
Thrips, of the species, Liothrips persea Watson, Scirto-
thrips aceri Moulton, Frankiniella cephalica, Heliothrips
haemorrhoidalis (Insecta:Thysanoptera: Thriphidae) are
found in Florida, California, Mexico, Central and South
America, Argentina and Chile, but their damage is reduced
in avocado cultivated between 1900 and 2400 m of altitude.
Thrips are one of the most relevant pests for avocado
cultivars in Mexico. They can cause malformation of the
fruit and premature falling from the tree and damage the
vegetative tissue when feeding, producing lesions that
become entry points for micro organisms such as
Sphaceloma perseae (González-Hernández et al . 1999).
The major damage is caused when the thrips feed on young
fruits, producing crest-shaped malformations of the exocarp,
which are more evident in ripe fruit. A natural biological
control exists when wasps ( Desycapus pariopennis Gaham,
Trichogramatidae family) parasitise the thrips eggs. There
are other predators such as Leptothrips , Franlinothrips and
Watsoniella . An important cultural control is the elimination
of weed, and keeping the orchard clean. This is a pest easily
controlled by chemical pesticides, such as Malathion and
parathion. For severe attacks, pyrethrines such as fluvalinates
are recommended (Adame 1994; Gallegos 1983). Chemical
pesticides should be applied when 10% and 100% of flowers
appear, and when fruits are in bud stage.

Small seed weevil, of the species Conotrachelus
perseae Barber (Coleoptera: Curculiondae: Crypto-
rhynchinae), is found in the eastern central region of
Mexico and northern parts of Central America, Guatemala
and Panama. They tunnel, forming a gallery throughout
the pulp until they arrive at the seed, which is usually
destroyed. Highly infected areas can affect up to 85% of
the fruit, destroy the seeds and notably affect the
production, since this situation induces the falling of the
fruit from buds to maturity (Martinez & Adame 1987).
An integrated management is required in order to control
the pest, including cultural labours, chemical and legal
control, since that this is a pest covered by quarantine
regulations in several countries. Cultural control consists
in the destruction of infested fruits, together with soil
labour to destroy the pupa. Chemical control is carried
out using methylic parathion or Malathion in powder
(2% to 3%) applied to the soil during the emergence of
adults, or as a spray at doses of 1 to 2 L / 1000 L of water
every 10 days while adults are present. Legal control
includes the establishment of campaigns for prevention
in free zones and quarantines to avoid dispersion
(Bravo et al . 1988; Martínez & Adame 1987). The large
seed weevil, Heilipus lauri Boheman (Coleptera:
Curculionidae: Hylobiinae), is found in the western
central region of Mexico, but not in the avocado cultivars
of Michoacán. Other species of this weevil are
H. sguanosus found in Florida and California, the West
Indies, and in the Virgin Islands; H. pihieri in Central
America; H. cartagraphus and H. montei in Brazil; and
H. persea in Panama. Females lay 1 to 2 oval-shaped
eggs in a previously made cavity under the epidermis of
the fruit, which at first are green in colour and later
become darkened. They tunnel through the flesh of the
fruit, forming a gallery that extends to the seed, which is
usually destroyed. Furthermore, they produce secondary
rotting of the flesh and the seed. The pupae develop
inside the fruit after 14 to 16 days. This pest can destroy
the flesh, seeds, and cause a premature falling of the
fruits (Bravo et al . 1988; Gallegos 1983). Optimum
control of this pest is achieved when combining chemical
and cultural controls. The spraying of the foliage every 8
to 10 days after adult appearance is recommended, using
phosphate-containing chemicals such as methylic
parathion, Malathion and ethylic gustathion at doses of
1-2 L in 1000 L of water. As a cultural control, it is
important not to leave fruit on the tree after harvest, to
gather all fallen fruits and destroy them. A biological
control that gives 20% efficiency can be achieved with
Bracon sp (Bravo et al . 1988; Gallegos 1983).