Avocado - Crop Post-Harvest: Science and Technology - page 170

Seed moth, caused by Stenoma catenifer Walsingham
(Lepidoptera: Stenomidae), is one of the most widely
distributed avocado pests in Mexico, being found in the
east and coastal zones of the country. It is also found in
Guatemala, Costa Rica, Panama, Colombia, Venezuela,
Peru, Bolivia, Ecuador, Brazil and Argentina. The eggs are
deposited on or near the fruit, and also on tender branches.
Upon hatching, whitish larvae emerge and penetrate the
fruit forming galleries which extend to the seed, and in
branches extend to the central cylinder. Seed moths can
penetrate fruits of any size and destroy the seed completely
(Bravo et al . 1988; Gallegos 1983). A combination of
chemical and cultural control is needed. The cultural
control consists of pruning the affected branches, gathering
the fallen fruit and burying or incinerating it. Chemical
control can be used for adult insects by spraying
phosphate-pesticides, carbamate, or piretroid pesticides,
such as Malathion, gustathion, sevin and permetrines in
commercial doses. Phosphate-containing pesticide in pow-
der form can also be applied at 2% to the soil when the
fruit begins to fall during the emergence of adults
(Bravo et al . 1988; Gallegos 1983).

QUARANTINE TREATMENTS
Avocados grown in fruit fly infested areas require
quarantine treatments to be marketed in certain countries.
Methyl bromide (MBr) treatment is an APHIS approved
treatment for Mediterranean fruit fly, but can result in a
significant reduction in fruit quality. Avocado fruit treated
with MBr can exhibit some external damage, ripening 2 to
4 days earlier than the non-fumigated controls. Pitting and
other visual damage caused by fumigation is commonly
masked in the case of cultivars with purple or black fruit
when the fruit ripen and achieve a dark colour. The cultivars
with least damage are those with purple or black skin. MBr
fumigation does not affect the flesh as much as the skin.
Flesh colour and flavour are commonly acceptable in most
cultivars and the former is usually equal to that of the
controls in appearance. Fumigated fruit, however,
commonly show more internal browning in certain cultivars
with visibly affected vascular fibre throughout the flesh
(Ito & Hamilton 1980).
Low-temperature disinfestations can be used, but can
also result in fruit damage. Tolerance to temperatures
which can be used for low temperature disinfestations can
be imparted by pre-treatments at 38°C (Sanxter et al . 1994;
Woolf et al . 1995: Roman & Yahia 2000a, 2000b) or low
temperature conditioning (Woolf et al . 2002). Commercial
disinfestations treatment in use for Queensland fruit fly in
'Hass' avocados is at 6°C to 8°C for 3 to 5 days followed
by 16 days at <1°C (Hofman et al . 2002). However, this
low-temperature disinfesting treatment may not be effec-
tive for all fruit fly species because of tolerance differences
in insects and also of different avocado cultivars. The
potential for hot water treatment (HWT) to improve quality
of 'Hass' avocado following cold disinfestations for fruit
flies was investigated by Hofman et al . (2002). HWT at
38-42°C for 20-60 min significantly reduced skin damage
caused by cold disinfestations, with 40°C for 30 min, 41°C
for 20-30 min and 42°C for 25-30 min resulting in the
greatest reduction (Hofman et al . 2002). HWT also reduced
body rots in ripe fruit, with 40°C and 41°C for 30 min
being consistently the most effective. Treatment at 42°C
increased body rots compared to the other HWTs in one
season, and there was no benefit of HWT times longer than
30 min. The severity of vascular browning (VB) and
mesocarp discolouration (MD) in ripe fruit was generally
low, and increased following cold disinfestations. Hot
water treatments reduced VB severity but had no effect on
MD. Treatment at 41°C for 25-30 min and 42°C for 25 min
increased the percentage of externally acceptable fruit (less
than 5% of the skin area with defects) from 0% to about
80% 3 days after removal from disinfestations. The same

Control measures
In order to establish a good strategy for integral pest con-
trol, thresholds and levels of economical damage need to
be determined. This can help to reduce the frequency of
fumigation, lower the crop handling costs, as well as to
increase the production. In Mexico, only four pesticide
products are recommended for chemical control: (1) par-
afinic petroleum oil, (2) Malathion CE 47, (3) Methylic
parathion and (4) Permetrine. In Chile, the presence of a
large fauna of biological controllers has helped to contain
potential avocado pests. However, there is no doubt that the
use of pesticides in the orchards contribute to maintain this
situation. Different pests that sometimes need to be
restrained can be handled with selective pesticides that do
not interfere significantly with biological controllers. In
other cases, spraying specific sectors of the orchard help to
maintain the beneficial fauna. In the same way, the
establishments of reservoirs for biological controllers,
together with cultural practices such as the elimination of
low branches, removal of branches that constitute the
origin of infections, and the maintenance of vegetation that
feed beneficial fauna in adult stage, are also biological
control practices. Finally, the artificial introduction of
biological controls through the development and release
method can help where the beneficial fauna is not efficient
enough or does not colonize the orchard on time
(López-Laport 1999).