Citrus - Crop Post-Harvest: Science and Technology - page 72

Effective control of P. digitatum and P. italicum was also
seen by Nunes et al . (2007) during curing of Valencia
oranges.
Effective sanitation practices during pre- and post-
harvest handling can greatly reduce the incidence of
decay. Separation of sound fruit from the decayed ones in
storage or distribution or repack centres reduces possible
sources of inoculum and prevents contamination
(Wardowski & Brown 2001). Gaseous ozone treatments
in storage rooms can also decrease the load of inoculum
and inhibit the surface growth of mould on packages,
walls and floors. This will result in a reduction in the
amount of inoculum available for re-infections of stored
products (Renzo et al . 2005). Other physical treatments,
such as ultraviolet-C irradiation and heat treatment, using
hot-water dips or hot air curing, separately, or in combi-
nation, also reduced P. digitatum and P. italicum
(D'Hallewin et al . 2005; Ben Yehoshua et al . 2005).
A low dosage of ultraviolet-C light treatment on its own
can also control green mould when fruit is treated on its
stem end (Stevens et al . 2005). These physical control
strategies are considered a potential additional tool in the
decay control of citrus fruit in combination with current
fungicides.

CITRUS HANDLING PRACTICES

Harvesting
Citrus fruit are manually harvested by means of
snap-picking (Kruger & Penter 2006). In certain coun-
tries, trunk shakers and abscission chemicals are used
(Mukhopadhyay 2004). Injuries that occur during harvest-
ing and transportation of the fruit to the pack house pro-
vide entry sites for wound pathogens that cause green or
blue mould and sour rot. Nail inspections prior to harvest-
ing are therefore practiced in some countries and may
contribute to reduce wounding and decay. Once picked,
the fruit is placed into picking bags and moved to central-
ised collection areas in the orchard. Once filled, the pick-
ing bag is usually carried to a central point in the orchard
and emptied out into large wooden crates, plastic bins or
trailers before being transported to an on- or off-farm
packing facility (Timmer & Duncan 1999). Adequate
awareness about careful picking practices will reduce
damage to fruit during harvesting, off-loading, transport
and packing. In general fruit are not harvested when wet,
since the moisture on the fruit surface may favour post-
harvest infections (Agrios 2005).

Good agricultural practices
Basic good agricultural practices (GAP) include a variety
of well-known systems that should be implemented effec-
tively and audited for compliance to one or other of the
required voluntary standards. Management commitment
and continual training and inspection often provide an
effective framework for GAP. Some examples of GAP
include the following:

Integrated control options and strategies
Although there is no doubt that biopesticides provide for
an effective alternative control strategy, they do not always
give consistent results and are often less effective compared
with commercial fungicides (Janisiewicz et al . 1992;
El-Ghaouth et al . 2002; Leverentz et al . 2003). Therefore, to
achieve a similar level of efficacy provided by conven-
tional chemicals, the use of microbial antagonists integrated
with commercial chemicals (Korsten 1993; Droby et al .
1998; Kienay et al . 2005; Stockwell & Stack 2007), hot
water (Korsten et al . 1991; Pusey 1994; Auret 2000;
Nunes et al . 2002; Palou et al . 2002; Obagwu & Korsten
2003; Kienay et al . 2005), chloride salts (McLaughlin
et al . 1990; Wisniewski et al . 1995), carbonate salts
(Smilanick et al . 1999; El-Ghaouth et al . 2000b; Palou
et al . 2001, 2002; Obagwu & Korsten 2003; Smilanick
et al . 2005) and/or natural plant extracts (Vaugh et al .
1993; Mattheis & Roberts 1993; Wilson et al . 1997;
Obagwu et al . 1997; Obagwu 2003) and other physical
treatments such as curing and heat treatments (Leverentz
et al . 2000; Ikediala et al . 2002; Plaza et al . 2003; Kinay
et al . 2005; Smilanick et al . 2006; Zhang & Swingle 2005)
provide a potential effective alternative disease control
strategy. In most countries, an integrated disease control
strategy is followed for citrus.

• Effective orchard hygiene practices include removal of
infected fruit in or under the tree to prevent build-up of
pathogen inoculum levels.
• Best hand harvesting practices include gentle handling of
the product to prevent bruising and wounding.
• Citrus fruit handlers should also maintain short clean
nails to prevent bruising and nail inspections prior to
picking and packing is standard practice in some
countries.
• The effective implementation of good personal hygiene
practices by workers includes continual training and
awareness campaigns and the provision of adequate
ablution and hand washing facilities.
• A general good harvesting principle is to avoid direct
fruit - soil contact, because the particles may cause abra-
sive injuries during fruit handling and negatively affect
the efficacy of chlorine wash treatments.