Post harvest diseases fruits and vegetables - Xavier University ...

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Postharvest Disease Summary 305
within the range of 10-25°C. Ascospore germination and germ-tube
elongation rise with the increasing temperatures, from 7 to 15°C (Hong
and Michaihdes, 1998). Reduction in ascospore discharge at higher
temperatures (up to 25°C) is due to the faster disintegration of apothecia.
However, high temperatures can also expedite drying of the apothecia in
orchards when air humidity is low. Such information may help in the
development of warning systems and in scheduling fungicide application
against brown rot infection.
Following invasion of apricot flower parts, the fungus may progress
into young fruits, where infection remains quiescent until the fruit ripens
(Wade and Cruickshank, 1992). Quiescent visible infections of
M. fructicola have been described on plums (Northover and Cerkauskas,
1994), whereas symptomless latent infections were reported on cherries
(Adaskaveg et al., 2000). Additional infection may occur while the fruits
are maturing via stomata, via hair sockets in peaches (Hall, 1971) or
directly through the skin. However, the most common mode of invasion is
through preharvest wounds caused by insects, hail or other adverse
weather, or via injuries sustained during harvest and postharvest
handling.
Decay is characteristically firm (Byrde et al., 1973). In advanced
stages, spore masses, which are often arranged in concentric rings, cover
the surface of the affected area. Within a few days at room temperature,
the entire fruit may be decayed. Brown rot can spread rapidly by contact
infection, forming 'nesting' during storage and marketing.
B. Botrytis cinerea Pers. [perfect state: Botryotinia fuckeliana (de
Bary) Whetzel]
This fungus is one of the major pathogens of stone fruits in all
producing areas. It survives as sclerotia in the soil or on dead plant
material. During cool weather the fungus sporulates and inoculum for
infection may be readily available. Infection may be initiated
throughout the growing season under natural orchard conditions.
Fourie and Holz (1994) indicated that B, cinerea does not penetrate
young nectarine and plum fruits via floral parts to establish latent
infections as in pears and apples (DeKock and Holz, 1991; Tronsmo and
Raa, 1977), strawberries and raspberries (Powelson, 1960; Dashwood
and Fox, 1988), grapes (McClellan and Hewitt, 1973) and cucumbers
(Elad, 1988); in nectarines and plums the pathogen is likely to be
introduced by field infection of developing fruit. Conidia germinate in
water on the surfaces of both green and mature fruits, and the germ
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