Annona Species Monograph.pdf - Crops for the Future

Chapter 10. Agronomy
north-eastern states of Brazil, while cercosporiose attacks under the lower
temperatures and dry conditions of Brazil's central region. Spraying with
copper oxychloride gives adequate control of these diseases (Junqueira et al.,
1996).
Nematodes of different species, such as Helicotylenchus spp., Meloidogyne
incognita, Macroposthonia spp., Tylenchorhynchus phaseoli and Xiphinema
spp. have been described as attacking cherimoya, soursop and sugar apple
(Sharma, 1973; Sharma, 1977; Monteiro et al., 1978; Ferraz et al., 1989). In
Brazil, the disease called soursop decline has been associated with the attack
of nematodes of the Gracilacus species in Ceará State, north-eastern region,
and in Brasilia (Sharma et al., 1985; Freire and Cardoso, 1997).
10.3.8 Physiological disorders
Annona fruits occasionally present abnormalities that are not due to diseases
or insect pests, but are due to physiological disorders. George et al. (1987)
described some of them as follows:
Fruit splitting - probably caused by sudden changes in fruit moisture content
or temperature, and some species and varieties appear to be less susceptible
than others.
Russeting - superficial russeting of the fruit skin. The combination of low
night temperatures (lower than 13°C) accompanied by low humidity is the
probable main cause. Nearly mature fruits are more susceptible, and
cherimoya is less susceptible than sugar apple and their hybrid atemoya.
Crocodile skin - Fruits show wavy and pointed carpels. Extremely vigorous
plants show more severe symptoms. No hypotheses of cause have been
advanced.
Hard seed casing and brown lumps - There is a suspicion that boron
deficiency or sudden changes in fruit water content may be the main causes
of this physiological disorder. In north-eastern Brazil, pulp of sugar apple
fruit commonly shows hard seed casing disorder when trees are cultivated in
dry areas without irrigation.
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