Annona Species Monograph.pdf - Crops for the Future

Chapter 10. Agronomy
soursop, custard apple, sugar apple and on related species, e.g., A.
diversifolia (Weber, 1973).
Anthracnose (Colletotrichum gloeosporioides) is a cosmopolitan disease
attacking all annonas. This disease is responsible for 90% of the preharvest
loss of soursop fruits in Bahia, Brazil (Nieto-Angel, 1999). In Bahia,
predisposing climatic conditions for anthracnose attacks are highly
favourable, due to high rainfall and atmospheric humidity, and during wet
seasons in dry areas (Dhingra et al., 1980). In Mexico, the incidence of
anthracnose in cherimoya varies from 50 to 70%, although mainly in
orchards without adequate control (Rebollar-Alviter et al., 1997). This
disease causes twig dieback, defoliation and dropping of flowers and fruit,
while in mature fruit its infection causes black lesions (Nakasone and Paull,
1998). Management and control of anthracnose involves a thorough cleanup
at the end of the dry season, including the pruning of infected twigs, removal
of rotting fruits on the ground, and then burning of all waste. Spraying with
the fungicide benomyl 0.06%, intercalated with copper oxychloride 0.15%,
every week during the rainy season and every three weeks during the dry
season, gives adequate control (Junqueira et al., 1996). In India, Singh (1992)
recommended spraying with 0.05% benomyl or 0.2% mancozeb M43 at 15-
20 day intervals.
Black canker (Phomopsis spp.), diplodia rot (Botryodiplodia theobromae)
and purple blotch (Phytophthora palmivora) are fungal diseases attacking the
fruits (George and Nissen, 1980; Agustín and Alviter, 1996; Nakasone and
Paull, 1998). Black canker and diplodia rot occur mainly in neglected
orchards; they show similar symptoms of purplish to black spots or blotches
confined to the surface of the fruit. Diplodia rot is distinguished by its darker
internal discolouration and the extensive corky rotting it produces. Diplodia
rot has also been described by Junqueira et al. (1996) as attacking the
junctions between rootstocks and scions of soursop, ultimately killing the
plant. Purple blotch is distinguished by small spots on immature fruits that
expand until most of the fruit surface is affected (George and Nissen, 1980).
There are several management systems to control these diseases, most of
which should be applied preventively: a) pruning the low branches to avoid
high humidity under the canopy and brushing with 1% paste of copper
oxychloride; b) keeping the plants in a good nutritional state; c) avoiding
physical damage to the fruits, as well as keeping adequate control of fruit and
seed borers; d) brushing the graft junction with 4% copper oxychloride paste;
e) spraying with benomyl 0.2%, every 15-20 days during the rainy season
(Junqueira et al., 1996; Kavati et al., 1997; SPT-TCA, 1999).
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