Page 8 - AWA Vol.36-No.5

CROP PROTECTION

ing in final positions in the field. Cashew caused by highly toxic cashew oil which
seeds have a notoriously poor germina- is contained in the freshly harvested
tion rate which means 2–3 seeds should nuts. Farmers and others must not at-
be sown per planting hole and subse- tempt to break open cashew nuts (fruit)
quently thinned out as necessary. Thin- straight after harvesting because the
ning should leave seedlings at a final kernel (seed) inside contains toxic oil.
minimal spacing of 12 m between plants If touched this oil is capable of causing
in the row and another 12 m between an itchy rash of the skin and moreover
rows. Some plantations prefer a wider painful blisters in the mouth if the con-
spacing up to 15 m x 15 m. tents of fresh cashew nuts are eaten. Ca-
Young growing trees should be irri- shew nuts must be dried for several
gated to assist establishment but mature days and then roasted before being
trees can survive dry periods because cracked open.
of the tree’s intrinsically extensive root
systems which is able to access moisture
from deep in the soil profile. Cashew re-
quires about 750 mm rain per annum but
its ability to tolerate over an extended
dry period (up to 6 months) is facilitat-
During reproductive ed by the trees wide-ranging root sys-
development the cashew nut tem. However, this ability to withstand
(true fruit) reaches its full size drought may be lost if trees are planted
long before the cashew apple too close together.
(receptacle or accessory
fruit) has grown to reach full A weed free area should be main-
dimensions tained around the base of the tree trunk
to prevent competition for both water
other fruit trees will not survive. As such and nutrients especially when trees are
cashew is entirely suitable for soil ero- young and not completely established.
sion control project plantings along Cashews require minimal pruning which
coastal areas. should be restricted to removal of those
branches which may impede the move-
Cashew has traditionally been prop-
agated from mature seeds which are ment and use of machinery in commer-
cial plantations and only carried out
sown directly into the final planting po- once the tree is 6 years old. Cashew has a spreading tree
sition or into seed beds or polybags in a canopy with some branches
nursery with well-grown seedlings used Harvesting and use of cashew nuts re- quite close to the ground, thus
for transplanting. Suitability of seeds quires a meticulous operation to avoid putting flowers and fruit within
for sowing can be gauged by immers- severe body reaction and poisoning easy reach of fast growing
ing in water with only those which sink tropical weeds like the grass
being selected for sowing. Cashew can shown here.
be propagated from stem cuttings and
significant increases in yield can be ob- Anthracnose disease
tained by selecting seed for high yield follows the cashew tree
and then propagating these selections
by cuttings. Tropical tree crops typically suffer a
More recently plant breeding estab- range of diseases which affect leaves,
lishments around the world and notably fruit, branches, trunks and roots, and ca-
the Kerala Agricultural University (KAU) shew is no exception. However, as with
in southern India have produced a range other tropical fruit tree crops, including
of modern, high- yielding varieties in- mango, avocado and citrus some dis-
cluding ‘Priyanka’ and ‘Amrutha’ among eases have managed to follow the dis-
the most recent from KAU. Benefits in- semination and distribution of cashew
clude early flowering, good response to from its New World roots and into trop-
fertilizer and nutrient application and ics-wide commercial crops. In the case
the production of large, high-grade ca- of cashew the pathogen is the fungus
shew nuts. These varieties are propa- Colletotrichum gloeosporioides which
gated by soft-wood grafting. causes a disease commonly called an-
thracnose.
Newly emerged tree seedlings should Ripe and mature cashew nut
be grown on under a shade level of ap- inserted in the full-size, rose- Anthracnose is the most widespread
proximately 50 per cent and then hard- coloured cashew apple and damaging disease of cashew. Wher-
ened off in direct sunlight prior to plant- ever cashew is grown this disease is a
6 Vol. 36 No. 5

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