Celeriac 315
given as a basal dose and the remaining nitrogen is applied at 30 and 60 days after
transplanting.
17.2.6 Intercultural practices
Regular intercultural operations like thinning, hoeing and earthing-up should be
attended to. Any side shoots or suckers appearing should be removed promptly. The
surface of the soil should be loosened. It is done at frequent intervals to draw soil
away from the plants rather than upwards because the further they stand out of the
ground, the better. From mid-November onwards the scheme is altered and the soil
is drawn up towards the plant to give some protection.
17.2.7 Irrigation
Celeriac requires much water while growing. The first irrigation is given immediately
after planting or the roots may not attain best size and quality. Water should be given
before the first indication of wilting or any check to growth. It requires 2.5–4 cm of
water each week during dry periods. During dry weather, mulching will be helpful.
Black polythene sheeting has been found to retain moisture.
17.2.8 Pests and diseases
Celeriac is not seriously attacked by many insects and it is seldom that any of them
cause serious losses. However, under some conditions, the tarnished plant bug and
carrot rust fly cause considerable injury. The celery looper and the larva of the black
swallow-tail butterfly attack celeriac, but are seldom very injurious. They can easily
be controlled by available insecticides. Celeriac is susceptible to injury by several
diseases including late blight, early blight, phoma root rot, black heart and root knot.
Late blight is caused by Septoria apii and this organism attacks only celeriac and
celery. Small brown spots appear on the leaves, which later coalesce, and the entire
leaf may become dry. The early blight caused by Cercospora apii leads to small
circular yellowish brown spots, which enlarge rapidly to dark brown, surrounded by
a band of yellow. Both the diseases could be controlled by soaking the seeds in hot
water for 25 minutes or in formaldehyde solution for 30 minutes or in mercuric
chloride solution for 20 minutes following a half-hour soak in lukewarm water to
soften the fungus.
Phoma root rot caused by Phoma apiicola and leads to wilting and dropping of
leaves. Crop rotation, burning refuse, guarding against seedbed infection and destruction
of infected seedlings are recommended. Black heart is a physiological disorder that
is first seen as tip burn in younger leaves and quickly spreads to all of the young
foliage. Hot weather and excessive moisture leads to this disorder. Root knot is
caused by a nematode, Heterodea radicicola, which leads to deformed roots, unfit for
consumption. Steam sterilization of the seed bed before sowing will effectively control
nematode infestation.
17.2.9 Harvesting
Celeriac attains its full flavour after it has received a frost. Harvestable maturity is
reached when the roots have attained a diameter of five centimetres. When fully