PATH 372 Diseases of Horticultural Crops

Gummed portions of affected bark should be removed and the cut surface
protected.
Spraying with 0.1% carbendazim on the affected limbs and forks is useful to
restrict the disease spread.
3) Dry root rot: Fungal complex (Fusarium sp., Diplodia natalensis and
Macrophomina phaseolina)
Economic Importance: Dry root rot is a major problem in all citrus growing areas of
Andhra Paradesh in both sweet orange and acid lime. It is also common in North
Arcot district in Tamil Nadu and in Mandarins in Wynad
Symptoms:
The disease is characterized by moist decay of root bark in the early stages. Later,
the bark becomes dry and shredded with hard dead wood underneath.
The affected trees show yellowing of foliage and bare necks.
The flowering is increased and the affected trees bear a heavy crop of small sized
fruits. The affected roots emit a foul odour and the tree finally dies.
Peeling of bark of the affected roots and formation of black sclerotia on the root
surface is also common
Favourable conditions
Excessive moisture, direct contact of water with trunk, poor aeration, heavy soils, and
frequent injuries to roots, excessive manuring at long intervals and close planting
favour dry root incidence. Lack of sufficient moisture or inadequate supply of
nitrogen may also lead to this disease. Defective soil, hard pan formation below the
second foot and unfavourable soil-air-moisture relationship in the subsoil leads to
inadequate oxygen at root zone which is primarily responsible for the incidence of dry
root rot.
Management:
Cut and destroy the diseased roots, if only one or two roots are affected and the
tap root and crown are still in good condition. The cut surface should be protected
with Bordeaux paste.
Avoid deep ploughing or digging which are likely to injure roots
Leaf mulch in the tree basins during the dry season helps in conserving the soil
moisture and thereby reduces disease incidence
Spray with Urea (4.5 kg in 450 litres of water) to reduce disease intensity
Drench the soil with 0.25 carbendazim + 0.25% Mancozeb at the rate of 1 litre per
m 2 of the tree basin in early stage of infection
Apply 10 kg of neem cake followed by soil drenching with 0.5% Trichoderma
viride formulation + 0.2% copper oxy chloride in the early stages of infection
4) Scab / Verucosis: Elsinoe fawcetti (I.S: Sphaceloma fawcetti)
Economic Importance: In India this disease is reported from Bengal, Punjab, Assam,
Karnataka, Uttar Pradesh and Andhra Pradesh. It is one of the common diseases of
sour oranges, rough lemon, tangelos and Pummelo. In Andhra Pradesh it is severe on
Rangapur lime. The sweet oranges are mostly resistant to the disease.
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