PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
PATH 372 Diseases of Horticultural Crops
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Gummed portions <strong>of</strong> affected bark should be removed and the cut surface<br />
protected.<br />
Spraying with 0.1% carbendazim on the affected limbs and forks is useful to<br />
restrict the disease spread.<br />
3) Dry root rot: Fungal complex (Fusarium sp., Diplodia natalensis and<br />
Macrophomina phaseolina)<br />
Economic Importance: Dry root rot is a major problem in all citrus growing areas <strong>of</strong><br />
Andhra Paradesh in both sweet orange and acid lime. It is also common in North<br />
Arcot district in Tamil Nadu and in Mandarins in Wynad<br />
Symptoms:<br />
The disease is characterized by moist decay <strong>of</strong> root bark in the early stages. Later,<br />
the bark becomes dry and shredded with hard dead wood underneath.<br />
The affected trees show yellowing <strong>of</strong> foliage and bare necks.<br />
The flowering is increased and the affected trees bear a heavy crop <strong>of</strong> small sized<br />
fruits. The affected roots emit a foul odour and the tree finally dies.<br />
Peeling <strong>of</strong> bark <strong>of</strong> the affected roots and formation <strong>of</strong> black sclerotia on the root<br />
surface is also common<br />
Favourable conditions<br />
Excessive moisture, direct contact <strong>of</strong> water with trunk, poor aeration, heavy soils, and<br />
frequent injuries to roots, excessive manuring at long intervals and close planting<br />
favour dry root incidence. Lack <strong>of</strong> sufficient moisture or inadequate supply <strong>of</strong><br />
nitrogen may also lead to this disease. Defective soil, hard pan formation below the<br />
second foot and unfavourable soil-air-moisture relationship in the subsoil leads to<br />
inadequate oxygen at root zone which is primarily responsible for the incidence <strong>of</strong> dry<br />
root rot.<br />
Management:<br />
Cut and destroy the diseased roots, if only one or two roots are affected and the<br />
tap root and crown are still in good condition. The cut surface should be protected<br />
with Bordeaux paste.<br />
Avoid deep ploughing or digging which are likely to injure roots<br />
Leaf mulch in the tree basins during the dry season helps in conserving the soil<br />
moisture and thereby reduces disease incidence<br />
Spray with Urea (4.5 kg in 450 litres <strong>of</strong> water) to reduce disease intensity<br />
Drench the soil with 0.25 carbendazim + 0.25% Mancozeb at the rate <strong>of</strong> 1 litre per<br />
m 2 <strong>of</strong> the tree basin in early stage <strong>of</strong> infection<br />
Apply 10 kg <strong>of</strong> neem cake followed by soil drenching with 0.5% Trichoderma<br />
viride formulation + 0.2% copper oxy chloride in the early stages <strong>of</strong> infection<br />
4) Scab / Verucosis: Elsinoe fawcetti (I.S: Sphaceloma fawcetti)<br />
Economic Importance: In India this disease is reported from Bengal, Punjab, Assam,<br />
Karnataka, Uttar Pradesh and Andhra Pradesh. It is one <strong>of</strong> the common diseases <strong>of</strong><br />
sour oranges, rough lemon, tangelos and Pummelo. In Andhra Pradesh it is severe on<br />
Rangapur lime. The sweet oranges are mostly resistant to the disease.<br />
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