Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Soft wood/Wedge grafting
When the seedling attains pencil thickness, it is ready for grafting. The top of the rootstock
is cut off at the height of 15-18 cm from the surface of poly bag or ground. Splitting the be headed
rootstock vertically down the center, to a point 4 to 5 cm below the cut surface. Scion stick is
collected from desired variety. The shoot with 6 to 8 healthy buds, 12 to 18 cm long pencil thick is
cut from the selected mother plant. Scion stick should be cut from both sides into a tapering wedge
approximately 4 to 5 cm long. The tapered end is inserted into the split stem of the rootstock. The
rootstock and scion are wrapped tightly with 2 cm wide and 25 to 30 cm in length polyethylene
strip. Immediately after grafting, the scion is covered with poly cap. Within 12 to 15 days of grafting
scion shoots sprout, which is visible from outside. The poly caps are carefully removed after 21
days and these are kept for hardening. Early removal of poly caps results in high mortality. Winter
months suitable for wedge grafting in the field conditions, while round the year can be grafted in
greenhouse. Field transferable grafts become ready within 6-8 months of seed sowing.
Good Nursery Practices to Raise Disease - Free
Plants of Citrus
NRC for Citrus, Nagpur has taken a mission oriented programme on production of disease
free planting material of Nagpur mandarin, acid lime and sweet orange (Mosambi) by adopting the
most advanced and internationally accepted techniques of nursery management duly standardized
at the Centre (Singh et al.) The disease free (from virus and fungal diseases) plants were raised to
supply to Government owned nurseries for raising mother plants and to the citrus growers to
overcome the problem of citrus decline. The techniques adopted in production of disease free
planting material are briefed here (Singh, 1999).
Containerised Nursery System
In India most of the citrus nurseries are grown as field nursery. In field nurseries, the
eradication of soil borne pathogens like Phytophthora once introduced becomes very difficult. To
avoid this problem, concept of containerized nursery system was adopted. The infrastructure
required for such nurseries includes shade net houses (50 % shade), sterilized plastic trays, UV
stabilized black poly bags (100 μ), UV stabilized transparent polythene for solarization, fumigation
of potting mixture, a separate set of nursery equipments etc.
Potting mixture: The potting mixture, consisting one part of virgin fertile soil + sand +FYM
(sterilized), was used in plastic trays for seed sowing in primary nursery. The same sterilized
mixture was used for filling the polybags to be used in secondary nursery.
A. Soil Solarization: The potting mixture was first collected on a concrete floor and spread in the
form of flat bed of 1.5’ thick layer. These beds were completely drenched with water before
covering it with 100 μ UV stabilized transparent polythene sheets in summer months (April- May)
when atmospheric temperature goes up to 45 – 46 0 C. The edges of polythene sheet were
completely sealed with soil to avoid vapour loss, which allowed the inside temperature to rise upto
54 o C. Soil solarization was done for 4 – 6 weeks.
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