Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
solarization has been demonstrated (Stapleton and DeVay, 1982).
Limitations
Solarization involves limitations, difficulties and possible negative effects.
It is weather dependent and can only be used in regions where the climate is suitable (hot) and
the soil is free of crops for about one month or more at a time of tarping with PE sheets. The
soil heating effect may be limited on cloudy days. Wind or air movement across the plastic
sheet rapidly dissipates the trapped heat. Strong winds may also lift or tear the sheets.
It is too expensive for some crops and ineffective in the control of certain diseases
Heat tolerant pathogens might develop after repeated application, though selection for
tolerance to lethal agents is not likely to develop with disinfestation methods which are not
target specific
Another possibility would be an increase in pathogen population due to a harmful effect on its
antagonists
Future Thrust
Economics: The economic profitability of disease control depends on the additional income
obtained and the cost of application. The additional income obtained through solarization far
exceeds with high-value crops but with other crops situation may not be the same. There are
several possibilities for reducing the cost of mulching: (a) Used polyethylene may be as effective
as the new, thus reducing the cost to nearly zero (b) Reusing the polyethylene, providing it is
durable (c) If required during the growing season, durable sheets may be used for both
solarization and mulch (d) The production of thinner polythene sheets (of an adequate strength)
will reduce the amount needed per hectare.
Development in plastic technology: Developments in this field may provide improved and
economical mulching materials with greater heating efficiency and increased durability. This may
include 1) Biodegradable plastic that decomposes in the natural environment 2) Further
development of polyethylene recycling processes 3) Developing economic, novel plastic or other
materials more efficient than polythene in trapping solar energy, thus reducing our dependence on
climate and making this available to cooler regions 4) Possibility of plastic material that can be
sprayed on the soil, instead of polyethylene mulching, should be explored. At present,
biodegradable plastic products available in the market are more expensive than traditional plastics.
Their cost needs to be reduced to make them economical.
REFERENCES
• Abdel Rahim, M. F., Satour, M. M., Mickail, K.Y. and El Eraki, S. A. (1988). Effectiveness of soil
solarization in furrow irrigated Egyptian soils. Plant Dis.. 72: 143-146.
• Barbercheck, M.E.and von Broembsen, S.L (1986). Effect of soil solarization on plant parasitic
nematodes and Phytophthora cinnamomi in South Africa.Plant Dis. 70:945-950.
• Broadbent, P, Baker, KF, Franks, N and Holland, J. 1977. Effect of Bacillus spp. on increased
growth of seedlings in steamed and in non treated soil. Phytopathology. 67: 1027-
1034.
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