Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
starches). Thermophilic bacteria break down proteins, fats, cellulose, hemicelluloses.
Psychrophiles are aerobic bacteria that thrive in low temperatures of approximately 55 degrees
Fahrenheit and slowly decompose compost even at 0 degrees Fahrenheit.
Actinomycetes the second major group present in compost, are filamentous bacteria
without nuclei, but they grow multicellular filaments like fungi. Actinomycetes form long, thread-like
branched filaments that look like gray spider webs stretching throughout compost, and give the
pile a pleasing earthy smell. In composting they play an important role in degrading complex
organics such as cellulose, lignin, chitin, and proteins. Their enzymes enable them to chemically
breakdown tough woody materials.
The third major group of microorganisms present in compost is fungi that include molds
and yeasts. Most fungi are classified as saprophytes because they obtain nutrients from dead
plant matter. In compost, fungi are important because they break down tough debris, enabling
bacteria to continue the decomposition process once most of the cellulose has been exhausted.
Fungi species are numerous during both mesophilic and thermophilic phases of composting.
Including all these microbes, earthworm, millipedes, nematodes and protozoa also play
important role in composting. Earthworms play an important role in breaking down organic
materials and stabilizing vermi compost. They are constantly tunneling and feeding on dead plants
and decaying insects during the daylight hours. Their tunneling aerates the compost and enables
water, nutrients and oxygen to filter down. They coat organic materials with a mucus-like film that
binds small particles together and protect nutrients from leaching.
Compost and Disease Management
Composts have long been known to improve soil fertility and plant diseases management.
Previously it has been shown that components of composts improve the ability of plants to resist
disease caused by root pathogen like Fusarium, Phytophthora, Pythium, Rhizoctonia etc. and
foliar pathogens like Pseudomonas, Colletotrichum, Xanthomonas etc.
Among soil borne root pathogen, suppression of Fusarium using composts has been
reported by several researchers (Punja et al., 2002). The severity of various diseases caused by
Fusarium has been reduced between 20- 90% using compost amendments. Microbial activity has
been considered a key factor in suppression of Fusarium wilt. Composts increased microbial
populations and microbial activity in composts and composted peat mixes increased by 50%
(Cotxarrera et al., 2002). Several microorganisms or biocontrol agents have been isolated from
composts or shown to contribute to suppression of Fusarium spp. including populations of nonpathogenic
strains of Fusarium oxysporum and fluorescent Pseudomonas spp. (Kannangara et al.,
2000); Trichoderma and Flavobacterum (Hoitink and Fahy, 1986).
Phytophthora is another soil-borne pathogenic fungus that causes a variety of problems
including root rot, a form of “dieback”; crown rot; or Phytophthora blight of plants. Composts have
been used successfully for suppression of Phytophthora crown and root rots of nursery and fruit
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