BIO-FUMIGATION IN THE MANAGEMENT OF STEM AND POD ROT OF GROUNDNUT CAUSED BY Sclerotium rolfsii (Sacc.)
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Date
2011
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
Groundnut is one of the most important oilseed crops grown in Andhra
Pradesh. The crop is affected by variety of diseases, of which stem rot caused by
Sclerotium rolfsii is very important and has become one of the major constraints
causing damage to the crop. Management of stem rot is difficult because of soil
borne nature of the pathogen and its wide host range and the chemical methods are
very expensive and will not provide complete protection from the pathogen.
There is worldwide acceptance to the use of ecologically safe, environment
friendly methods of protecting crops from the plant pathogens. Using plant produced
allelochemicals in agricultural and horticultural practices could minimize synthetic
pesticide use, reduce the associated potential for environmental contamination and
contribute to a sustainable agricultural system.
In vitro studies conducted to reduce the growth of S. rolfsii against mustard
leaf discs (8 mm size) inoculated with S. rolfsii (5 mm size), un-inoculated leaf discs
revealed at the end of the experiment i. e. at 72 hours, the growth of the pathogen
exposed to S. rolfsii inoculated leaf discs was reduced by 15.68 per cent over control
and in un-inoculated leaf discs it recorded 11.48 per cent over control. Similarly, the
S. rolfsii exposed to mustard powder 2 mg, 5 mg, 10 mg and 20 mg after 24 hours of
exposure to mustard powder, the growth of S. rolfsii was completely inhibited in all
the concentrations. At the end of the experiment at 96 hours of exposure, mustard
powder of 20 mg was found 63.2% inhibitory to the growth of S. rolfsii, while 2 mg
of mustard powder did not show any effect on S. rolfsii, suggesting that the fungus
may have the ability to adapt to volatiles at lower concentrations.
In green house experiment, incorporation of the mustard plant parts into the
soil reduced the infectivity of S. rolfsii at every date at which inoculum was added to
soil over the 13 day period. The disease incidence was minimum 37.44% at 0 day
application of S. rolfsii immediately after incorporation of mustard. The present
results also showed that the persistence of Brassica residues was significantly shorter
than the persistence of residue action.
The results on the effect of incorporation of Brassica sp residues with other
treatments on stem and pod rot of groundnut, indicated that the incorporation of
mustard plant parts with conventional and non-conventional treatments highly
influenced the incidence of stem rot and plant growth. Treatment FYM application
@ 6 kg per plot + in situ application of Brassica residues + rhizobium seed treatment
@ 20 g per kg seed (T9) showed highest plant height (25.63, 36.93, 42.50 cm), leaf
area (272, 1040, 1348.58 cm2) at 30, 60 and 90 DAS respectively, fresh weight and
dry weight (70.91, 26.66 g plant1) and pod yield (2.16 kg plot-1) at the time of harvest.
Soil drenching with propiconazole @ 0.1% + in situ application of Brassica residues
@ 4 kg per plot + rhizobium seed treatment @ 20 g per kg seed (62.55%, 67.95%)
followed by soil solarization + in situ application of Brassica residues @ 4 kg per
plot + rhizobium seed treatment @ 20 g per kg seed (57.10%, 66.70%) resulted in
maximum reduction in stem rot and pod rot disease severity per cent over inoculated
control respectively. Among all the treatments lowest fungal and bacterial population
were recorded in soil drenching with propiconazole @ 0.1% + in situ application of Brassica
residues @ 4 kg per plot + rhizobium seed treatment @ 20 g per kg seed (before sowing of
groundnut as well as after harvest of groundnut (4.66 x 104, 5.00 x 104; 21.33 x105, 24.00 x
105 cfu g-1 of soil) respectively.
In vitro studies on the effect of dried leaf residues of mustard, cabbage and
onion on soil microbial population showed that the population of bacteria was
revealed more over the fungi in all the treatments. Minimum microbial population
was noticed in the soil exposed to dried mustard leaf volatiles followed by onion and
cabbage dried leaf residues
Description
Keywords
insecticides, cabbages, pesticides, plutella xylostella, inorganic acid salts, sampling, fruits, vegetables, land resources, yields, Sclerotium rolfsii (Sacc.)