Epidemiology and Ecofriendly Management of Pigeonpea Wilt
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Date
2012
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Abstract
Wilt of Pigeonpea (Cajanus cajan (L) Millisp.) incited by Fusarium udum (Butler) is a serious threat to the production and productivity of this crop in India and abroad. In Bihar, 18.3 per cent average incidence of wilt has been reported. Effect of soil texture on wilt incidence revealed maximum wilt incidence of 74.75 per cent in loam soil and least in clay soil (49.50%). The effect of soil pH on disease indicated maximum wilt incidence (51.50 %) at soil pH 5 followed by pH 7 (47.25%). Correlation coefficient between wilt incidence and pH of the soil revealed that wilt incidence was negatively (-0.960*) and significantly correlated with soil pH.
Disease appearance was early i.e. 19 days at highest inoculum load of 30 g/kg soil where the mean population of F. udum was 12.92 x 103 cfu/g soil and wilt incidence was also highest 70.25 per cent after 30 days of inoculation. The inoculum load of F. udum @ 20 g/kg soil was the optimum inoculum load of for creation of disease epiphytotic as the wilt incidence appeared in 20 and 30 g inoculum load did not differ significantly. Correlation between inoculum density of F. udum (cfu/g soil) and days of disease appearance showed significant and negative correlation and ‘r’ value -0.890* and -0.867* at 30 and 60 days after sowing. Whereas wilt incidence was significantly and positively correlated with inoculum density and ‘r’ values were 0.920* and 0.898* at 30 and 60 days after sowing respectively. The mean values of coefficient of determination (R2), indicated that 85 and 81.0 per cent variation in wilt incidence at 30 and 60 DAS respectively were contributed by inoculum density. It is, therefore, concluded that wilt incidence mainly depended on the initial population of F. udum.
Significantly maximum population of F. udum (4.83 x 103 cfu/g soil) was recorded in 1st July and 16th July sowing at upper (0-15) soil strata followed by the subsequent date of sowing on same depth of soil strata. At crop harvest stage maximum population of F. udum 15.17 x 103 cfu/g soil in 1st July sowing in upper soil strata (0-15 cm). The minimum population of F. udum was recorded in 16th August sowing at 31-45 cm soil strata.
Sowing of pigeonpea in first fortnight recorded maximum wilt incidence 89.58 % in 1st July sowing which was at par with 16th July sowing (86.83 %) and significantly higher than August sowing.
Correlation coefficient (r) between the wilt incidence and weather factors in pigeonpea cultivar ICP 2376 showed a negative and significant correlation between disease incidence and minimum temperature (0C), soil moisture (%), rainfall (mm) and number of rainy days and observed ‘r’ values were -0.591*, -0.987**, -0.593** and -0.664*, respectively whereas it was non significant with R.H at 7hrs (-0.223) and 14hrs (-0.527). Maximum temperature and soil temperature had negative and non significant correlation and observed ‘r’ values were lower i.e. 0.141 and 0.170, respectively. Population F. udum was positively (0.706**) and significantly correlated.
Best fitted equation for prediction of wilt disease on cultivar ICP 2376 is
Y8 =177.419+0.021(F. udum population) +0.308(Soil temp.0C)-6.347(Soil moisture %)
R2 = 0.980
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Keywords
Pigeonpea, Wilt, Ecofreindly management