Damage potential of tetranychus urticae koch and its management in cucumis sativus linnaeus
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Date
2013
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CCSHAU
Abstract
Studies on the seasonal incidence of Tetranychus urticae on cucumber revealed that mite attacked cucumber during summer months. Peak in T. urticae population was observed during first fortnight of August, 2011 (11.29 mites/sq cm leaf) and second fortnight of May, 2012 (9.71 mites/ sq cm leaf) under screen house conditions. Under field conditions, mite population peaked in the first week of August, 2011 (11.97 mites/ sq. cm leaf) and last week of May, 2012 (11.64 mites/ sq. cm leaf). Stage wise, grown up leaves harboured statistically higher number of mites as compared to tender and older leaves, both under screen house and field conditions. Among abiotic factors, T. urticae population showed positive correlation with maximum and minimum temperature, rainfall and wind
velocity and negative correlation with relative humidity under screen house conditions. Under field conditions, T. urticae population was positively correlated with wind velocity. During 2012, it was negatively correlated with relative humidity and positively with maximum temperature. Investigations were carried out to access the damage potential of T. urticae at different initial infestation densities. Among the parameters recorded, population build up of mite, number of chlorotic patches on cucumber leaves, reducing sugars and stress measures (proline and total phenols) significantly increased in proportion to initial inoculation level as compared to control. Additionally, fruit number, length, width and weight, photosynthetic pigments (total chlorophylls, Chlorophyll-a, b, carotenoids), total sugars, non reducing sugars and mineral content (nitrogen, potassium and phosphorus) significantly decreased in response to varying initial inoculums of T. urticae as compared to control during 60 day study period. Under field conditions, highest reduction in T. urticae population was achieved with Omite (0.05%) followed by Nimbecidine (5ml/l), B. bassiana (1010 spores ml-1), Withania (7.5%), B. bassiana
(108 spores ml-1), Liquorice (7.5%), Liquorice (5%), Liquorice (2.5%), Withania (5%) and Withania (2.5%). Higher yield of cucumber fruits was recorded in all the treatments as compared to control. In terms of percent increase in yield, omite caused highest increase (23.65% over control) followed by Nimbecidine, B. bassiana (1010 spores/ ml), Withania (7.5%), B. bassiana (108 spores/ ml), Liquorice (7.5%), Withania (5%), Liquorice (5%), Liquorice (2.5%), and Withania (2.5%) showing 13.97, 11.82, 10.75, 8.67, 8.67, 8.6, 6.76, 6.48 and 6.45 percent increase over control, respectively.
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Keywords
sorghum, fertilizers, soybeans, yields, planting, sowing, crops, application methods, farmyard manure, rhizobium