SCREENING OF ROSE GENOTYPES AGAINST THRIPS, Scirtothrips dorsalis HOOD (THYSANOPTERA: THRIPIDAE) AND ITS MANAGEMENT
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Date
2015-06
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University of Horticultural Sciences, Bagalkot
Abstract
An investigations on screening of rose genotypes against incidence of
Scirtothrips dorsalis Hood under naturally ventilated polyhouse condition, identifying
resistant sources and efficacy of new molecules of insecticides against thrips were
undertaken during the year 2014-2015 at the Department of Entomology, College of
Horticulture, Bagalkot, Karnataka. Eleven genotypes were screened against thrips
under naturally ventilated polyhouse condition. Amongst them, Prettybride, Nobless,
Shakira, Bugati and Tropical were found to be superior by recording significantly
lesser level of thrips incidence. Whereas, Grandgala found to be inferior genotype by
recording higher level of thrips incidence as compared to other genotypes screened.
Further, categorization of rose genotypes based on their reaction to thrips incidence
on rose plants indicated that the Prettybride was categorised as highly resistant
genotype, Goldstrike, Shakira, Bugati, Avalench and Tineke as resistant genotypes,
Samurai, Tropical, Nobless and Bourdeux as susceptible and Grandgala as highly
susceptible genotype. Among different biophysical and biochemical traits identified
as sources of resistance to thrips, the genotypes categorised as highly resistant and
resistant had lesser leaf area, lesser leaf thickness, higher trichomes density, lighter
coloured flowers, moderate sized flowers, more flower compactness, lesser amount of
sugars and higher level of phenol contents as compared to the genotypes which were
categorized as susceptible and highly susceptible. The traits such as lesser leaf
thickness, lesser leaf area, lesser sugars and light coloured flowers are proved
important traits for breeding thrips resistant genotypes in future. Among the different
insecticides evaluated against thrips on rose in open field condition, Imidacloprid
30.50 SC (0.3 ml/L) and Diafenthiuron 50 WP (1 ml/L) were found to be superior
over the other chemicals in reducing the population of thrips and obtaining maximum
net returns as compared to other chemicals tested.