author(s)
K Chandrasekar, N Muthukrishnan and RP Soundararajan

abstract
In the habitat manipulation for enhancing natural enemy activity, different weed species were raised as strip crops in and around rice field (var.CO 51) to enhance predatory mirid bug, Cyrtorhinus lividipennis (Reuter) and to mitigate brown planthopper (BPH) Nilaparvata lugens (Stal). Echinochloa colonum (L.), Echinochloa crusgalli (L), Cyperus difformis (L.), Ammannia baccifera (L.), Eclipta alba (L) and Marsilea quadrifolia (L) were used as strip crops. The attraction of C. lividipennis towards different leaf and flower sample of strip crops were also studied through eight-armed olfactometer under laboratory assays. Results revealed that the mean population of mirid bugs and BPH on rice crop varied from 2.86 to 5.71and 1.86 to 5.29 nymphs and adults per hill due to strip crops. Rice + E. colonum strip cropping system significantly increases populations of C. lividipennis on rice (5.71/hill) along with highest occurrence ratio (0.68), minimum population of BPH (1.86/tiller) and more CB ratio (1:1.44). This was followed by rice + E. crusgalli, rice + C. difformis and rice + A. baccifera strip cropping systems that effected for the mean population of 5.29, 4.57 and 4.29 mirid bugs per hill on rice respectively. Rice + E. alba strip cropping system however caused for the population of 3.57 mirid bugs per hill on rice, when compared to the mirid population of 2.86 per hill on rice alone. Similarly, population of mirid bugs on strip crops ranged from 1.29 to 3.86 per hill. Maximum mirid bug population (3.86/plant) was observed on E. colonum strip crop. E. crusgalli and C. difformis registered 3.48 and 2.00 mirid bugs per plant respectively. A. baccifera, E. alba and M. quadrifolia had mirid populations of 1.71, 1.43 and 1.29 per plant. This study concluded that E. colonum and E. crusgalli can be used as strip crops in rice ecosystem to enhance the availability of mirid bugs. In olfactometer studies, mirid bug attraction was higher towards E. crusgalli leaf (3.13) and flower (2.94).