Use of a Fluorescent Brightener to Improve Pseudoplusia includens (Lepidoptera: Noctuidae) Nuclear Polyhedrosis Virus Activity in the Laboratory and Field

Abstract

A fluorescent brightener, Calcofluor white M2R, was studied for enhancement of Pseudoplusia includens (Walker), soybean looper, nuclear polyhedrosis virus (PiNPV) activity against P. includens larvae on semisynthetic diet, cotton, and soybean leaves and in field tests on soybean. Addition of 0.1% brightener to the PiNPV suspension on semisynthetic diet reduced the LC50 from 970 polyhedral inclusion bodies (PIB)/mm2 to 0.0625 PIB/mm2 for 2nd instars. The brightener (0.08%) reduced the LT50 of PiNPV from 15.9 to 6.4 d. In a spray table test, percentage mortality from virus of 2nd instars fed cotton leaves sprayed with 1 X 106 PIB/ml of PiNPV alone was significantly increased with the addition of 0.1% (soybean leaves only) and 1% brightener (cotton and soybean leaves). In a field test on artificially infested soybean plants, mortality from virus of 2nd to 4th instars was significantly increased by addition of 0.1% and 1.0% brightener. A field test on a natural population of P includens larvae of mixed ages showed that 0.3% and 1.0% brightener significantly enhanced mortality from virus of PiNPV-treated larvae. All tests demonstrated that a fluorescent brightener enhanced activity of PiNPV.