Field Efficacy of Viruses Infectious to the Cabbage Looper and Imported Cabbageworm on Late Cabbage12

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Abstract
Field plot tests in 4 consecutive years showed that efficacy of the nuclear polyhedrosis virus of the cabbage looper, Trichoplusia ni (Hübner), or the nuclear polyhedrosis virus of the alfalfa looper, Autographa californica (Speyer), (A.c. NPV) (7.5×1011 PIB/ha) equalled or surpassed the efficacy of formulations of Bacillus thuringiensis Berliner or chemical insecticide for control of the cabbage looper on late cabbage. Efficacy of preparations of A.c. NPV propagated in vitro compared favourably with that of in vivo preparations. The high efficacy of the granulosis virus of the imported cabbageworm, Pieris rapae (L.), against cabbageworm larvae also was demonstrated in these tests. Superior control of T. ni and P. rapae larvae was obtained by application of mixtures of the viruses with chemical insecticides or B. thuringiensis. Nosema necatrix (Kramer), a microsporidian, was an effective applied agent for control of T.ni larvae.