STUDIES ON RESISTANCE TO INSECTICIDES IN Spodoptera litura (Fabricius) ON GROUNDNUT
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Date
1999
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University of Agricultural Sciences, Dharwad
Abstract
Irrespective of the insecticides, maximum loss of sensitivity was observed
in Manvi strain (39.09% mortality) followed by Hospet (68.48%) strain which
represented high pesticide usage areas. Whereas strains from low pesticide pressured
areas were highly sensitive with more than 80.00 percent larval mortality. Irrespective
of the strains, maximum loss of sensitivity was for monocrotophos (65.56%) followed
by carbaryl (68.89%).
Resistance to monocrotophos was highest (8.48 folds) followed by endosulfan
(3.30), quinalphos (2.00) and cypermethrin (1.61). Higher levels of resistance,
irrespective of the insecticides was noticed from medium (3.80-9.79) and high (4.08-
5.07) pesticide usage areas.
The dynamics of resistance to monocrotophos was static from September
to February (33.1 2 - 37.66 folds) except during October (44.99). Later the resistance
build-up was fast, reaching a peak of 93.1 1 folds during April.
Sesame oil, honge oil and pundi oil exhibited higher synergistic action with
synergistic ratios of 14.32, 11.97 and 10.85 for cypermethrin and 3.32, 2.84 and
3.41 for monocrotophos, respectively.
The pathogenisity of microbial agents, Viz., Spodoptera litura nuclear
polyhedrosis virus. Bacillus thuringiensis sub sp. kurstaki and Nomuraea rileyi to
susceptible and resistant strains of S.litura remained same. B.thuringiensis and SI
NPV were more effective against resistant populations of S.litura by causing 74 and
72 percent larval mortality, respectively compared to quinalphos (60%). N. rileyi
was least effective with 34.00 percent larval mortality.
Among the new molecules of insecticides tested, polytrin C-44, profenofos
and carbosulfan were highly effective causing more than 96 percent larval mortality;
whereas cypermethrin was totally ineffective without causing any mortality followed
by monocrotophos which caused only 20.00 percent mortality.
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No . of references 104