RESISTANCE STATUS AND GENETIC DIVERSITY OF Spodoptera litura (Fab.) AND INFLUENCE OF INTERCROPPING SYSTEMS ON INSECT PESTS IN SOYBEAN
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Date
2015-05
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University of Agricultural Sciences, Dharwad
Abstract
Investigation on genetic diversity, insecticide usage pattern, biochemical basis of
resistance, field resistance of Spodoptera litura and effect of intercropping system on
incidence of major insect pests in soybean was carried out at Institute of Agriculture
Biotechnology (IABT) and Main Agricultural Research Station (MARS), UAS, Dharwad during
2013-14 and 2014-15.
Random Amplified Polymorphic DNA (RAPD) analysis for genetic diversity of S. litura
larval population revealed, populations from Hyderabad and Indore, shared 100 per cent
similarity, Pune and Parbhani showed 90 per cent similarity, Adilabad and Hyderabad and
Adilabad and Indore showed 83 per cent similarity, Dharwad and Belagavi showed 72 per
cent similarity. The lowest genetic similarity value was observed between Dharwad and
Parbhani populations (46%).
Fourteen different insecticides were used by the farmers from various regions for
management of lepidopteran insect pests in soybean. Insecticides number used by the
farmers differed with region, in Parbhani-9, Adilabad and Hyderabad-8, Dharwad and
Belagavi-7 and Indore-5.
Prolonged and continuous usage of organophosphates, carbamates and pyrathriods
insecticides in soybean ecosystem resulted in increased activity of Car a- and b- esterase
and acetyl cholinesterase activity and elevated LC50 values, specified development of field
resistance in S. litura.
Intercropping system, soybean + pigeonpea (4:2) reduced the populations of soybean
defoliators (leaf folder, tobacco caterpillar, green semilooper), whereas soybean + cotton (2:1)
was more favorable for increase in natural enemies i.e., chrysopids, cadavars infestation by
N. rileyi and high incidence of predatory bugs.
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