VARIETAL SUSCEPTIBILITY AND EVALUATION OF INSECTICIDES AGAINST POD-BORER COMPLEX ON PIGEONPEA Cajanus cajan (L.) Millsp.
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Date
1988
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AAU, Anand
Abstract
The relative bio-efficacy of fenvalerate E. C. formulation at 0.005%, 0.01% and 0.02% concentrations and 0.4% dust @ 25 kg/ha along with other synthetic pyrethroids viz., cypermethrin 0. 006%, decamethrin 0.0015% and fenvalerate [Sumicidin (R)] 0.01% as well as conventional insecticides viz. , endosulfan 0.07%, monocrotophos 0.04%, quinalphos 0.05% and 1.5% dust @ 25 kg/ha was evaluated during 1986-87 and 1987-88 against the pod-borers viz., lepidopteran Heliothis armigera Hubner and dipterous podfly Melanagromyza obtusa Malloch on pigeonpea T-15-15. All the insecticides were applied twice at fortnight interval initiating at 50% pod formation stage. All the insecticides evaluated exhibited significant potentiality in protecting the pods and grains against the pod-borer complex. Fenvalerate 0.02% and 0.01% [Fenval (R) 20 E. c. ]as well as fenvalerate 0.4% dust were found most effective in checking Heliothls infestation to the pods. The dust formulations of fenvalerate (O.4%) and quinalphos (1.5%) were equally effective in checking the Heliothis infestation. Maximum protection against the podfly infestation to the pods and grains was offered by fenvalerate 0.02%, but being at par with its lower concentration 0.01% and systemic organophosphate monocrotophos 0.04%. Fenvalerate 0.02% treated plot gave maximum increase in pigeonpea grain yield over control. It was followed by monocrotophos 0.04%, fenvalerate 0.4% dust, decamethrin 0.0015%, cypermethrln 0.006%, fenvalerate 0.01%, endosulfan 0.07%, quinalphos 0.05%, quinalphos 1.5% dust, fenvalerate [Sumicidin(R)] 0.01% and fenvalerate 0.005%. The mean C.B.R. for the two experiments ranged from 1 : 5.17 (quinalphos 0.05%) to 1 : 12.16 (fenvalerate 0.02%). None of the insecticides evaluated at the given doses caused any phytotoxic effect on the pigeonpea crop during both the years of experimentation. The fenvalerate residues in pigeonpea grains from its different treatments after 40 and 60 days of their applications were below the tolerance limit. However, the residues were more than 1 ppm in the podshells without grains of all fenvalerate treatments except fenvalerate 0.005%. The highest ovicidal action on the eggs of H. armigera (Hb.) was .exhibited by fenvalerate 0.02% and quinalphos 0.05%, whereas, fenvalerate 0.01%, monocrotophos 0.04%, decamethrin 0.0015%, cypermethrin 0.006%, fenvalerate [Sumicidin (R) ] 0.01%, fenvalerate 0.005% and endosulfan 0.07% were in descending order of their toxicity. Preliminary screening of pigeonpea germplasm consisting of 26 genotypes/entries for their susceptibility to the complex of pod-borers comprising two lepidopterans H. armigera (Hb.) and plume moth ,E. atomosa W. and podfly, M. obtusa Mall. was carried out under natural incidence of these pests. Among 13 early maturing entries/genotypes GAUT 82-105 was very less susceptible to both the lepidopterans, while GAUI 82- 92 and GAUT 83-23 had minimum podfly infested pods and grains. The higher yield response together with less susceptibility to the Heliothis and podfly was expressed by GAUT 82-104. ICPL-332 one of the 13 mid-late maturing entries screened was relatively very less susceptible to the infestation of the both lepidopteran borers and podfly whereas, GAUT 82-58 was even less susceptible to both the lepidopterans but highly susceptible to podfly. Heliothis susceptible entries were BDN-2 and G-15 but at the same time they had less infestation of podfly. The yield responses of GAUT 82-90 and GAUT 83-17 were higher in spite of sustaining relatively moderate infestation of Heliothis and podfly to the pods and grains. There was significantly more incidence of H. armigera (Hb.) in early maturing entries than that in mid-late maturing entries.
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AGRICULTURAL ENTOMOLOGY, AGRICULTURE, EVALUATION