BIOECOLOGY OF SPOTTED POD BORER, Maruca vitrata (Fabricius), BIOEFFICACY AND RESIDUAL STATUS OF SOME INSECTICIDES IN RELATION TO INSECT PEST COMPLEX OF COWPEA [Vigna unguiculata (Linnaeus) Walpers]
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Date
2004
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AAU, Anand
Abstract
The investigations in cowpea on comparative biology and biometrics of spotted pod borer, Maruca vitrata (Fabricius) on different host crops (cowpea, green gram, black gram, pigeonpea and Indian bean), population dynamics in relation to weather parameters and field life table of M vitrata, evaluation of various insecticides for their efficacy against insect pest complex and toxicity to lady bird beetles and residual status of some insecticides on cowpea were carried out during 2001-2003 at Anand Agricultural University, Anand. The studies on comparative biology and biometrics indicated that significantly higher length (mm) of egg (0.64), 1st (3.18), 3rd (9.39), 4th (12.05) and 5th (16.23) instar larva, male (13.55) and female (13.64) pupa, male (11.81) and female (11.99) moth; significantly higher breadth (mm) of 1st (0.73), 2nd (0.88). 3rd (1.66), 4th (2.81) and 5th (3.56) instar larva and female moth (24.85); significantly higher width (mm) of head capsule in 1st (0.29), 2nd (0.39). 3rd (0.52), 4th (0.59) and 5th (0.66) instar larva; significantly shorter period (days) of egg (2.32), 1st (2.30), 3rd (2.75), 4th (2.75), 5th (2.60) instar larva; significantly shorter total larval (13.71 days), pre-pupal (1.59 days), pupa! (5.36 days) and pre-oviposition (1.10 days) periods; significantly longer oviposition periods (4.30 days) in the female and adult period (6.40 days) of male; significantly shorter total life cycle (29.36 days) of female and significantly higher fecundity (41.80 eggs) and growth index (5.71) were recorded in the culture of M. vitrata reared on cowpea [V. unguiculata (L.)] as compared to green gram [V. radiata (L.)], black gram [V. mungo (L.)], pigeonpea [Cajanus cajan (L.)] and Indian bean [Lahlah purpureus (L.)]. Based on these parameters, it was concluded that cowpea is the most preferred host for growth and development of M. vitrata. Per cent damaged pods ranged from 2.20 to 55.52 and 2.77 to 29.43 in kharif cowpea crop during 2001 and 2002, respectively. The infestation commenced 1 to 2 week(s) after initiation of pod setting and it was higher in the month of August. The correlation coefficient was significant only in case of maximum and mean temperatures having positive correlation and mean relative humidity having negative correlation with per cent pod borer damage during kharif, 2001. It was significant with evening vapour pressure (X8) having positive correlation in kharif, 2002. The regression equations showing relationship between per cent pod borer damage (Y) and mean temperature (X5) was found to be : Y = -656.08 + 23.7570 X5 [R2 = 0.4161] for kharif 2001 and Y =-136.18 + 6.6927 X8 [R2 = 0.4314] for kharif, 2002. Field life table studies on M vitrata revealed that a larval-pupal parasite Agathis sp. accounted for 48.14 and 32.52 per cent mortality in 2001 and 2002, respectively. Studies on key mortality factor analysis indicated that big size larvae and pupal stage were most valuable stages for managing this pest. Based on overall rank for bioefficacy against pest complex plus safety to lady bird beetles, the chronological order of various insecticides with green pod yield in kg/ha and incremental cost benefit ratio, respectively given in bracket was : lambdacyhalothrin @ 0.0025% (3337 and 1:31.68) > methyl-o-demcton @ 0.025% (3160 and 1:29.99) > fenvalerate @ 0.01% (2882 and 1:33.50) > deltamethrin @ 25% tablet (6962 and 1:49.53) > alphamethrin @ 0.01% (3742 and 1:28.53) > deltamethrin @ 0.0014% (5729 and 1:71.53):- endosulfan fa) 0.07% (5150 and 1:45.50) > quinalphos @ 0.05% (4045 and 1:29.21) > indoxacarb @ 0.00725% (4454 and 1:18.45) > methomyl @ 0.08% (5364 and 1:16.53) > azadirachtin @ 0.001% (2498 and 1:13.08) > Btk@ 0.75 kg/ha (2188 and 1:2.51) > NSKE @ 5% (1890 and 1:12.98).
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AGRICULTURAL ENTOMOLOGY, A STUDY