BIOLOGY OF SPOTTED POD BORER, Maruca testulalis (Geyer), POPULATION DYNAMICS, VARIETAL SUSCEPTIBILITY AND CHEMICAL CONTROL OF INSECT PEST COMPLEX OF COWPEA [Vigna unguiculata (Linnaeus) Walpers]
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Date
2000
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AAU, Anand
Abstract
The investigations in cowpea on comparative biology and biometrics of spotted pod borer, Maruca testulalis (Geyer) on flowers and pods; preference for host, pupation and oviposition by M. testulalis; population dynamics of pest complex in relation to weather parameters susceptibility of varieties/genotypes to various insect pests and evaluation of various insecticides for their efficacy against insect pests and toxicity to ladybird beetles were carried out during 1997-99 at Gujarat Agricultural University, Anand Campus, Anand. The studies on comparative biology and biometrics indicated that the period of fifth instar (2.76 + 0.44 days) and total larval period (13.24 + 0.60 days) and total life cycle (30.44 /± 0.96 days) were significantly shorter in the culture reared on flowers as compared to the culture reared on pods. The growth index in the culture reared on flower (5.15) was also higher than in the culture reared on pod (4.57). The length and breadth of first instar larvae (2.99 + 0.16 mm and 0.72 ±0.01, respectively) and second instar larvae (4.72 + 0.06 mm and 0.87 + 0.01 mm), respectively; length of third instar larvae (9.26 + 0.13 mm); width of head capsule in second (0.38 + 0.01 mm), third (0.47 + 0.02 mm) and fifth (0.63 + 0.02 mm) instar larvae; breadth of male pupa (2.45 + 0.08 mm); length of female pupa (13.30 + 0.32 mm) and width of .female aduh (24.53 + 0.43 mm) were significantly more in the culture reared on flowers compared to the culture reared on pods. Two cultures did not differ significantly in respect of biometrics and period of rest.of the stages. The hatching percentage (85.24 + 1.88) was also significantly higher in the culture reared on flowers than that on pods (82.64 + 2.38), but two culture did not differ in fecundity. Cowpea was found most preferred host for feeding on flowers and pods compared to green gram, black gram, pigeonpea and Indian bean. Cowpea leaves were significantly more preferred for pupation than pods, flowers and soil. Cowpea was also most preferred host for oviposition compared to green gram and black gram. Flower was most preferred part for oviposition compared to pod and leaf in all the three hosts. The maximum and minimum population of aphid (Aphis craccivora Koch.), leafhopper (Amrasca kerri Pruthi), whitefly [Bemisia tabaci (Gennadius)], thrips (Megaleurothrips sjostedti Trybom), leafminer [Acrocercops caerulea (Meyrick)] and ladybird beetles [Menochilus sexmaculatus (Fabricius) and Coccinella septempunctata Linnaeus] was found in December and January, February and November, September and February, August and December, July and October and December and May sown crops, respectively. The maximum and niininuim per cent pod damage by pod borer, M. icslulalis was in August and October sown crops, respectively. The populations of aphid and ladybird beetles were found higher during winter season and lov/er during summer season. The population of thrips and leafminer as well as per cent pod damage by pod borer was found to be higher in kharif while it was lower during summer. Leafhopper and whitefly populations remained considerably higher during summer while it was lower during winter. The overall relationship between pest population (Y) and meteorological parameters (X) in the form of regression equation with coefficients of determination (R2 ) given in bracket was : Y = 91.3441 - 1.5608 X4 - 0.5103 X2 - 3.0824 X14 (R2 = 0.3802) for aphid, Y = -2.1656 + 0.1323 X2 - 0.1626 X14 (R2 = 0.2455) for leafhopper, Y = 0.7040 - 0.0230 X12 - 0.0252 X13 -0.0596 X14 (R2 = 0.3793) for whitefly, Y = 2.4997 + 0.3654 X12 - 1.2646 X14 (R2 = 0.2685) for thrips, Y = 0.0560 + 0.0169 X6 + 0.0038 X15 (R2 = 0.2978) for leafminer, and Y = 0.6416 - 0.0101 X12 + 0.0048 X16 (R2 = 0.6087) for ladybird beetles. For per cent pod damage by pod borer (Y), the regression equation with meteorological parameters (X) was: Y= 2.2804+2.1986X5 -2.2796X,2 (R2 =0.5223). In above equations, X2, X4, X5, Xe, X12, Xo, X14, X15 and X16 stand for maximum temperature, mean temperature, morning relative humidity, evening relative humidity, evening vapour pressure deficit, mean vapour pressure deficit, wind speed, rainfall and aphid population, respectively. The chronological order of different cowpea varieties based on overall rank for their susceptibility against pest complex was : EC-244438 < EC- 244241 = VKP-4506 < IC-20683 < EC-241043 < IFC-8401 < EC-240887 < CS- 88 < B-2 = CS-39 = EC-241021 < B-1 = 82-1-B < GC-3 < M-lOO = A-1 = A-2 < GC-2 = GC-K Pusa Phalguni. Based on overall rank for the bio-efficacy against pest complex plus safety to ladybird beetles, the chronological order of various insecticides with green pod yield in kg/ha and incremental cost benefit ratio (expect for pymetrozine and difenthiuron), respectively given in bracket was : monocrotophos @ 0.04% (9210 and 1:103.14) > phosphamidon @ 0.03% (9062 and 1:150.62) = dimethoate @ 0.03% (8988 and 1:118.01) > methyl-o-demeton @ 0.03% (9240 and 1:111.29) > endosulfan @ 0.07% (7383 and 1:58.14) > chlorpyriphos @ 0.04% (7422 and 1:58.53) > quinalphos @ 0.05% (7141 and 1:47.30) > deltamethrin @ 0.0014% (6664 and 1:65.94) > cypermethrin @ 0.05% (6114 and 1:52.78) = pymetrozine @ 0.025% (6129 ) > Decidan, a mixture of deltamethrin + endosulfan @ 0.05% (5867 and 1:26.55) > difenthiuron 0.05% (6035 ) > Gronim, a neem based formulation @ 0.3% (4612 and 1:20.58) > neem oil@ 1% (4949 and 1:35.04).
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AGRICULTURAL ENTOMOLOGY, AGRICULTURE, A STUDY