screening elite genotypes and ipm of defoliators in groundnut

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5. DISCUSSION Of more than a hundred species of insect pests associated with groundnut crop, about ten are economically important in India. Defoliators mainly tobacco caterpillar, leaf miner, Helicoverpa armigera and bihar hairy caterpillar (BHC) are gaining importance in Karnataka. At present, pest management strategies rely on chemical control. Overuse of pesticides, especially in irrigated conditions has led to the outbreak of pests such as S. litura, destruction of natural enemies, development of resistance, environmental pollution and operational hazards followed by substantial erosion in net income. Further, farmers failed to get difference in sprayed and un-sprayed plots (Ranga Rao and Wightman, 1993).This indicates the failure of insecticides sprays, which add to the total cost of production and affect the environment adversely. As S. litura is one of the key pests of groundnut in the transitional tract of Karnataka in kharif and other irrigated places during rabi /summer, a study was envisaged to combat this noxious pest with an intention to evolve cost effective and environmentally safe approaches such as resistant cultivars, cultural practices and bio-pesticides. Worldwide there is an increased awareness that agricultural practices must be sustainable and environmentally friendly, greater emphasis is laid on integrated management of pests of which resistant cultivars form principle component. In groundnut, the Spanish bunch cultivars are most popular in India but they are highly susceptible to pests and diseases compared to spreading type. The research efforts have been successful in identifying resistant genotypes against S. litura (Wightman et al.; 1990, Patil et al.; 1991, Dwivedi et al.; 1993, Singh et al.; 1993, Nadaf et al.; 1995, Tiwari et al.; 1989, Prasad et al.; 1998, Rame Gowda and Basavana Goud, 2002). The present investigations were undertaken on IPM modules for groundnut pests and efforts were also made to know the nature of resistance of some selected elite genotypes of groundnut, which ultimately helps to develop strong IPM strategies. The results obtained in the light of available literature are discussed under here. 5.1 Field screening Different groundnut genotypes were screened against S. litura under artificial infestation in the field condition during 2009, rainy season. All the elite groundnut genotypes differed significantly in per cent defoliation and larval count per mt row. The damage ranged from 11.5 to 44.0 per cent in different genotypes. Maximum defoliation and number of larvae were observed in the JL-24 followed by GPBD-4. The genotypes viz., Mutant-III and ICGV- 86699 Tan recorded minimum damage and less number of larvae indicating their resistant nature (Fig. 1). The damage and number of larvae were moderate in GPBD-5, ICGV86699 Red and GPBD-6 (Table 1). Present findings corroborates with the findings of Prasad and Gowda, (2006) where the damage ranged from 34.33 to 83.67 per cent in different genotypes. Maximum defoliation was observed in the Dh-40, KRG-1, JL-24 and GPBD-4 and minimum damage was recorded in Mutant-45, ICGV-91180, NC Ac- 343 and Mutant-28-2. In screening study made by Patil et al. (1991), entries ICGV 87264 and 86598 have recorded the least damage (< 17.5%) and entries ICGV 86598 and 86125, ICGV 86350, 86276 and 87287 showed promise for resistance with less damage (< 27.5%) at two stages of screening (75 and 90 DAS). 5.1.1 Biological parameters of Spodoptera litura (F.) on selected elite groundnut genotypes Knowledge of an insect biology on the host plant is imperative in host plant resistance investigations. Investigating developmental and biological parameters of an insect has
Per cent defoliation 50 45 40 35 30 25 20 15 10 5 0 JL-24 (Susceptible check) Per cent defoliation No of larvae /mt row ICGV-86699 Red GPBD-5 ICGV-86699 TAN GPBD-6 MUTANT -III GPBD-4 Genotypes Fig. 1: Performance of elite groundnut genotypes for Spodoptera litura damage during Kharif 2009 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 No. of larvae/mt row
Page 1 and 2: SCREENING ELITE GENOTYPES AND IPM O
Page 3 and 4: CONTENTS Sl. No. Chapter Particular
Page 5 and 6: Figure No. LIST OF FIGURES Title 1.
Page 7 and 8: In some parts of the northern Karna
Page 9 and 10: mutants were systematically screene
Page 11 and 12: observed on Dwarf Mutant, the lowes
Page 13 and 14: Singh and Sachan (1991) recorded se
Page 15 and 16: Thontadarya and Nangia (1983) repor
Page 17 and 18: Monitoring with pheromone traps to
Page 19 and 20: 1. JL-24 (Susceptible check) 2. ICG
Page 21 and 22: Observations were recorded daily on
Page 23 and 24: Table 1: Performance of elite groun
Page 25 and 26: Third instar duration was significa
Page 27 and 28: Table 3: Gain in larval weight and
Page 29 and 30: Table 4: Biological parameters of S
Page 31 and 32: Table 5: In vitro biology of Spodop
Page 33 and 34: sunflower and N. rileyi, foxtail mi
Page 35 and 36: Table 7: Leaf hoppers population in
Page 37 and 38: Table 8: Thysanoplusia orichalcea p
Page 39 and 40: Table 10: Spilarctia obliqua popula
Page 41 and 42: 4.2.4.2 50 days after sowing The de
Page 43 and 44: Table 13: The management of Spodopt
Page 45 and 46: The early instar larvae scraped the
Page 47 and 48: Module I Table 16: Natural enemy po
Page 49 and 50: Table 18: Natural enemy population
Page 51: Table 19: Economics of IPM modules
Page 55 and 56: Larval period and Total development
Page 57 and 58: Larval Larval weight weight (g) (g)
Page 59 and 60: 5.2.3 Defoliator population in thre
Page 61 and 62: Pest population 1600 1400 1200 1000
Page 63 and 64: Gross returns and Net returns (Rs./
Page 65 and 66: REFERENCES Agasimani, C. A., Ravish
Page 67 and 68: Kennedy, F. J. S., Rajamanickam. K.
Page 69 and 70: Prasad, M. N. R. and Gowda, M. V. C
Page 71 and 72: Tiwari, S. N., Rathore, Y. S. and B
Page 73: SCREENING ELITE GENOTYPES AND IPM O

screening elite genotypes and ipm of defoliators in groundnut

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