Studies on host plant suitability of selected Rabi forage legumes for gram caterpillar, Helicoverpa armigera (Hubner)

Studies on the host plant suitability of different genotypes of Egyptian clover (Trifolium alexandrinum L.), Alfalfa (Medicago sativa L.) and Persian clover (Trifolium resupinatum L.) for growth and development of Helicoverpa armigera (Hubner) were conducted at the Entomology Laboratory, Forage and Millet Section, Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana during April-May, 2007. The highest larval weight of 511.95 ± 23.95 mg was attained on Berseem genotype BL 1 while the lowest larval weight (during the penultimate larval instar) of 288.36 ± 10.46 mg was on Shaftal genotype S 69. Total larval duration was maximum on S 69 (22.69 ± 0.58 days) and minimum (18.33 ± 2.08 days) on BL 1. The weight of pupa was lowest in S 69 (131.23 mg) and the highest in BL 1 (360.85mg). The longevity of female moths was higher than the male moths on all the genotypes. The mean number of eggs laid per female was minimum (565.70 ± 134.08) on S 69 and maximum (1087.80 ± 89.73 eggs) were recorded on BL 1. The total food consumption by H. armigera larvae from third instar larvae until pre-pupation was minimum (779.37 ± 2.93 mg) on S 69 and maximum (1408.44 ± 48.66 mg) on BL 1. Across the genotypes maximum (362.04 ± 31.48 mg) amount of food was consumed during the penultimate instar followed by the last instar (274.71 ± 19.56 mg). The overall mean AD was highest (39.69 ± 1.90) in Berseem genotype BL 10. The ECI values were highest (12.96 ± 1.92) in BL 42 and BL 22 recorded the lowest (7.78 ± 1.14) ECI value. Across the genotypes the ECI was highest (36.75 ± 0.35) in the third instar and declined in the fourth (17.53 ± 1.48) and fifth (7.69 ± 1.23) instars. The highest value (0.27 ± 0.02) of RGR was recorded on BL 42 followed closely by BL 1 (0.26 ± 0.009). On the other hand, very low (0.12 ± 0.004) growth rate was recorded on Shaftal genotype S 69. Based on total of 11 parameters, the overall order of genotypes in terms of host unsuitability for H. armigera, was S 69>BL 10>BL 22> LLC 5>BL 180> BL 42> BL 1. Thus, Berseem genotype BL 1 was the most suitable for development of gram caterpillar while Shaftal genotype S69 was the least suitable for this purpose.