screening elite genotypes and ipm of defoliators in groundnut

stage, with the female consuming more food than the male. Larval mortality and the sex ratio
seem to have no relation with the amount of food consumed per species.
According to Ghumare and Mukheijee (2003) the five host plants [castor (Ricinus
communis L.), cotton (Gossypium hirsutm L.), tomato (Lycopersicum esculentum M.) mint
(Mentha arvensis L.) and cabbage (Brassica oleracea L.)] belonging to different families were
used to study the performance of the Asian armyworm, S. litura. Highest consumption of food
and dry weight gain was observed in larvae fed on castor. Mint did not support optimum larval
growth because of low digestibility and low efficiency of conversion of digested food to body
matter. Dry weight gain ranged from 26.64 mg on mint to 86.80 mg in castor.
The biological parameters of S. litura were studied on cotton and different weed
plants viz., itsit (Trianthema portulacastrum), tandla (Digera arvensis) and thakra (Tribulus
terrestris) under laboratory conditions at Entomology Research Farm and Laboratories of the
Department of Entomology at Punjab Agricultural University, Ludhiana during 2006 Kharif
season. The study suggests that S. litura showed faster larval development on all three
weeds as compared to cotton, although the larval and pupal survival was lower on these
weeds. These results suggest that the role of weeds in the development of S. litura cannot be
overlooked (Inderjit et al., 2006).
Dara and Prasad (2007) estimated the population parameters of S. litura on green
gram (Vigna radiate L.), black gram (Vigna mungo L.), groundnut (A. hypogaea) and chilli
(Capsicum annuum L.) along with castor bean as control in the laboratory. Field-collected egg
masses of S. litura were used to start the initial colonies. S. litura population showed a
positive trend on all host plants. The population parameters net reproductive rate, intrinsic
and finite rates of increase, weekly multiplication rate, and potential fecundity were highest on
castor bean, followed by greengram, blackgram, groundnut and chilli. Accordingly, the mean
generation time and doubling time were shortest on castor bean, followed by greengram,
blackgram, groundnut and chilli. Stable age-distribution showed that egg, larvae and pupae
contributed to > 99 per cent of the population stable age.
Maghodia and Koshiya (2008) studied that the life history of S. litura at 27.1 0 C in the
laboratory on five different crops presumably observed as host plants of S. litura. The data
were analyzed based on age-stages and variability of developmental rate among individuals
of the pest. The highest intrinsic rate of increase (r), the finite rate of increase and the net
reproduction rate (Ro) of S. litura were 0.174, 1.192 females/day, 1370.74 offspring/individual,
respectively, observed on castor, while the highest mean generation time (T) 45.48 days was
observed on cotton. The life expectancy of newly deposited eggs was 17.34, 17.44, 16.39,
17.45 and 17.98 on castor, tobacco, groundnut, cotton and cabbage, respectively. The age
specific fecundity of S. litura was 395.64, 179.32, 186.25, 292.64 and 25.14 progenies per
day on the 42 nd , 44 th , 41 st , 46 th and 51 st days for castor, tobacco, groundnut, cotton and
cabbage, respectively. Studies on age-specific distribution of the pest on different hosts
revealed that the eggs and larvae contributed the highest to the population, whereas the
contribution of the pupae and adults was negligible.
2.1.1.2 Biology of Spodoptera litura on different varieties of groundnut
Host plant resistance can be exploited as an effective and environment friendly
component of pest management. At present, S. litura is a prominent defoliator associated with
groundnut crop. So incorporation of resistance to this in suitable varieties has been high
priority for groundnut breeders in association with entomologists.
Tiwari et al. (1980) studied on the survival and weight gain in larvae of S. litura reared
on 9 varieties of groundnut. Four days after feeding, larval survival was similar on all varieties
except C-501, where high mortality rate was recorded. This trend was also observed 8 days
after feeding, but after 12 days the mortality rate did not change. Larvae feeding on C-501
weighed 1.26 mg after 4 days, while on Dwarf Mutant larval weight was 4.41 mg. Larval
weight after 8 days' feeding was significantly greater on Dwarf Mutant than on the other
varieties, and was lowest on C-501. After 12 days of feeding, the greatest weight gain was