screening elite genotypes and ipm of defoliators in groundnut

observations were also made by Leuk and Skimmer (1971) and Garner and Lynch (1981),
where pupal weight, mean percentage of pupae and moth emergence were significantly less
and the pupal duration was long from larvae fed on foliages of the resistant than susceptible
groundnut cultivars. Prasad and Gowda (2006) reported that the larvae fed on the resistant
genotypes, NC Ac 343, Mutant 28-2, ICGV-86031 and R 9227 showed less per cent pupal
survival and moth emergence compare to susceptible checks. The effect of resistance on
pupal development confirms the antibiosis mechanism of resistance existing in the resistant
genotypes (Painter, 1951).
5.1.1.4 Pre-oviposition, oviposition and post oviposition period
The duration of pre-oviposition, oviposition and post-oviposition were also affected in
larvae fed on foliage of resistant genotypes. The genotypes Mutant III and ICGV-86699 Tan
recorded longer pre-oviposition and shorter oviposition, post-oviposition period compare to
susceptible genotypes GPBD-4 and JL-24 (Table 5).
5.1.1.5 Adult longevity
Adult longevity was significantly longest on susceptible genotypes JL-24 and GPBD-4
and shorter on resistant genotypes Mutant III and ICGV-86699 Tan (Table 4). The similar
observations also made by Sreenivasa et al. (1997), where the development of S. litura was
shortest (32.25 days)on Dh-3-30 with adult surviving maximum of 10.5 days and longest
developmental period on ICGV-86031 (37.3 days) with adult surviving for maximum of 9.5
days. The effect of these genotypes on adult longevity of S. litura could obviously due to
chemical factor (i.e. antibiosis).
5.1.1.6 Fecundity
The resistant effect of Mutant III and ICGV- 86699 Tan were also affected the
fecundity as disclosed by total number of eggs laid by the female moths developed from
larvae fed on these genotypes (Table 4 and Fig. 3). This could be an important criterion for
selecting resistant genotypes. Therefore, the antibiosis effect from these genotypes could
result theoretically in cumulative seasonal reduction of eggs. Painter (1951) stated that
resistance at this level could be of high value as control measure.
Higher mortality of neonate larvae on Mutant III and ICGV- 86699 Tan compared to
JL-24 and GPBD-4 were perhaps because of the most common and easily observable
characteristics of antibiosis. Low larval and pupal weight, extension of larval, pupal, preoviposition,
oviposition and post-oviposition period, lower fecundity, per cent pupal survival
and adult emergence confirm the possible role of antibiosis as mechanism of resistance in
these promising genotypes with varying degrees, as elucidated by Painter (1951).
Insect resistance in these genotypes may be due to high laminar thickness, low water
content, fecundity and growth index (Tiwari et al., 1989; Dwivedi et al., 1993; Patil et al.,
1995) and also due to the presence of anti- insect properties like isomers of caffeol quinic
acid (Stevenson, 1993).
If these two resistant elite genotypes are agronomically superior in all characters
including yielding ability. These can be recommended for cultivation in farmer’s field after
evaluating on large scale farmers field or otherwise these can be utilized as resistant source
in improving agronomically superior susceptible varieties of groundnut.
5.2 Evaluation of IPM modules in groundnut
In recent years groundnut has suffered heavy losses due to severe outbreak of the
tobacco caterpillar, Spodoptera litura (F.). The farmers fail to adopt management practices
because of high populations during monsoon rains and overlapping generations. Besides,
many other sucking pests of this crop, including leafhoppers, Empoasca kerri Pruthi and
thrips, Thrips palmi Karny, damage the foliage extensively. In view of environmental impact of
pesticides and development of resistance to pesticides by S. litura (Rame Gowda, 1999) the