screening elite genotypes and ipm of defoliators in groundnut

4. EXPERIMENTAL RESULTS
The results of the present study on biology of Spodoptera litura on seven elite
genotypes and integrated pest management modules for groundnut pests was undertaken at
Main Agricultural Research Station (MARS), University of Agricultural Sciences, Dharwad,
during Kharif, 2009 and results presented here under.
4.1 Field screening of groundnut genotypes
Seven 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 m row).
The damage ranged from 11.5 to 44.0 per cent in different genotypes. Maximum
defoliation and number of larvae / m row were observed in the JL-24 (44.0% and 4.0) followed
by GPBD-4 (33.5% and 3.5). The genotypes viz., Mutant-III (11.5% and 1.0) and ICGV-
86699 Tan (12.0% and 1.0) recorded minimum damage and less number of larvae / m row.
The damage and number of larvae were moderate in GPBD-5 (23.5% and 2.0), ICGV86699
RED (23.5% and 2.0) and GPBD-6 (28.5% and 2.0) (Table 1).
4.1.1 Biology of Spodoptera litura on elite genotypes under laboratory
conditions
Spodoptera litura was reared on seven groundnut genotypes viz., JL-24, ICGV-86699
Red, GPBD- 5, ICGV-86699 Tan, GPBD- 6, Mutant III and GPBD- 4. Various parameters of
growth and development of S. litura viz., number of days required for completion of each
larval instar, prepupa, pupa, pre oviposition, oviposition, post oviposition and also larval
weight, larval mortality at 5, 10 and 15 days after hatching, pupal weight, per cent survival on
each variety, per cent adult emergence, adult longevity and total life cycle were studied.
4.1.1.1 Larval period
During the entire larval period, the caterpillar moulted five times. Thus completed six
larval instars. A brief description of each larval instar is presented below (Table 2).
4.1.1.1.1 First Instar
Neonate larvae tiny, cylindrical and pale green with brown head. First abdominal
segment has a pair of black spots. Three dorsal stripes were seen all along the body. Larvae
congregated below the leaf at the site of egg laying. Scraped the epidermis which resulted in
the papery leaf devoid of chlorophyll.
The duration of first instar varied from 1.75 to 2.00 days in different genotypes. But
there was no significant difference between the genotypes tested.
4.1.1.1.2 Second instar
Except for increase in size, no marked change in body color was noticed. The larvae
remained in congregation but moved little away from the previous site and scraped the
chlorophyll resulting into thin papery leaf.
The duration of second instar was significantly longer (3.83 days) on the genotypes,
ICGV- 86699 Tan followed by Mutant III (3.50 days) than on other except GPBD-4 on which
the second instar duration was least 2.42 days.
4.1.1.1.3 Third instar
The larvae increased in size, turned pale green with brown head. A pair of black dots
on first abdominal segment and three dorsal stripes all along the body were prominent.
Larvae of this instar moved individually and punctured the leaflet.