DEVELOPMENT OF LIFE TABLES FOR STEM BORER, Chilo partellus (SWINHOE) ON PROMISING GENOTYPES OF MAIZE AND ITS MANAGEMENT WITH BIORATIONAL INSECTICIDES
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Date
2017
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Acharya N.G. Ranga Agricultural University
Abstract
Investigations on life tables, seasonal incidence, crop loss estimation and
management of maize stem borer, Chilo partellus (Swinhoe) with biorational
insecticides were carried out at Agricultural Research Station, Darsi, Prakasam district
during kharif and rabi 2014-15 and 2015-16.
Total life cycle of C. partellus (egg to adult emergence) was completed in 54.5,
54.0, 51.5, 51.4, 55.0 and 48.6 days in kharif and 58.7, 59.5, 56.8, 57.5, 58.8 and 53.3
days in rabi on DHM 117, DHM 121, Madhuri, Priya, Amber and 30V92, respectively.
Forty eight life-tables were constructed for C. partellus on six maize cultivars
viz., DHM 117, DHM 121, Madhuri sweet corn, Priya sweet corn, Amber pop corn and
30V92. In each season of kharif and rabi 2014-15 and 2015-16 two generations of the
pest were studied. The survivorship curves drawn for all the generations in each year
indicated that the mortality rate was higher at the small larval stage. Generation
survival declined from first generation in first crop during kharif 2014 to second
generation in fourth crop during rabi 2015-16 in all maize cultivars. The trend index
was positive (more than one) and varied in all generations. Key factor analysis revealed
major mortality factors influencing population fluctuation included larval parasitoid
particularly Cotesia flavipes and unknown causes during small and medium larval
stage. Density dependant related mortality was observed in the life cycle of
C. partellus. The lowest mean total K value (0.45) was observed on 30V92 maize
cultivar. Correspondingly, the highest mean values of generation survival (0.38) and the
trend index (40.2) were obtained on 30V92 cultivar indicate more susceptibility to
C. partellus. The high mean total K (0.59) and lowest generation survival (0.27) and the
trend index values (25.2) were observed on Amber pop corn.
C. partellus larval population, per cent infestation and per cent larval parasitism
differed between years and seasons on maize. Natural enemies were recorded in more
numbers when pest population was high. Larval population and plant infestation by
C. partellus exhibited significant negative correlation with minimum temperature on
average basis of two years during kharif. Maximum temperature had significant
positive correlation with plant infestation on average basis of both study years in rabi
season. Morning and evening relative humidity showed significant positive correlation
with plant infestation on cumulative basis of both kharif 2014 and 2015, while evening
relative humidity showed significant negative correlation during rabi 2014-15 and
2015-16 pooled analysis. Cumulative basis of two study years in kharif, parasitism by
C. flavipes showed a significant positive correlation with larval population and plant
infestation, whereas pooled average of rabi 2014-15 and 2015-16, larval parasitoid had
significant positive correlation with larval population only and non-significant positive
correlation with plant infestation.
Natural infestation of C. partellus resulted in the yield loss of 56.69 and 3.19 in
grain yield and 100-grain weight, respectively across the different dates of sowing. The
unprotected plot recorded significantly higher dead heart incidence (9.30 and 2.38%),
larval population (1.89 and 0.65 per plant), foliage damage (43.08 and 22.24%), stem
tunneling (11.72 and 3.30%) and exit holes (2.55 and 0.84) as compared to protected
ones. The per cent grain yield loss increased with increase in larval density. The
maximum loss in grain yield (45.68%) and 100-grain weight (19.25%) occurred in the
treatment with 8 larvae per plant. The economic injury level was worked out at 2.74
larvae per plant.
Among the botanical pesticides, entomogenous microbes, insect growth
regulators and natural insecticides in the management of C. partellus in maize, foliar
application of chlorantraniliprole 18.5% SC, spinosad 45% SC and whorl application of
chlorantraniliprole 0.4% GR significantly reduced the damage of C. partellus and larval
population over untreated control. The marginal increase in maize grain yield was in
the order of 108.1, 99.8 and 88.4 per cent, respectively for the treatments
chlorantraniliprole 18.5% SC, spinosad 45% SC and chlorantraniliprole 0.4% GR over
untreated check. The population of natural enemies viz., C. transversalis,
C. sexmaculata and predatory spiders remain unaffected by these biorationals. The
incremental cost benefit ratio was 12.28 in chlorantraniliprole 18.5% SC which was
next best to monocrotophos 36% SL (19.52).
Description
D5416
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