Bio-ecological Management of Major Insect Pests of Soybean
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Date
2017
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MPUAT, Udaipur
Abstract
Investigations on “Bio-ecological management of major insect pests of
soybean ” were carried out in the Department of Entomology, Rajasthan College of
Agriculture, MPUAT, Udaipur, during the kharif seasons from 2015 to 2016 with a
view to study the influence of plant nutrition on the incidence of major insect pests of
soybean; impact of farmscaping on the natural enemy diversity; efficacy of biopesticides
for insect pest management; and prepare a pictorial field diagnostic key to
identify dominant insect pests of soybean.
During the two successive crop seasons (kharif, 2015 & 2016), the major
insect pests of soybean were the stem fly, whitefly, jassids, foliage-feeding weevils,
leaf folder, semiloopers and the tobacco caterpillar. The associated natural enemies
included the predatory pentatomid bug (E. furcellata), spiders and stem fly parasitoids
during the two-year study, both when soybean was cultivated farmscaping with
marigold and without farmscaping. The mean atmospheric temperature had significant
positive correlation with major insect pests of soybean in kharif 2015, but in kharif
2016 the mean atmospheric temperature showed a significant positive correlation only
with the population of weevils (r= 0.61) and other lepidopterans (r=0.61); whereas, a
significant negative correlation was exhibited for jassids and semiloopers. The total
rainfall evinced a significant negative correlation with the whitefly and jassid
population of soybean during 2015; whereas in the crop season 2016, the mean
relative humidity showed a significant negative correlation with weevils and other
lepidopterans. The population of weevils and other lepidopterans showed a significant
negative correlation with total rainfall. The mean relative humidity and rainfall
exhibited a significant positive correlation with semilooper population (respective
correlation coefficient values being 0.88 and 0.59) during kharif, 2016. Among the
insect pests of soybean, jassids had the maximum seasonal mean population, mean
density and relative density during both years as compared to other insect pests both
under marigold farmscaping and without marigold farmscaping in soybean. The
Shannon-Weiner Diversity Index values did not vary significantly when soybean was
cultivated under farmscaping with marigold and without farmscaping. As for the
natural enemies, the predatory pentatomid bug E. furcellata had the maximum
seasonal mean population, mean density and relative density. The Shanon-Weiner Diversity Index values were relatively more for soybean cultivated with marigold
farmscaping. The mean atmospheric temperature evinced significant positive
correlation with the population of spiders (r= 0.61) and the pentatomid bug (r= 0.67).
The mean population of the pentatomid bug showed significant positive correlation
with tobacco caterpillar population only when soybean was cultivated with marigold
farmscaping in both the years. Parasitization of stem fly maggots was more during
kharif 2016.
When enhanced potassium nutrition (K2O @ 20 kg ha-1) was given to the
soybean crop, significantly lower mean population of the major insect pests was
recorded; in response, significantly lower population of spiders and predatory
pentatomid bugs were recorded. Soybean without enhanced application of potassium
harboured significantly more pests. The effect of enhanced potassium application
through muriate of potash [K2O @ 20 kg ha-1] under farmscaping with marigold
evinced significantly lowest mean population of stem fly. Significant variation in stem
tunnelling by the stem fly was observed in both the years.
Farmscaping soybean with marigold had significantly lower mean population
of whiteflies, weevils, leaf folder, semiloopers and tobacco caterpillar; while, the
population of jassids did not differ significantly between soybean without
farmscaping and soybean farmscaped with marigold during both the years of study.
Likewise, farmscaping with marigold in soybean resulted in significantly higher
population of the common natural enemies: spiders and predatory pentatomid bugs.
All the enhanced potassium treatments in soybean during both the crop
seasons had significantly higher yields than that without potassium enrichment.
Farmscaping soybean with marigold had a significant influence on yield with a wider
per cent increase in yield ranging from 37.65 to 96.08 per cent during kharif 2015 as
compared to 17.24 to 35.71 per cent during kharif 2016.
The overall efficacy of the bio-pesticides evaluated after three sprays indicated
that A. indica seed kernel extract (5%) was significantly most effective in causing the
maximum population reduction of whiteflies and jassids 1 and 3 days after the first,
second and third sprays; however, it did not show any significant effect on whiteflies
and jassids 7 days after spray. The anti-feeding activity of bio-pesticides on
Spodoptera litura infesting soybean showed that the larval mortality was noticed 3
days after treatment, and the maximum larval mortality of S. litura was recorded in
SL-NPV-250 LE/ha, followed by A. indica seed kernel extract (5%) and A. indica oil
(1%).
Morphological characterization of the major insect pests comprising 6 species
of order Lepidoptera, 3 species of Hemiptera, 2 species of Coleoptera and 1 species of
Diptera has been illustrated and described along with pictorial keys.
Description
Bio-ecological Management of Major Insect Pests of Soybean
Keywords
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Citation
Meena and Swaminathan, 2017