EFFECT OF LIGHT ON BIOLOGY, VARIETAL SCREENING AND MANAGEMENT OF LESSER GRAIN BORER (Rhyzopertha dominica Fab.) IN STORED MAIZE 3731
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Date
2023-07
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JAU JUNAGADH
Abstract
Light and dark effect on biology, varietal susceptibility, botanicals powders/oil, Rhyzopertha dominica (Fabricius), maize
Investigations were carried out at the Post Graduate Storage Laboratory,
Department of Entomology, College of Agriculture, Junagadh Agricultural
University, Junagadh during the year 2022-2023 on “Effect of light on biology,
varietal screening and management of lesser grain borer (Rhyzopertha dominica Fab.)
in stored maize”.
The study on the effect of light on the biology of R. dominica was made on
maize variety GAWMH-2 under laboratory conditions at an average temperature of
30 ± 1˚C and 70 ± 5 per cent RH. The freshly laid eggs were white, translucent,
typically round at one end and pointed at another end and turn into light red colour
which was an indication of the advancing incubation period. The highest incubation
period was recorded at 24 hr light 7.96 ± 0.97 days, while the lowest was observed at
24 hr dark 6.48 ± 0.77 days and in 16 hr Light: 8 hr Dark incubation period was 6.64
± 0.81 days. The newly hatched larva was white with a brownish head. The larva
entered the grain and complete the larval and pupal stages within the grain. Thus, the
total larval and pupal period was recorded. The shortest larval duration was observed
at 24 hr dark 31.5± 2.04 days, whereas the longest one was shown at 24 hr light 42.48
± 2.29 days and in 16 hr Light: 8 hr dark 32 ± 2.78 days. These results show that
continuous light increases the larval developmenal period. Total developmental period
44.88 ± 2.81 days in 24 hr dark, 51.96 ± 2.44 days in 24 hr light and at 16 hr Light: 8
hr 45.92 ± 3.16 days.
In 24 hr light Pre- oviposition, oviposition and post- oviposition average
duration were 7.08 ± 0.95, 33.4 ± 2.78 and 6.28 ± 0.93 days, respectively. Pre oviposition, oviposition and post- oviposition average duration in 24 hr darkness were
6.90 ± 1.20, 36.4 ± 3.35 and 6.64 ± 0.75 days and in 16 hr Light: 8 hr Dark were 6.24
± 1.05, 34.52 ± 3.08 and 6.52 ± 0.65 days, respectively. Adults in 24 hr darkness lived
longer, with the males' average longevity 35.64 ± 1.86 days, whereas in females 42.08
± 2.08 days than those reared under continuous 24 hr light, the males longevity was
33.68 ± 1.79 days, whereas in case of females average longevity was 39.56 ± 2.53
days. The decrease of light from 24 hr to 16 hr light and 8 hr Dark average longevity
of males was 35.08 ± 1.63 days and in females it was 40.24 ± 2.31 days.
Fifteen maize varieties/genotypes were screened to know their resistance/
susceptibility against R. dominica. Significantly minimum adults developed (40.59),
per cent loss (7.65) and per cent germination loss (12.94) after 6 months of storage
period was observed in the variety GYH-1907 followed by GWH-1706. The
chronological order of superiority of the varieties based on overall performance was
GYH-1907 > GWH-1706 > GYH-2111 > GWH-1704 > GYH-2107 > GYH-2107 >
GWH-2006 > GWH-1902 > GYH-2003> GYH-2109>GWHQP-1806>GWHQPM 1802 > GWH-2106 > GWH-2102 > GYH-0965 > GYH-1901.
In the evalution of different nine botanical oils @ 10 ml per kg and powders
10 g per kg of maize grains were tested for their efficacy in protecting stored maize
against R. dominica. Maximum adult mortality and minimum grain damage were
recorded in grain tested with neem seed kernel powder and neem oil. Castor oil,
karanj oil, mustard oil, black pepper powder and garlic powder were found medium in
their effectiveness. Clove and mint powder were the least effective against R.
dominica in maize. The per cent adult mortality decreased as the storage period
increased. The highest germination (86.01 %) was observed in seed treated with neem
seed kernel powder and it was at par with neem oil (83.72 %) treated seed as
compared to control (63.34 % germination).