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20232
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Subject: Entomology × End date: 2023 × Start date: 2023 × Thesis Type: Ph.D ×
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    Biology, population dynamics, crop losses and management of emerging pest, Spodoptera exigua (Hübner) in chickpea
    (Punjab Agricultural University, 2023) Sidhu, Kawartej Singh; Ravinder Singh
    Field and laboratory studies were conducted to determine the biology, population dynamics, crop losses and management of Spodoptera exigua in chickpea during Rabi 2021-22 and 2022-23 at PAU, Ludhiana. Eggs of S. exigua were laid in masses covered with scales. The larval and pupal period lasted for 16.79 and 9.37 days on chickpea, whereas on mungbean it was 14.69 and 8.46 days, respectively. The best developmental and reproduction values were recorded on mungbean as compared to chickpea. In population dynamics, early, normal, and late sown chickpea, mean number of larvae ranged from 0.00 to 15.10, 0.00 to 13.20, and 0.40 to 11.60, respectively. As the sowing dates delayed, number of egg masses, larval number and foliar damage by S. exigua decreased. In estimation of crop losses, there was no foliar damage where the crop was protected by nylon mesh cages. Protected treatment had significantly lowest mean foliar and pod damage than unprotected treatment. In insect density method, lowest mean seed yield was recorded in treatment with highest larval infestation of seven larvae per meter row (1079 kg ha-1) as compared to control (1623 kg ha-1). In cultural and mechanical control of S. exigua, highest mean yield (1628kg ha-1) was recorded in treatment consisting of hand collection and destruction of egg masses and young larvae of S. exigua followed by where 2 rows of linseed were sown as intercrop after 10 rows of chickpea (1527 kg ha-1). Among different biopesticides/biorationals tested against S. exigua in chickpea, chlorantraniliprole 18.5 SC @ 125 ml ha-1 was found most effective over all other treatments. S. exigua is emerging as a serious pest of chickpea under Punjab conditions which can be managed by using cultural, mechanical and chemical methods.
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    Influence of abiotic factors on development and behaviour of rice leaf folder, Cnaphalocrocis medinalis (Guenee)
    (Punjab Agricultural University, 2023) Simranpreet Kaur; Suri, K S
    The present studies on “Influence of abiotic factors on development and behaviour of rice leaf folder, Cnaphalocrocis medinalis (Guenee)” were conducted at Punjab Agricultural University, Ludhiana during 2019-22. The impact of variable minimum:maximum temperature for 10:14 h, CO2 and RH on C. medinalis revealed that larval duration, pupal duration, adult emergence, male longevity, female longevity, incubation period and hatchability decreased, whereas female proportion and fecundity of C. medinalis increased with increase in temperature (22:32°C to 26:35°C), CO2 (400 to 450 ppm) and RH (75 to 85%). The shortest larval duration of 7.5 days, pupal duration of 6.0 days, male longevity of 4.5 days, female longevity of 7.75 days, incubation period of 2.25 days, hatchability of 47.19 per cent and least adults emergence (5.25 adults) was recorded at elevated temperature (26:35°C), CO2 (450 ppm) and RH (85%), whereas the maximum fecundity (142.25 eggs) and female proportion (0.99) was recorded at the same elevated conditions. Food consumption, CI, AD and RGR increased, whereas ECI, ECD and RCR of C. medinalis larvae decreased with increase in temperature, CO2 and RH. Maximum food consumption (0.0450 g larva-1), CI (0.0965), AD (84.43%) and RGR (0.0770 mg mg-1day-1) was recorded at elevated temperature (26:35°C), CO2 (450 ppm) and RH (85%). Leaf folding pattern, employing double and multiple leaves for feeding and pupation was witnessed at elevated temperature, CO2 and RH. Activity of enzymes viz. AChE, Esterase, GST, Proteases and SOD in C. medinalis larvae increased as 4.96 μg of free thiol formed/min/mg protein, 9.86 μg of β-napthol formed/min/mg protein, 1.81 mmole of CDNB-GSH conjugate formation/min/mg protein, 3.49 mmol of tyrosine released/min/mg protein and 3.80 units/min/mg protein, respectively, whereas activity of Catalase decreased (7.48 µmoles of H2O2 decomposed/min/mg protein) with increase in temperature from 22:32°C to 26:35°C, CO2 from 400 to 450 ppm and RH from 75 to 85 per cent. Total sugars, reducing sugars, phenols and flavonols in rice plants showed a positive linear regression equation while proteins and amino acids followed a negative linear regression equation, whereas chlorophyll showed a non-linear regression equation with temperature, CO2 and RH. The results of present study would facilitate the adoption of appropriate adaptation measures for C. medinalis management with respect to climate change.