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Subject: Entomology × End date: 2023 × Start date: 2023 ×
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    Diversity, seasonal incidence and damage assessment of Oxycarenus spp. on cotton
    (Punjab Agricultural University, 2023) Noor Mahammed N R; Pandher, Suneet
    The study on „Diversity, seasonal incidence and damage assessment of Oxycarenus spp. on cotton‟ was conducted at PAU, RRS Faridkot during Kharif 2022-23. Increasing incidence and damage incurred due to dusky cotton bug on cotton during the last few years necessitated to conduct the present study in north India. The results of first experiment were based on collection of dusky cotton bug samples from 31 locations spread across three states of Punjab, Haryana and Rajasthan and revealed that mt-COI gene based molecular identification doesn‟t confirm Oxycarenus at species level. The second experiment on seasonal incidence of dusky cotton bug was recorded on Bt cotton hybrid G. hirsutum RCH 650, non Bt G. hirsutum var. RS 2013 and G. arboreum var. LD 1019 at weekly intervals from 20 randomly selected plants (five squares/flowers/bolls) from each cultivar starting from the appearance of bugs (June) till the harvest of the crop (December). The results revealed that population of Oxycarenus spp. started during square formation stage (July last week), reached peak (around 100 bugs per 5 bolls) during complete boll opening stage (November second week) and remained present till the harvest of crop. Among the weather variables, RH max was positively correlated with the Oxycarenus spp. population, whereas Tmax, Tmin, Tmean, RH min and RH mean were highly significant and negatively associated. Continuous heavy rainfall with non-availability of opened bolls during third week of July has high negative impact on dusky population. Using pest-weather regression models, Oxycarenus spp. incidence on RCH 650, RS 2013 and LD 1019 may be forecasted with good accuracy i.e., R²=0.86, 0.89 and 0.87, respectively. In the third experiment, study on extent of loss caused by Oxycarenus spp. was carried on Bt cotton hybrid RCH 650 under screen house conditions with five treatments (0, 25, 50, 75 and 100 bugs per boll) replicated sixteen times. Bolls of uniform size were selected and covered with perforated net sleeves/cages to prevent natural incidence of Oxycarenus spp., later bugs were released into sleeves and left for 35-40 days. The results revealed that highest damage w.r.t boll weight, seed weight, 100 seed weight and germination was observed in 100 bugs per boll treatment, whereas lint staining (brownish) was very high in 75 and 100 bugs per boll treatment. It can be concluded from the above experiment that as the bug incidence per boll increases, the seed characters are severely affected. The fourth experiment on bio efficacy of homemade neem extracts against Oxycarenus spp. was carried out on Bt cotton hybrid US 51 and dusky cotton bugs along with natural enemies count were recorded (before spray, 3, 7, and 14 days after spray) twice during the entire cropping period. The results revealed that around 50 per cent reduction over control can be achieved by spraying neem formulations, indicating effective alternative approach to synthetic insecticides in pest management. Nimbecidine @ one litre per acre and homemade neem formulations @ 1.5 litre per acre were found effective against Oxycarenus spp. up to 7 days of spraying and neem formulations‟ effect on predators and especially spider population was found to be non-significant during the spray schedule.
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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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    Biology and management of molsari leaf webber, Nephopteryx eugraphella Ragonot (Lepidoptera : Pyralidae)
    (Punjab Agricultural University, 2023) Gurveer Singh; Sangha, K. S.
    Molsari (Mimusops elengi Linn.) is a large-sized ornamental tree with several medicinal properties. It is attacked by a number of insect-pests, the most important being the leaf webber- Nephopteryx eugraphella Ragonot. The larvae of N. eugraphella feed on leaves, apical shoots and flower buds, thereby giving a burnt appearance to the tree. In the present study, research on biology and management of molsari leaf webber, were carried out at Forest protection laboratory and forestry research area, Department of Forestry and Natural Resources, Punjab Agricultural University, Ludhiana, during 2021-2022. Biology was studied on molsari leaves with five generations (Generation I - Generation V) with a life span ranging between 32 to 45 days. Biological studies revealed that incubation period increased from 3.17 to 4.54 days, while the percent egg hatchability decreased from 90.83 to 72.99 per cent with increase in generation number. The mean duration of I, II, III and IV larval instars ranged between 2.96 to 3.92, 4.08 to 5.12, 3.56 to 4.96 and 4.69 to 5.40 days respectively during the different generations. The prepupal and pupal weight ranged between 47.20 to 55 mg and 45.20 to 60.60 mg. The length of I, II, III, IV, full grown larval instars; pre-pupa; pupa; adult female and adult male varied between 1.22 to 1.31, 4.18 to 4.48, 13.22 to 13.36, 19.22 to 19.88,19.40 to 21.61; 12.41 to 13.44; 9.72 to 10.88; 10.05 to 10.57 and 9.62 to10.32 mm respectively, whereas, breadth varied between 0.31 to 0.38, 0.46 to 0.67, 0.66 to 0.76, 0.66 to 1.11, 1.19 to1.51; 2.81 to 3.14; 2.97 to 3.23; 19.92 to 20.74 and 19.03 to 19.73 mm respectively. Duration of larval period, pre-pupa, pupa, adult female and adult male varied from 15.28 to 19.41, 0.60 to 2.11, 6.52 to 9.24, 6.00 to 9.38 and 3.86 to 6.33 days respectively. Interestingly, per cent survival of larva and pupa decreased in the successive generations. Additionally, sex ratio (male : female) ranged from 1:1.13 to 1:1.40. It was found that pre-mating, mating, pre-oviposition, oviposition and post-oviposition periods varied from 1.22 to 1.93, 0.42 to 0.62, 1.64 to 2.55, 2.28 to 3.62 and 2.08 to 3.21 days respectively. The larvae of N. eugraphella feed on leaves, apical shoots and flower buds, thereby giving a burnt appearance to the tree. Peak activity of the insect was recorded in the months of July, August and September with Tmax, RHm, RHe and rainfall showing significant positive correlation with insect infestation. Apis dorsata, Apis florea, Ischiodon scutellaris, Vespa orientalis were recorded as the casual visitors of molsari while among parasitiods Cotesia flavipes, Compislura sp, Eurytoma sp and Xanthopimpla sp were observed. Among predators, five Spiders (Marpissa mandala, Xysticus sp, Phidippus punjabensis, Rhene indicus and Sparassus sp) and one beetle (Parena nigrolineata) were recorded. Spinosad 48% SC (0.9 ml/l) proved to be the best treatment in suppressing the webs and larval population followed by Bacillus thuringiensis @ 4 g/l and Beauve ria bassiana @ 12 g/l.
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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.