Biology, predation potential and population dynamics of ladybird beetle, Coccinella septempunctata L. on wheat aphid, Rhopalosiphum maidis Fitch
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Date
2019
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CCSHAU
Abstract
Biology and feeding potential of Coccinella septempunctata L. on Rhopalosiphum maidis (F.) was studied at 25±1o C, 65±5%, 16:8 L:D and room temperature, while the population dynamics of R. maidis and C. septempunctata was studied under field conditions. The average incubation period of C. septempunctata was 3.30 and 4.00 days with 82 and 97 per cent hatchability at 25±1o C, 65±5%, 16:8 L:D and room temperature, respectively. The predator passed through four larval instars. On an average 1st, 2nd, 3rd and 4th instar lasted for 2.71±0.12, 1.90±0.08, 2.27±0.96 and 4.88±0.11 days, respectively at 25±1o C, 65±5%, 16:8 L:D. The corresponding figures at room temperature were 3.01±0.12, 2.10±0.09, 2.61±0.07 and 5.71±0.10 days, respectively. The total larval period was recorded to be 11.75±0.19 and 13.43±0.21 days at 25±1o C, 65±5%, 16:8 L:D and room temperature, respectively. Average pupal period at 25±1o C, 65±5%, 16:8 L:D was 5.00±0.52 days. On an average, adult females lived for 42.0±3.972 and 38.7±3.80 days at 25±1o C, 65±5%, 16:8 L:D and room temperature, respectively, while the longevity of male at the respective temperature was 33.60±3.72 and 30.80±3.80 days, respectively. A female laid 372 eggs at 25±1o C, 65±5%, 16:8 L:D, while it laid 339 eggs at room temperature.
Both grub and adult were found voracious predator on R. maidis. The 4th instar grub consumed on an average of 121.50, 163.50, 189.30 and 197.87 aphids per grub when provided with 150, 200, 250 and 300 aphids per grub, respectively. Adult female on average consumed 112.20 aphids per day while male consumed 84.20 aphids per day. Mid-February to mid-March (7th to 11th SMW) was the most favorable period for multiplication of the aphids, and the peak aphid population of 23.00 aphids/shoot reached by first week of March. The aphid population declined suddenly in the last week of March and disappeared completely in the first week of April. The C. septempunctata population appeared during first week of March (10th SMW) and reached its peak in last week of March (13th SMW). Study on field efficacy revealed that effectiveness of treatment in order was thiamethoxam 25 WG followed by Neemastra, quinalphos 25 EC, M. anisopliae, B. bassiana and V. lecanni at 15 days of after spray. Bio-efficacy of these insecticides and bio-pesticides under laboratory conditions was also evaluated by leaf dip bioassay method which revealed that thiamethoxam 25 WG and quinalphos 25 EC were the only effective treatment in which 100 per cent mortality of aphid was observed at 72 hours after treatment but these were highly toxic to C. septempunctata while the bio-pesticides were quite safe.
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