BIO-ECOLOGY AND MANAGEMENT OF STEM BORER, Chilo partellus Swinhoe INFESTING MAIZE
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Date
2005
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AAU, Anand
Abstract
Investigations on bio-ecology and management of Chilo partellus Swinhoe infesting maize were carried out at B. A. College of Agriculture, Anand Agricultural University, Anand during 2003 to 2004 in kharif season. It is an important pest of maize causing severe damage in middle Gujarat conditions. Of the plant flora surveyed for the host range of C partellus, sorghum and bajra were found as hosts of this pest in this region. The newly hatched larvae feed on the leaves of the central whorl. Here it mines the sheath and often tunnels inside the midrib. The older larvae bore down inside the funnel of the plant and feed on internal tissues of stem which caused 'dead hearts'. Their course from the leaf to stem was interspersed with small punctures on the leaf. The early instar larvae also feed on tassels. The female moths laid the eggs in clusters usually on lower surface of leaves near the midrib and sometimes on upper surface of leaves. The freshly laid eggs were creamy white in colour and ultimately become black before eclosion. It was oval in shape and overlapping each other in rows. The length and breadth of eggs were 0.98 + 0.07 and 0.68 + 0.03 mm, respectively. The incubation period was 3.42 + 0.53 days with hatching per cent of 63.47 + 12.29. The caterpillars passed through six larval instars. First instar larva was orange with black head. Three pairs of thoracic legs and four pairs of prolegs were present. Nine pairs of spiracles situated on the prothoracic and first eight abdominal segments were visible. Bands of deep orange colour were present on each segment. Small dark hairs were present on each segments give a spiny appearance to the body. The body colour of second instar larva becomes slightly darker than that of first instar larva. There was one dark line running laterally on either side of the prothorax to the anal segment. The prothoracic segment was darker in colour than the remaining segment. The third instar larva was stout bodied and darker than the second instar larva. The antennae were visible and the dark spot from which the hairs arise become darker than that of the second instar larva. The lateral dark lines on either side of the larva disappear and spiracle becomes very prominent. The fourth instar larva was light brown in colour with dark brown head. The prothoracic shield was very prominent. The thoracic as well as abdominal segments have some scattered tubercles each with one, two or even three setae and spiracles were well developed. The fifth instar larva resembles the fourth instar larva except that the tubercles were quite prominent. The sub-dorsal stripes, one on either side were present along the body length of the larva. The head was reddish brown in colour and prothoracic shield was light brown in colour. The sixth instar larva was quite different from fifth instar larva. The tubercles were larger. The sub-dorsal stripes disappear. Prothoracic shield was dark brown in colour and body was dirty white. Posterior region of each segment appears white. The duration of first, second, third, fourth, fifth and sixth instar larva was 3.70 + 0-70, 4.13 ± 0.94, 2.91 ± 0.79, 4.17 + 1.07, 4.00 ± 1.01 and 3.96 ± 1.12 days. respectively. The total larval period was 21.80 + 3.73 days. Length of the first, second, third, fourth, fifth and sixth instar larva was 1.84 + 0.37,4.51 + 0.33, 7.73 ± 0.48,13.13 + 0.95, 16.97 + 0.73,22.80 + 0.40 mm, whereas the breadth was 0.21 + 0.04, 0.69 ± 0.06, 0.97 ± 0.10, 1.66 + 0.07, 2.61 + 0.12 and 3.13 ± 0.10 mm incase of breadth, respectively. The duration of pre-pupae was 1.96 ± 0.56 days. The length, breadth and width of head capsule was 15.70 ± 0.40, 3.38 ± 0.31 and 2.25 ± 0.34 mm, respectively. The pupation took place within the maize stem in a chamber constructed by the mature larva. Pupa was creamy yellow when freshly formed and turned reddish brown subsequently. It possessed six spines arranged in two rows at the tip of the abdomen. The length of male and female pupa was 11.21 + 0.18 and 14.78 + 0.07 mm, whereas breadth was 2.44 + 0.04 and 3.05 + 0.03 mm, respectively. The distances between genital and anal pore for male and female was 0.23 + 0.03 and 1.14 + 0.02 mm, respectively. The duration of male and female pupa was 4.12 + 0.95 and 4.23 + 1.42 days, respectively. The moth was straw coloured with fore wings slightly darker than the hind wing and a pair of prominent palpi projecting in front of the head like a beak. The longevity of male and female adult was 3.07 + 0.64 and 3.43 + 0.62 days, respectively. The length of male and female moth was 9.90 + 0.31 and 13.45 + 0.79 mm, while the breadth with expanded wing was 20.29 ± 0.21 and 27.21 + 0.56 mm, respectively. The pre-oviposition, oviposition and post-oviposition periods were noted as 1.75 + 0.50, 1.25 ± 0.50 and 0.75 ± 0.95 days, respectively. The fecundity was 19.57 ± 9.50 eggs per female. The sex ratio (male : female) under field and laboratory conditions was 1 : 1.18 and 1 : 1.21, respectively. The total life span for male and female was 34.69 + 2.09 and 35.06 + 2.56 days, respectively. The incidence of the pest begins from 1st week of July and continued up to 2nd week of September with a peak activity in August. Parasite Apanteles flavipes showed significant positive correlation with number of larval population during both the years. The abiotic factors, sunshine hrs and rainfall had significantly negative and positive association with C. partellm on maize during 2004, respectively. . Among the 20 varieties/genotypes screened, Ganga Safed 2, Narmada Moti and GM 3 were found resistant to C. partellus. and registered higher grain yield. Of the five indigenous plant materials, five azadirachtin based formulations and eleven synthetic insecticides evaluated against C. partellus larvae infesting maize, Neemark (2.50 %), NeemAzal-F (0.015 %), neem seed kernel extract (5 %), carbofiiran, phorate and cartap (10 kg/ha) performed better to protect the maize from infestation of C partellus. Among the botanicals, Neemark treated plots registered highest (23.90 q/ha) grain yield followed by NeemAzal-F (23.66 q/ha) and NSKE (22.67 q/ha). In the above treatments, yield increase over control ranged between 40.37 and 47.98 per cent, whereas avoidable losses were upto 5.14 per cent. The effective botanicals NSKE, NeemAzal-F and Neemark recorded 1 : 1.66,1 : 1.01 and 1 : 0.61 NICER, respectively. Of the synthetic insecticides, carbofiiran treated plots produced highest (27.47 q/ha) grain yield followed by phorate (27.25 q/ha) and cartap (26.90 q/ha). Increase in yield over control in these treatments varied from 61.66 to 65.08 per cent, whereas avoidable losses were upto 2.07 per cent. The NICBR was calculated as 1 : 2.50, 1 : 3.10 and 1 : 2.57 for the effective treatments of carbofiiran, phorate and cartap, respectively.
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Keywords
AGRICULTURAL ENTOMOLOGY, AGRICULTURE, MANAGEMENT