BIONOMICS, POPULATION DYNAMICS AND MANAGEMENT OF LEAF WEBBER, Orthaga euadrusalis Walker IN MANGO, Mangifera indica L.
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Date
2004
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AAU, Anand
Abstract
Investigations on bionomics, population dynamics and management of Orthaga euadrusalis Walker infesting mango were carried out at B. A. College of Agriculture, Anand Agricultural University, Anand Campus, Anand during 2002-03 to 2003-04. It is an important pest of mango causing severe damage in middle Gujarat conditions. The newly hatched caterpillars feed gregariously on leaf chlorophyll by scraping the leaf surface. The advance stages web the leaves together and live within it and feed voraciously on leaves. The tents (webs) were clearly visible from a distance on attacked mango trees. The female moth laid eggs singly or in clusters on lower surface of leaves, occasionally on tender mango twigs. The eggs were greenish dull, oval and flattened. The length and breadth of eggs were 0.86 + 0.04 and 0.58 + 0.06 mm, respectively. The incubation period was 4.29 + 0.47 days with hatching per cent of 93.03 ±4.51. The leaf webber passed through seven larval instars. The first instar larvae were pale green to light yellow in colour with shining brownish head. A pink transverse band on first abdominal segment, four brownish longitudinal streaks and several scattered thin white hairs were found on lateral part of the body. The second instar larvae were similar to the first instar larvae in its general appearance and colour except having brown head with dark brown spots and black to brown prothoracic shield. The third instar larvae were also similar to the earlier instar larvae in its colour except morphological characters. On lateral side, it has single light green longitudinal line and pink transverse band on first abdominal segment was become indistinct. The larvae of the fourth instar did not show any remarkable change except the pink coloured transverse band on first abdominal segment disappeared completely. The fifth instar larvae were dark greenish black in colour and small white seta was arised at dorsal region on either side of mid dorsal line. The sixth instar larvae were similar to earUer instar except morphological characters. The colour of longitudinal stripes change to green in this instar. The full grown seventh instar larvae were pale greenish to black in colour with two broad dark green longitudinal stripes. The duration of the first, second, third, fourth, fifth, sixth and seventh instar larvae was 4.16 ± 0.68, 4.68 ± 1.13, 3.48 ± 0.74, 3.58 ± 1.21, 3.86 ± 1.40, 4.18 ± 1.19 and 5.76 + 1.70 days, respectively. The average larval duration was 29.70 + 3.77 days. The length of the first, second, third, fourth, fifth, sixth and seventh instar larvae was 1.34±0.18,4.55±0.78,6.67±0.44,10.98 ±1.13,16.84 ±1.14,20.80± 1.26 and 27.12 ± 1.94 mm, whereas it was 0.29 ± 0.02, 0.46 ± 0.04, 0.95 ± 0.21, 1.64 ± 0.12, 2.26 ± 0.13,2.65 ± 0.12 and 3.55 ± 0.33 mm in case of breadth, respectively. The width of head capsule for corresponding instar was 0.29 ± 0.04, 0.56 ± 0.04, 0.72 ± 0.05, 1.16 ± 0.22, 1.94 ±0.11,2.34 ± 0.10 and 3.26 ± 0.24 mm, respectively. The pre-pupae were pale greenish to dark black in colour. The duration of prepupae was 3.84 ± 1.25 days. The length and breadth was 21.08 ± 1.36 and 3.50 ± 0.40 mm, respectively. The pupation took place within the web, inside the silken cocoon. The pupae were dark brown in colour. The length of male and female pupae were 13.04 ± 0.68 and 13.80 ± 0.71 mm, respectively, whereas breadth was 3.76 ± 0.44 and 3.88 ± 0.33 mm, respectively. The distance between genital and anal pore for male and female was 0.42 + 0.06 and 1.09 + 0.13 mm, respectively. The duration of male and female pupae were 15.8 + 2.47 and 17.16 + 3.55 days, respectively. Adults of O. euadrusalis were brownish grey with wavy lines on forewings. Hindwings were ashy grey with fringed apical margin. The longevity of male and female was 4.00 + 0.82 and 8.3 + 0.68 days, respectively. The length of male and female was 12.12 + 0.67 and 13.0 + 0.82 mm, respectively, while the breadth with wing expanded was 25.36 +1.08 and 27.76 + 1.33 mm, respectively. The pre-oviposition, oviposition and post-oviposition period noted as 3.30 + 0.82, 3.70 ± 0.82 and 1.30 + 0.48 days, respectively. The fecundity of female was 63.00 + 20.14 eggs. The sex ratio under field condition was 1 : 1.18 and in laboratory was 1 : 1.14. The total life span for male and female was 56.6 + 6.95 and 59.6 + 7.49 days, respectively. The incidence of the pest began from end of March and continued up to third week of January with a peak activity in November. The activity of the pest during both the years showed significantly negative association with wind speed, temperature and vapour pressure. Among the 18 cultivars Rajapuri, Kesar, Langdo and Dashehari were found most preferred, whereas Amrapali, Dadamiyo, Jamadar, Mallika, Malgoa, Karanjiyo, Neeleshwari, Sardar and Vanraj were not preferred by O. euadrusalis larvae. Among the six indigenous plant materials, three azadirachtin based formulations, one microbial formulation and eleven synthetic insecticides evaluated against O. euadrusalis larvae infesting mango, neem seed kernel extract (5 %) and NeemAzal-F (0.015 %) were found effective and economical, which costed 890 to 1321 Rs/ha. However, Gronim (0.5 %), Vanguard (0.5 %) and Biolep (0.015 %) were also found effective but cost of application was too high (above 2200 Rs/ha). The treatments of synthetic insecticides such as quinalphos (0.05 %), monocrotophos (0.04 %), cypennethrin 3 % + quinalphos 20 % (0.023 %) and cypermethrin (0.01 %) effectively checked the O. euadrusalis incidence. These treatments costed 665 to 1325 Rs/ha. Carbaryl was found highly effective but cost of treatment was above 2100 Rs/ha. The treatments of neem leaf extract (5 %), neem oil (0.5 %), profenophos (0.05 %), fenvalerate (0.01 %) and malathion (0.05 %) were found inferior against the pest. Tlie microbial formulations Halt and Biolep (B. thuringiemis) @ 2 g/1 and Biosofl (B. bassiana) @ 3-4 g/1 were found highly effective, whereas Vertisoft (V. lecani) @ 2-4 g/1 and Biolep (B. thuringiemis) @ 1 g/1 performed poor in killing the O. euadrusalis larvae in laboratory condition.
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AGRICULTURAL ENTOMOLOGY, AGRICULTURE, A STUDY