Population dynamics of major insect-pests of pigeonpea (Cajanus cajan (L.) Millsp.) and assessment of avoidable yield losses due to them
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Date
2017
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CCSHAU
Abstract
Field studies on “Population dynamics of major insect-pests of pigeonpea (Cajanus cajan (L.)
Millsp.) and assessment of avoidable yield losses due to them” was carried out during kharif 2016.
Population dynamics of major insect-pests (E. kerri, M. vitrata, H. armigera, C. gibbosa and M.
obtusa) of pigeonpea was studied on four varieties of pigeonpea viz., Paras, AL 201, Manak and PAU
881. The incidence of E. kerri started from 29th SMW to 44th SMW with a peak during 33rd
SMW (3.83 nymphs/three leaves/plant). Population of M. vitrata larvae, H. armigera larvae, C.
gibbosa nymphs and C. gibbosa adults first appeared in 38th SMW (flowering) with peak activity
during 40th SMW (0.50 larvae/plant), 44th SMW (0.39 larvae/plant), 47th SMW (0.36 nymphs/plant)
and 40th SMW (4.08 adults/plant), respectively. Maximum number of web formed by M. vitrata larvae
and egg masses laid by C. gibbosa was found 2.29 webs/plant (40th SMW) and 0.59 egg masses/plant
(38th SMW), respectively. Incidence of M. obtusa first appeared during 41st SMW with a peak in 45th
SMW (3.08 % pod damage). Population of M. vitrata larvae disappeared in 42nd SMW while that of H.
armigera, C. gibbosa and M. obtusa prolonged to harvesting of the crop (48th SMW). Non-significant
impact of all weather parameters was observed on incidence of E. kerri and H. armigera. Significant
and negative correlation found between M. vitrata and sunshine hours; M. obtusa and sunshine hours;
C. gibbosa nymphs and temperature. Significant and positive correlation found between C. gibbosa
adult and temperature, rainfall; C. gibbosa egg masses and temperature; M. obtusa and morning
relative humidity. Total pod damage caused by different insect-pests studied ranged from 27.78 to
39.50 per cent. The grain yield of different varieties ranged from 7.94 to 10.52 q/ha.
For the assessment of yield losses, variety Manak was sown on paired plots. Spraying was
done in protected plots with dimethoate 30 EC (first spray) and deltamethrin 2.8 EC (second and third
spray) when the insect-pests crossed economic threshold (ET). The avoidable loss in grain yield was
28.37 per cent, while the reduction in pod damage in protected plots over unprotected plots was 45.91
per cent.
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