Investigations on Damaging Potential of Chilo partellus Swinhoe and Standardization of Multiplication Technique of Cotesia flavipes Cameron in Southern Rajasthan
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Date
2011
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MPUAT, Udaipur
Abstract
The “Investigations on Damaging Potential of Chilo partellus Swinhoe and Standardization of Multiplication Technique of Cotesia flavipes Cameron in Southern Rajasthan” were carried out at Instructional Farm and Maize Entomology Laboratory, Department of Entomology of Rajasthan College of Agriculture, Udaipur, Rajasthan during kharif 2008 and 2009. The data recorded on Leaf Injury Rating (LIR) on HQPM-1 and African tall after release of varied number of neonate stem borer larvae, 4 to 32 / plant, clearly express the difference in the resistance potential of cultivar. The cultivar HQPM-1 could shown the resistance against 20 larvae / plant by giving LIR 5.81 and 5.90 during 2008 and 2009 respectively while African tall could tolerate only 8 larvae / plant by recording 5.36 and 5.19 LIR during 2008 and 2009 respectively. Further release of 24 to 32 larvae / plant in HQPM-1 resulted in varied LIR, 6.87 to 8.92 in 2008 and 6.76 to 8.89 in 2009, wherein African tall gave 8.93 to 9.00 LIR during test years. Increase in number of larvae released also had significant effect on plant height wherein drastic reduction was observed after release of 20 larvae / plant in African tall compared to HQPM-1. Maximum tunnel numbers 1.40 and 1.33 per plant in HQPM-1 were recorded with release rate of 24 larvae / plant while in African tall it was 2.37 and 2.36 during 2008 and 2009 respectively at the release rate of 16 larvae / plant. The longest tunnel length (9.29 and 8.43 cm) was observed with release of 24 larvae/ plant during 2008 and 2009 respectively in HQPM-1 while in African tall tunnel length increased from 4.61 to 15.32 cm per plant with gradual increase in number of larvae that is 4 to 16 per plant in 2008. Similarly in 2009 it ranged from 6.14 to 15.19. The data showed gradual increase of tunnel length up to release of 24 larvae / plant and thereafter dead hearts were received. Minimum plant yield in HQPM-1 was 7.58 and 7.10 g / plant was obtained after release of 32 larvae / plant during 2008 and 2009, respectively whereas in African tall 0.00 g / plant minimum yield was observed after release of 24 larvae/plant during 2008 and 2009. The results showed gradual decrease in yield with increase in number of larvae released / plant. All treatments were significantly different to each other.
The correlation between yield and the combined effect of independent variables viz. LIR, plant height, tunnel number and tunnel length on yield during 2008 and 2009 was highly significant with R=0.993 and 0.995 in HQPM-1 and R=0.983 and 0.999 in African tall during 2008 and 2009 respectively. Correlation between LIR and plant height of HQPM-1 and African tall showed significant negative correlation. Correlation between LIR and tunnel number as well as LIR and tunnel length was negative but non significant. The observations recorded on correlation between LIR and yield in test corn showed highly significant negative correlation in HQPM-1 (r = -0.983 and -0.982) and in African tall (r =-0.945 and -0.989) during 2008 and 2009 respectively which expressed that increase in the LIR decreased the yield. Plant height and tunnel number as well as plant height and tunnel length in HQPM-1 and African tall showed positive correlation but non significant in HQPM-1 while significant in African tall. The data obtained on plant height and yield of HQPM-1 (r = 0.978 and 0.985) and African tall (r = 0.839 and 0.907) showed highly significant positive correlation during 2008 and 2009, respectively. Tunnel number and tunnel length showed highly significant positive correlation in HQPM-1 r = 0.955 and 0.959 and in African tall r = 0.996 and 0.985 during 2008 and 2009 respectively. The correlation between tunnel number and yield as well as tunnel length and yield was found non significant.
The preference of 17 and 20 days old larvae of C. partellus for parasitization by C. flavipes were highest where maximum parasitization, 82.61 and 82.46 per cent and 43.09 and 42.70 cocoons respectively were obtained. A significant positive relationship between ages of host larvae and parasitization as well as host age and number of cocoons was obtained while sex ratio did not affected by larval age. Parasitization and number of cocoons in different sized ovipositional chamber showed that maximum parasitization, 89.56 per cent and maximum cocoons 37.53 were recorded in test tube. The sex ratio recorded in test tube was statistically superior to pearl pet jar of 1000 and 2000 g but at par with pearl pet jar of 500 g. The increase of larval density from 2 to 5 larvae to single pair of adult parasitoid in different ovipositional chamber showed the distribution of egg laid which resulted in decreased parasitization, number of cocoons formed and sex ratio.
Storage of cocoons for 10 days at different test temperatures did not affected adult emergence significantly and emergence ranged from 95.96 to 97.58 per cent. Adult emergence decreased gradually with the increase of storage especially at low temperature (5°C). The sex ratio obtained from the emerged adult showed that low temperature (5°C) significantly affects the sex ratio. Highest sex ratio, 0.85, and maximum cocoons (47.08) were observed when cocoons stored for 10 days at 20°C while 5°C temperature inhibited the growth and development with least number of cocoons.
Description
Investigations on Damaging Potential of Chilo partellus Swinhoe and Standardization of Multiplication Technique of Cotesia flavipes Cameron in Southern Rajasthan
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Citation
Manjoo and Bajpai, 2011