Diversity, seasonal incidence and damage assessment of Oxycarenus spp. on cotton

Noor Mahammed N R

Diversity, seasonal incidence and damage assessment of Oxycarenus spp. on cotton

Date

2023

Authors

Noor Mahammed N R

Publisher

Punjab Agricultural University

Abstract

The study on „Diversity, seasonal incidence and damage assessment of Oxycarenus spp. on cotton‟ was conducted at PAU, RRS Faridkot during Kharif 2022-23. Increasing incidence and damage incurred due to dusky cotton bug on cotton during the last few years necessitated to conduct the present study in north India. The results of first experiment were based on collection of dusky cotton bug samples from 31 locations spread across three states of Punjab, Haryana and Rajasthan and revealed that mt-COI gene based molecular identification doesn‟t confirm Oxycarenus at species level. The second experiment on seasonal incidence of dusky cotton bug was recorded on Bt cotton hybrid G. hirsutum RCH 650, non Bt G. hirsutum var. RS 2013 and G. arboreum var. LD 1019 at weekly intervals from 20 randomly selected plants (five squares/flowers/bolls) from each cultivar starting from the appearance of bugs (June) till the harvest of the crop (December). The results revealed that population of Oxycarenus spp. started during square formation stage (July last week), reached peak (around 100 bugs per 5 bolls) during complete boll opening stage (November second week) and remained present till the harvest of crop. Among the weather variables, RH max was positively correlated with the Oxycarenus spp. population, whereas Tmax, Tmin, Tmean, RH min and RH mean were highly significant and negatively associated. Continuous heavy rainfall with non-availability of opened bolls during third week of July has high negative impact on dusky population. Using pest-weather regression models, Oxycarenus spp. incidence on RCH 650, RS 2013 and LD 1019 may be forecasted with good accuracy i.e., R²=0.86, 0.89 and 0.87, respectively. In the third experiment, study on extent of loss caused by Oxycarenus spp. was carried on Bt cotton hybrid RCH 650 under screen house conditions with five treatments (0, 25, 50, 75 and 100 bugs per boll) replicated sixteen times. Bolls of uniform size were selected and covered with perforated net sleeves/cages to prevent natural incidence of Oxycarenus spp., later bugs were released into sleeves and left for 35-40 days. The results revealed that highest damage w.r.t boll weight, seed weight, 100 seed weight and germination was observed in 100 bugs per boll treatment, whereas lint staining (brownish) was very high in 75 and 100 bugs per boll treatment. It can be concluded from the above experiment that as the bug incidence per boll increases, the seed characters are severely affected. The fourth experiment on bio efficacy of homemade neem extracts against Oxycarenus spp. was carried out on Bt cotton hybrid US 51 and dusky cotton bugs along with natural enemies count were recorded (before spray, 3, 7, and 14 days after spray) twice during the entire cropping period. The results revealed that around 50 per cent reduction over control can be achieved by spraying neem formulations, indicating effective alternative approach to synthetic insecticides in pest management. Nimbecidine @ one litre per acre and homemade neem formulations @ 1.5 litre per acre were found effective against Oxycarenus spp. up to 7 days of spraying and neem formulations‟ effect on predators and especially spider population was found to be non-significant during the spray schedule.

Citation

Noor Mahammed N R (2023). Diversity, seasonal incidence and damage assessment of Oxycarenus spp. on cotton (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.