Impact of Agro-Ecological Factors on the Dynamics of Sucking Insect Pests Population on Okra, Abelmoschus esculentus (L.) Moench

Abstract

Aims: To correlate population of major sucking insect pests on okra with the predator and abiotic factors, i.e., the minimum & maximum temperature, relative humidity and rainfall. Study Design: Five separate plots of 2.25 x 1.5 m2 size keeping row to row and plant to plant distance of 45 cm and 30 cm, respectively were maintained. Place and Duration of Study: The investigations were carried out in Kharif, 2022 at Horticulture farm, S.K.N. College of Agriculture, Jobner. Methodology: The Pusa Bhindi-5 variety of okra was sown on 14th July, 2022 and recommended package of practices were adopted for raising the crop excluding plant protection measures. The observations on insect pest populations (leafhopper and whitefly) were recorded on five randomly selected and tagged plants in each plot at weekly interval and simple correlation was computed between mean observations of pest populations, natural enemies and meteorological parameters.    Results: The infestation of leafhopper and whitefly on the okra crop began on 15th August (33rd SMW). Peak populations of leafhoppers (30.28 per three leaves) were observed in the third week of September (38th SMW), with minimum and maximum temperatures of 21.1°C and 33.1°C, respectively, and relative humidity at 50%. Whitefly populations (17.84 per three leaves) peaked in the second week of September (37th SMW) when the minimum and maximum temperatures were 21.5°C and 34.7°C, respectively, and relative humidity was 45%. The correlation analysis revealed a non-significant relationship between leafhopper populations and the following abiotic factors: minimum temperature (r = 0.42), relative humidity (r = -0.34), and rainfall (r = -0.51). However, a significant positive correlation was found between leafhopper populations and maximum temperature (r = 0.63), as well as with the ladybird beetle Menochilus sexmaculatus (r = 0.80) at a 5% significance level. For whitefly populations, non-significant correlation was observed with the set of abiotic factors: maximum temperature (r = 0.61), minimum temperature (r = 0.54), relative humidity (r = -0.30), and rainfall (r = -0.50). A significant positive correlation was noted between whitefly populations and the ladybird beetle M. sexmaculatus (r = 0.79) at the 5% significance level. Conclusion: The study reveals that leafhopper and whitefly populations on okra are positively correlated with maximum temperature and the presence of the ladybird beetle Menochilus sexmaculatus. However, abiotic factors like minimum temperature, relative humidity and rainfall have minimal influence on pest populations, emphasizing the role of natural predators in pest management.