Seasonable abundance of beet armyworm Spodoptera exigua (Hubner) infesting Onion with weather factors in Madurai district of Tamil Nadu
Arulkumar G, Manisegaran S, Nalini R and Mathialagan M
The periodical field surveys were carried out from August 2014 to April 2015 (Season I: Aug to Dec’2014; Season II: Jan to Apr’2015) in five different locations in the farmer’s holdings in and around Madurai district. Regardless of the seasons and locations surveyed, S. exigua (Hub.) was observed as major insect pests on the onion. The damage by Spodoptera exigua was the lowest (8.5%) during the second week of August 2014, reached the maximum of 33.4 per cent during the fourth week of October 2014. Thereafter, it increased gradually and attained the maximum during the first week of October 2014. Later, it declined from the first week of November 2014 onwards. The second peak damage was observed 22.2 per cent during the first week of February 2015 and it was gradually declined from the third week of February 2015. Correlation between mean damages of S. exigua and weather factors indicated that the maximum and minimum temperatures showed a significant negative correlation, while the relative humidity exhibited a positive correlation. But rainfall had no effect.
Arulkumar G, Manisegaran S, Nalini R, Mathialagan M. Seasonable abundance of beet armyworm Spodoptera exigua (Hubner) infesting Onion with weather factors in Madurai district of Tamil Nadu. J Entomol Zool Stud 2017;5(6):1157-1162.