Combined meteorological, atmospheric stability and spray volume effect on the control of Spodoptera frugiperda (Lepidoptera: Noctuidae) in maize

Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), is the most important maize pest in Brazil and can cause major yield losses. This study aimed determine which the most favorable meteorological and atmospheric stability conditions are for obtaining maximum control effectiveness of S. frugiperda in maize in insecticide applications with different spray volumes. An insect pest natural infestation field experiment was carried in the 2018/2019 season. Spinetoram (12 g a.i. ha-1) was applied three times along the crop cycle. The experimental design was in blocks with nine treatments and four replicates within each block, besides the maintenance of a control treatment without application, totaling 10 treatments. The evaluated factors were the atmospheric condition represented by three times of application (TOA: 8AM, 2 and 6PM) and three spray volumes (SV: 200, 300 and 400 L ha-1). S. frugiperda foliar feeding damage was evaluated using a numerical scale score. Meteorological conditions at the time of application and SV interfered in the pest control effectiveness. Lowest average damage scores were observed in applications carried out at 8 am, when the air and dew point temperatures were lower, and the relative humidity and wind velocity were higher than at 2 pm and 6 pm, and with SV of 400 L ha-1. For the most efficient treatment (8 am - 400 L ha-1) applied at 12/27/2018, the atmosphere was stable.