Toxicity test of compound essential oil nanoemulsion on fall armyworm ( <i>Spodoptera frugiperda</i> J.E. Smith) eggs

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is one of the world’s most destructive and costly pests. Its larvae can attack more than 80 crop species including corn. FAW control efforts that have been carried out by most of our farmers involve synthetic pesticides. The development of plant pesticides with essential oil (EO) base materials is becoming increasingly innovative through nanoemulsion technology. This study aimed to determine the effective concentration/dose of the compound EO nanoemulsion (CEoNE) formula against FAW egg mass. The research was carried out from August to December 2023. FAW egg masses were collected daily in the screen house and brought to the laboratory to count the number of eggs in one egg mass under a stereo microscope. Preliminary tests were conducted to determine whether the right dose affects egg mortality. The results of preliminary tests on the dose of CEoNE showed that at a concentration of 15 ml/L, the average percentage of mortality of FAW egg groups reached more than 60% for 1-, 2- and 3-d-old FAW egg masses. These test results revealed that the concentrations of the CEoNE formula that would be further tested for FAW egg mortality were 11, 12, 13, 14 and 15ml/L to determine the LC50. The results show that, compared with the other treatments, the dose of 13.6 ml/L CEoNE is more effective against 3-d-old egg masses, which indicates that CEoNE has an ovicidal effect on S. frugiperda.