A new method for screening Solenopsis invicta repellents based on Y-type repellent measuring ruler

Screening and testing methods plays a crucial role in developing effective repellents against the red imported fire ant, Solenopsis invicta Buren. Currently it lacks reliable methods for evaluating repellent activity against S. invicta with a high attack level. In this study, a self-developed Y-type repellent measuring ruler was used to monitor the activity patterns of S. invicta workers. The effects of naked-arm and bandaged-arm of Y-type repellent measuring ruler on the number of climbing workers were compared. Additionally, the repellent activity of DEET (N, N-diethyl-meta-toluamide) against S. invicta workers was measured. The results indicated that the arm length of the Y-type measuring ruler was negatively correlated with the density of S. invicta, and a Y-type repellent measuring ruler with an arm length of 11 cm was selected for subsequent repellent testing. Under laboratory conditions, the number of S. invicta workers increased significantly within 75 s after being disturbed; while in the field, the number of S. invicta workers peakedat 30 s after being disturbed. There was no significant difference in the number of workers between the naked and bandaged Y-type repellent measuring rulers at different time points (P > 0.05). DEET exhibited significant repellency against S. invicta workers, with both the repellent rates and effective repellency durations exhibiting a positive correlation with treatment concentration. The repellent rates of the naked and bandaged Y-type measuring rulers reached 100% at concentrations of 5.0% and 10.0%, respectively. When the DEET concentration was 5.0%, the effective repellency durations of the naked and bandage measuring rulers were 198.16 min and 228.14 min, respectively. The Y-type repellent measuring ruler designed and optimized in this study can directly determine the repellent activity of compounds against S. invicta under disturbed conditions. It provides a new method for screening and evaluation S. invicta repellent agents, and also offers technical support for the development of individual protective agents against this invasive ant species.