Our previous studies have shown that some Trichoderma fungi trigger aggregation behavior in Formosan subterranean termites, Coptotermes formosanus Shiraki. However, the mechanisms underlying the induction of termite aggregation by Trichoderma fungi remain unclear. Here, we found that the aqueous or acetone extract of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg and Trichoderma virens Pers. ex Fries isolated from the gut or cuticle of C. formosanus elicited significant termite aggregation in 2‐choice tests. We then screened 9 Trichoderma metabolites (3‐acetoxy‐2‐butanone, phenol, 3‐ethoxypropionic acid, ethyl 2,4‐dioxovalerate, diglycolic acid, d ‐valine, styrene, 3‐aminopyridine, and hexyl acetoacetate) that triggered termite aggregation. Among them, phenol (1 000 μg/mL), 3‐ethoxypropionic acid (10 μg/mL), ethyl 2,4‐dioxovalerate (1 000 μg/mL), and diglycolic acid (1 000 μg/mL) showed the strongest activities, triggering termite aggregation throughout the 24‐h period. As T. asperellum and T. virens produce different metabolites that trigger aggregation behavior in termites, the mechanisms underlying the interaction between subterranean termites and Trichoderma fungi likely vary. Future studies are needed to test whether these chemicals can attract termites and increase bait consumption.

Repellants can be very useful in managing red imported fire ants, Solenopsis invicta Buren, particularly in some scenarios where application of synthetic insecticides is not appropriate. Our previous study showed that fire ants cannot transport food on surfaces treated with eugenol, and the repelling effect lasted for > 24 h, which motivated us to extend our research on eugenol derivatives. Herein, the electrophysiological effect, toxicity and repellency of five eugenol derivatives (methyl isoeugenol, eugenol acetate, isoeugenol, methyl eugenol, and isoeugenyl acetate) were evaluated against S. invicta workers. All eugenol derivatives triggered significantly higher EAG responses than the hexane blanks and had concentration-dependent toxicity against S. invicta workers. All tested eugenol derivatives except isoeugenyl acetate showed strong repellency by significantly decreasing the number of defending (aggression mode) and foraging (non-aggression mode) ants in the tested arenas . Unexpectedly, methyl isoeugenol almost repelled all defending fire ants from disturbed mounds. This compound also repelled foraging ants significantly longer than eugenol. At the concentration of 50 mg/kg in sand, methyl isoeugenol was the only tested compound that completely suppressed the digging behavior of S. invicta workers. In addition, fire ants exhibited low levels of nesting behaviors in flowerpots containing sand treated with each eugenol derivative (500 mg/kg). Surprisingly, the repellency of methyl isoeugenol in flowerpots containing treated sand could last for almost one month. Our study may bring an opportunity to develop strong and long-lasting fire ant repellant products against foraging, defending, and nesting fire ants.