Location: Biological Control of Pests ResearchTitle: Insecticidal and enzyme inhibitory activities of Isothiocyanates against Red Imported Fire ants, Solenopsis invicta
Submitted to: Biomolecules EISSN 2218-273X
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2020
Publication Date: 5/5/2020
Citation: Du, Y., Grodowitz, M.J., Chen, J. 2020. Insecticidal and enzyme inhibitory activities of Isothiocyanates against Red Imported Fire ants, Solenopsis invicta. Toxicon. pp. 1-10.
Interpretive Summary: The red imported fire ant is significant invasive pest that affects humans, wildlife, crops, and livestock. Fire ant control has depended heavily on the use of synthetic insecticides, which causes a concern on their negative impacts in the environment. Naturally occurring compounds are a source of new chemistry for developing control products that are more environmentally friendly, due to their rapid environmental biodegradable property and potential lower toxicity to natural enemies, humans and other mammals. Various isothiocyanates occur in plants and other organisms. Insecticidal property of certain isothiocyanates have been reported; however, toxic effect of isothiocyanates against fire ants has never been investigated. In this study, three isothiocyanates found in Bagrada bugs were assessed for their contact and fumigation toxicity against fire ants and their effect on three enzymes in fire ants were also assessed. Due to their high toxicity to fire ants, there is a great potential for their application in fire ant control.
Technical Abstract: Four isothiocyanates (ITCs) including allyl isothiocyanate (AITC), 3-buten-1-yl isothiocyanate (3BITC), 3-(methylthio) propyl isothiocyanate (3MPITC), and 2-phenylethyl isothiocyanate (2PEITC) and were identified from Bagrada bugs, Bagrada hilaris. In this study, contact and fumigation toxicities of three ITCs (AITC, 3MPITC, and 2PEITC) were evaluated against the red imported fire ant worker, Solenopsis invicta. 2PEITC and 3MPITC exhibited strong contact toxicity. The LD50 value of AITC, 2PEITC and 3MPITC were 7.99, 2.36, and 2.09 µg/ant respectively. In addition, AITC and 3MPITC also showed strong fumigation toxicity, but not 2PITC. The LC50 values of AITC, and 3MPITC were 32.49 and 57.6 µg/L, respectively. Furthermore, esterase (EST), glutathione S-transferase (GST) and acetylcholinesterase (AChE)-inhibiting activities were also assessed for these three ITCs in S. invicta workers. All three ITCs inhibited both EST and GST activities, but not AChE. The IC50 values of AITC, 2PITC and 3MPITC for GST were 83.04, 15.23 and 16.39 mg/ml, respectively. These results suggested that naturally occurring ITCs might be potentially useful for developing fire ants control products.