Efficacy of tithonia diversifolia extract as a potential bio-organic repellent and biopesticide against termites (Macrotermes subhyalinus)

Abstract

Termites (Macrotermes subhyalinus) pose a significant threat to agricultural tree farming in Uganda and globally. There is a need to identify an affordable and environmentally friendly approach that provides effective and sustainable pest control measures to protect tree seedlings from damage. T. diversifolia is has been reported as a practical solution in repelling termites in Northern Ugandan traditional farming. This study therefore assessed the efficacy of T. diversifolia dichloromethane extract on termite repulsion and mortality taking into consideration time of exposure. Repellency and mortality response were assessed using the randomized controlled area preference method. Ultra high-performance liquid chromatography triple quadrupole mass spectrometry (UHPLC-MS/MS) and UV-Vis spectrophotometry were used to profile and polyphenols of Tithonia extract. The mean percentage repellency over 48-hour exposure time was 11.33, 50.67, 78.67, 35.33, 36.00, and, 16.67 for 0% (Negative control), 25%, 75% and 100% and Nimbecidine (Positive control) respectively. These results indicate that an increase in extract concentration was proportional to repellency activity beyond which it was insignificant. T. diversifolia extract 50% w/v concentration showed the highest repellency over the first 3 hours of exposure. Extract concentration of 50% had the lowest average index of repellency (IR) value of 0.233±0.12 describing it as the strongest repellent proportion. There was an increase in mortality percentage of termites with increase in concentration over an increased exposure time. The 100% w/v extract had the highest mortality effect of 88.33% after 36-hour exposure time, while 50% dominated the effect registering 96.67% mortality. The 48-hour median lethal concentration (LC₅₀) was determined to be 51.39% w/v, indicating the concentration at which 50% mortality was observed in the test population. Total polyphenol content (TPC) and total flavonoids content (TFC) were 926.85±49.73 (0.93%w/w) mgGAE/100g, DW and 228.16±11.16 (0.23%w/w) mgQE/100g, DW respectively. Chlorogenic acid concentration was 626.25±13.99 µg/100g, DW. The IR of 0.23 and percentage repellency (PR) of 78.67% for 50%w/v extract indicate that T. diversifolia extract is a repellent rather than an attractant or neutral plant to termites. Furthermore, T. diversifolia was found to have some degree of targeted mortality that is directly proportional to concentration, with LC50 of 51.39%. This study indicates that T. diversifolia botanical extract demonstrates potential for termite management and control due to its repellent and mortality properties.

Keyword: Tithonia diversifolia