Responses of Glossina pallidipes and Glossina morsitans morsitans tsetse flies to analogues of δ-octalactone and selected blends

Abstract

Previous studies have shown that δ-octalactone is an important component of the tsetse-refractory waterbuck (Kobus defassa) repellent odour blend. In the present study, structure-activity comparison was undertaken to determine the effects of the length of the side chain and ring size of the lactone on adult Glossina pallidipes and Glossina morsitans morsitans. The responses of the flies to each compound were studied in a two-choice wind tunnel. Increasing the chain length from C3 (δ-octalactone) to C4 (δ-nonalactone) enhanced repellency to both species (G. pallidipes from 60.0 to 72.0 %, and G. m. morsitans from 61.3 to 72.6 %), while increasing the ring size from six (δ-octalactone) to seven members (ε-nonalactone) changed the activity from repellency to attraction that was comparable to that of the phenolic blend associated with fermented cow urine (p > 0.05). Blending δ-nonalactone with 4-methylguaiacol (known tsetse repellent) significantly (p < 0.05) raised repellency to 86.7 and 91.7 % against G. pallidipes and G. m. morsitans respectively. Follow-up Latin Square Designed field studies (Shimba hills in coastal areas in Kenya) with G. pallidipes populations confirmed the higher repellence of δ-nonalactone (with/without 4-methylguaiacol) compared to δ-octalactone (also, with/without 4-methylguaiacol). The results show that subtle structural changes of olfactory signals can significantly change their interactions with olfactory receptor neurons, and either shift their potency, or change their activity from repellence to attraction. Our results also lay down useful groundwork in the development of more effective control of tsetse by ‘push’, ‘pull’ and ‘push-pull’ tsetse control tactics.

Urina de vaca como biopesticida e biorrepelente: revisão sistemática da literatura

“…A base de dados Pubmed apresentou 13 resultados para os termos cattle urine AND insects, 6 para cow urine AND biopesticide, 5 para cow urine AND repellent e zero para os demais conjuntos de termos empregados na busca. Relativo ao período de publicação dos estudos, obteve-se um artigo publicado no ano de 2011 (Meena et al, 2011); um em 2013 (Rakesh et al,2013); um em 2014 (Kambar et al, 2014); três para o ano de 2016 (Gahukar, 2016;Isberg et al, 2016;Wachira et al, 2016); um em 2018 (Bijewar e Chouragade, 2018) e dois estudos em 2019 (Musonye et al, 2019; Thakur e Sood, 2019). A figura um apresenta o esquema e ordenação das etapas seguidas para a seleção das pesquisas nas bases de dados a partir dos descritores utilizados.…”

“…Ano de publicação, local de origem da pesquisa, coleta/preparo da amostra e finalidade de uso da urina de vaca nas publicações. (Meena et al, 2011;Rakesh et al,2013;Kambar et al, 2014;Gahukar, 2016; Bijewar e Chouragade, 2018; Thakur e Sood, 2019); dois (22,2 %) no país africano Quênia (Wachira et al, 2016;Musonye et al, 2019) e um (11,1 %) artigo na Suécia (Isberg et al, 2016).…”

Responses of Glossina fuscipes fuscipes to visually attractive stationary devices baited with 4-methylguaiacol and certain repellent compounds in waterbuck odour

“…Most studies that compare trap catches of tsetse flies exposed to several treatments of odorants use Latin square design experiments [10, 11, 13, 15]. This is because it can control for variation of fly catches due to the trap site and day at study design stage [41].…”

“…Variations in lactic acid concentrations in human odour were identified to be responsible for this repellency [12]. Since then, a number of synthetic and naturally occurring repellent compounds have been identified [9–11,13–15]. Among these are; acetophenone and 4-methylguaiacol which have been shown to reduce catches of G .…”

“…pallidipes by 69% and 80% respectively [11,13], and δ-nonalactone which reduce G . pallidipes catches by 76% when used in attractant odour baited traps [15].…”