Acaricidal activities of Cymbopogon citratus (DC) Stapf against Blomia tropicalis van Bronswijk, Cock & Oshima (Astigmata: Echimyopodidae)

Abstract

ABSTRACT Blomia tropicalis (Astigmata: Echimyopodidae) has been classified as the most crucial mite pest of stored agricultural commodities that causes human allergies. The present work aims to assess the susceptibility of B. tropicalis to Cymbopogon citratus extract (CCE). A total of four strains were tested, representing the top agricultural provinces in the Philippines. The result revealed that the most susceptible strain of B. tropicalis was MsORMR10 with LC50 and LC99 of 0.47 and 1.02 g/L of CCE. However, the CebVR6 got the highest response to CCE, with 0.99 g/L for the LC50 and 1.73 g/L for the LC99, respectively. The strain with the highest response to CCE was subjected to progeny assay. The minimum effective concentration that gives complete mortality of the most resistant strain (CebVR6) of B. tropicalis progeny was 2.00 g/L. Twenty-four chemical compounds were identified in CCE. The seven major compounds were the following: 6a,14a-Methanopicene, perhydro- 1,2,4a,6b,9,9,12a-heptamethyl-10-hydroxy (29.23%), g-Sitosterol (14.93%), Oleyl alcohol, methyl ether (11.59%), 6-Methylheptan-3-ol (9.20%), Squalene (5.44%), Menthol (5.23%), and Citral (3.80%). Lastly, the CCE as an acaricide was found to be superior to synthetic acaricides on the market in terms of efficacy and volume concentration. Consequently, it has the potential to replace synthetic commercial acaricide.