Laboratory Evaluation of a Eucalyptus-based Repellent against Four Biting Arthropods

An evaluation of a new plant-based biting insect repellent (PMD) with the princial active ingredient p-menthane-3,8-diol is presented. Laboratory trials testing 50% active ingredient formulations of the repellent on a human forearm show good repellency against the malaria vector Anopheles gambiae Giles s.s. with an average ED90 value of 0.68 μL/cm2 and effective protection from biting for around 5 h. These results compare favourably with a 20% deet product, (ED90 value of 0.48 μL/cm2 with 5 h protection), and are far superior to the best known existing plant-based product, citronella (ED90 value of 1.37 μL/cm2 and 2 h protection). PMD was also found to give total protection against the biting midge, Culicoides variipennis Coquillett, for at least 6 h at 0.35 μL/cm2. When evaluated against the deer tick, Ixodes ricinis L., attachment and subsequent feeding of I. ricinis nymphs was significantly reduced on rabbit ears treated with 0.36 μL/cm2 of PMD. Against the stable fly, Stomoxys calcitrans L, an application of 0.5 mL PMD to a human forearm reduced biting to 6% of the control biting level. It is concluded that PMD is a broad spectrum repellent with considerable potential as means of personal protection against nuisance biting and insect-borne disease.