An in vitro ULV olfactory bioassay method for testing the repellent activity of essential oils against moths

A prototype olfactory device was developed and used for first time to study the bioactivity of Ultra Low Volumes (ULV) of three essential oilsagainst the moth pest Anarsia lineatella (Lepidoptera: Gelechiidae). Particle sizes calibration and standard ULV time-doses range tests were performed prior the olfactory bioassays. Three essential oils were tested Cymbopogon citratus (Lemon Grass), Gaultheria procumbens (Winter Grass) and Rosmarinus officinalis (Rosmarin) according to the proposed method. The most active oil was that of R. officinalis and moths expressed approximately 3–5 fold faster moving behavior (50% repellence response times to ULV, RT50: 20–30 min) compared to G. procumbens (RT50:74–79 min) and C. citratus (RT50:82–96 min). Apart from direct observed repellence, moths sprayed with ULV show clearly signs of knock down symptoms and high fatality in a period 15–60 min after their treatment especial in the case of R. officinalis. Longevity of female moths was significantly affected by the initial ULV application. Furthermore, choice test showed that essential oils significantly deterred oviposition in most cases. Considering the urgent need for alternative to conventional pesticides the current work may provide a framework of testing the bioactivity of bio rational compounds in the form of ULV and under Lab conditions.