ACARICIDAL EFFECTS OF CARDIAC GLYCOSIDES, AZADIRACHTIN AND NEEM OIL AGAINST THE CAMEL TICK, HYALOMMA DROMEDARII (ACARI: IXODIDAE)

Abstract

The cardiac glycoside, digitoxin, from Digitalis purpurea L (Scrophulariaceae), a cardiac glycosidal (cardenolide) extract from Calotropis procera (Ait) R Br (Asclepiadaceae) azadirachtin and neem oil from Azadirachta indica A Juss (Meliaceae) were tested for their effects against larvae and adult stages of the camel tick, Hyalomma dromedarii Koch (Acari: Ixodidae). The contact LC50 values of the first three materials against adults were 4.08, 9.63 and > 40.7 µg cm-2, respectively, whereas the dipping LC50 values of the extract and azadirachtin against larvae were 6.16, > 20.3 µg cm-2, and 587.7 and > 2500 mg litre-2, respectively. Azadiracthin had no effects on egg production or feeding of adults up to 500 mg litre-1; however at 2500 mg litre-1, it caused significant reduction in feeding activity of larvae, prolonged the period for moulting to nymphal stage, and caused 60% reduction in moultability. Results of the two cardiac glycoside materials are comparable with those of several commercial acaricides. The risks and benefits associated with the use of cardiac glycosides are considered.