Background: Cimex lectularius Linnaeus and Cimex hemipterus L. (Bedbugs) are hematophagous ectoparasites which are a nuisance and public health menace. In recent past, bed bug infestation has been on the rise which is attributed to the emergence of resistance to commercial insecticides, particularly pyrethroids. Therefore, the aim of this investigation was to evaluate the insecticidal properties of aqueous extracts of different plants on bed bugs.
Methods: Aqueous extracts separately obtained from four different plant materials; ripe fruits of Capsicum annuum L. (hot pepper), fruit peelings of Citrus x sinensis L. (citrus: orange), leaves of Tagetes minuta L. (Mexican marigold) and bulbs of Allium sativum L. (garlic) were studied against bedbugs in a controlled laboratory setting and their effect based on chemotaxis and mortality observed. The extracts were further tested in a field trial in seven villages randomly selected from Idakho central ward, Ikolomani constituency, Kakamega County, Kenya. The villages were assigned arbitrary identity as V1, V2, V3, V4, V5, V6 and V7. Twenty households confirmed to be infested with the bedbugs were selected randomly from each sample village. Each village received specific treatment; V1, V2, V3, V4 and V5 were treated with 5ml of 10mg/ml of extracts from Capsicum annuum, fruit peelings of Citrus x sinensis, leaves of Tagetes minuta, bulbs of Allium sativum and a concoction of the four extracts at the ratio of 1:1:1:1 respectively. Village V6 was treated with commercial potent synthetic insecticide (Bedlum® 200SL, Jiansu Lanfeng biochemical, China with acetamiprid as active compound) as a positive control and village V7 was treated with distilled water as a negative control.
Results: The laboratory findings showed that the bed bugs had negative chemotaxis to T. minuta and A. sativum and also showed some direct mortality. Capsicum annuum and C. sinensis had a direct killing effect on the bedbugs. The combination of extracts from the four plants showed 100% mortality within the shortest time of 10 seconds as compared to individual plant extracts. The findings from field trials showed higher perception of bedbug management of 90% for a concoction of the four extract as compared to individual plant extracts: 55%, 70%, 40% and 45% for C. annuum C. sinensis T. minuta and A. sativum respectively. Both laboratory and field trial findings showed that a concoction of the four named plants is a potent insecticide and can be used in bedbug management. There is however need to carry out more research to ascertain other active compounds in the extracts and their mode of action.
Key words: Potent, Cimex lectularius, Cimex hemipterus, Capsicum annuum, Citrus x sinensis, Tagetes Minuta, Allium sativum Bedbug management, Concoction, mortality, Chemotaxis