Assessment of the insecticidal potency of neem (Azadirachta Indica) seed kernel methanolic and aqueous extracts on the malaria vector Anopheles gambiae

The potency of aqueous and methanolic extracts of neem (Azadirachta indica A. Juss) seed kernel, in inhibiting and disrupting development of Anopheles mosquito was assessed in the laboratory. Different concentrations of aqueous and methanolic extracts were tested on eggs, larvae and pupae. Both extracts were found to cause mortality on the specimens used and the level of mortality was concentration dependent. Mortality increased as the concentration increased. Methanolic extract of the neem seed kernel caused significantly higher (P = 0.05) mortality than aqueous extract. Few adults emerged among those treated with lowest concentration of 1 %( wt./vol.) aqueous extract, whereas no larvae or pupae survived to next stage in methanolic extract of the same concentrations. At highest concentration of 5 % (wt/vol), both extracts caused 100% mortality of larvae although the methanolic extract gave a quicker kill (12 hours) than the aqueous extract (24 hours). No egg hatched in all concentrations of both extracts

Management of african rice gall midge Orseolia oryzivora Harris and Gagn&#233 with reference to time planting and natural enemies in southeastern Nigeria

Field experiments were conducted at Abakaliki to evaluate the effect of time of planting (July 31, August 14 and August 28) and natural enemies in the control of African rice gall midge during the 2002 and 2003 cropping seasons. The experiment was laid out in randomized complete block design with three replications. The incidences of African rice gall midge were highest on rice planted on July 31 for both seasons and declined with the subsequent time of planting. The level of infestation by African rice gall midge was observed to depend on prevailing climatic factors. On the other hand, natural enemy found parasitizing African rice gall midge was Platygaster diplosisae Risbec. Parasitism by Platygaster diplosisae as a control measure of African rice gall midge was more severe as time of planting were delayed with 66.98 and 59.47% parasitism recorded on rice planted on August 28 for both years. This relationship was the significant negative correlation (r = -82 and -72 for 2002 and 2003 respectively) established between damage incidence and parasitism. Grain yield was least on rice planted on July 31 in all the experimental years. The highest grain yields were recorded on rice planted on August 14 for the two seasons. br> Journal of Agriculture, Forestry and the Social Sciences Vol. 3 (2) 2005: pp.106-11