Insecticidal Effects of Neem (Azadirachta Indica A. Juss) Oils Obtained from Neem Berries Stored at Different Periods

Among the studied botanicals worldwide neem tree is proved to be the richest in active compounds and one of potent sources of
natural biocides. Crude extracts of neem seeds showed significant results as insecticides in Sudan where optimum doses are recommended for several vegetable pests. Since neem products of different ages are used for this purpose, laboratory experiments were conducted to compare the insecticidal effects of crude oils extracted from seeds of neem berries stored at different durations under normal room conditions. The 3rd instar larvae of Trogoderma granarium were used as test insects. Comparing all treatments, the highest insect mortalities were attained by the highest concentration (5%) used. The general performance of the different products revealed insignificant slight decreases in oil activities as the storage period of neem fruits increased from one to seven years, afterward a sudden significant drop in potency was occurred for the eight-year old product. Moreover, the same trends were attained regarding
sorghum grains damaged by the larvae, as the lowest losses were shown by the highest oil concentration of the products stored between one to seven years. Accordingly, it was advised that oils of neem products stored between one to seven years can be equally used as effective natural insecticides, but newest products of one to four years old are preferable. However, the additive materials incorporated in neem oil, which seemed to improve its potency, may need additional investigations.