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BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

The intensive use of synthetic pesticides in cowpea storage has led to the development of resistance by Callosobruchus maculatus and subsequent degradation of grain quality. In an attempt to circumvent these constraints, the susceptibility of C. maculatus to 2,2-dichlorovinyldimethyl phosphate (DDVP) and Lippia adoensis essential oil (EO) was investigated and variations in the proportions of nutritional values of treated grains 150 days after storage were assessed. The survival rate was recorded after five generations. The resistance index and biochemical parameters of grains were determined. The results from this study revealed that the survival rate and resistance index significantly increased proportionally with damage in DDVP treatments (r = 0.889; p = 0.018) while in EO treatments, those values remained low without significant variations (p = 0.0764) throughout the generations. DDVP stored grains yielded higher crude protein values, but lower carbohydrates, tannins, phenolics and minerals compared to EO. Eighteen amino acids were detected in EO treated grains and 14 in DDVP which was devoid of albumin and prolamin. Lippia adoensis EO could therefore represent a safe alternative bio-pesticide to cope with insect resistance and enhance the nutritional qualities of stored cowpea seeds.

Four oils from Piper nigrum, Litsea cubeba, Zanthoxylum bungeanum and Curcuma longa were obtained by ethanol extraction. The repellency of these oils and two major compounds (linalool and piperine) was evaluated against female adult and third-instar nymphs of the rice pest, Nephotettix cincticeps, under laboratory and glasshouse conditions. Paired-choice and no-choice assays were used for each treatment, with essential oils evaluated after 24 and 48 hr of exposure and chemical compounds evaluated after 12 and 24 hr of exposure. The potential effects of essential oils on activities of glutathione S tranferase (GST), carboxyl esterase (CarE) and acetyl cholinesterase (AchE) were also evaluated after 48 hr of exposure to leafhoppers. The constituents of the essential oils were determined using GC-MS. The results showed that the major components in the oils were piperine (34.75%) for P. nigrum, 9,12-octadecadienoic acid (Z,Z) (18.74%) for L. cubeba, ethanone, 1-(2-hydroxy-4,6-dimethoxyphenyl) (18.51%) for Z. bungeanum and turmerone (15.89%) for C. longa. In all cases, the essential oils repelled female adults and third-instar nymphs of N. cincticeps. The repellency of the tested oils and chemicals compounds in the paired-choice assay was higher than in the no-choice assay. In all experimental conditions, P. nigrum and C. longa oils were the most and the least potent, respectively. Linalool was the best repellent among the single-tested compounds under laboratory conditions. In the glasshouse study, the highest repellency was observed in the mixture of linalool and piperine. GST and CarE activities of leafhoppers were significantly enhanced by exposure to the four essentials oils; AchE activity increased significantly only in the P. nigrum and L. cubeba assays. Ourresults clearly indicate that the tested oils and chemical compounds are promising agents for developing plant-based pesticides to control N. cincticeps. K E Y W O R D Senzyme activity, essential oils, leafhopper, repellent