Can we use semiochemicals to control Aphis craccivoraKoch?

Amaranthus hybridus L. (Amaranthaceae) is among the most important vegetable crop in several sub-Saharan countries. Aphis craccivora Koch (Homoptera: Aphididae) is an aphid species that cause significant losses in absence of chemical control. In this laboratory research, we evaluate the efficiency of informative substances (E-b-farnesene, methyl salicylate, essential oil of Ocimum gratissimum L. and Ocimum basilicum L.) to repel aphids from their host plant. Our assays were carried out in plastic trays containing twenty-five amaranth plants. In each tray, twenty apterous A. craccivora adults were placed on the central plant (release plant) associated with a semiochemical releaser containing 100 µl of the substance to be tested diluted in paraffin oil. The number of aphids was then counted on each plant surrounding plants every three-days for twelve days.
We observed a significant repulsive effect of O. gratissimum and O. basilicum essential oils, that considerably reduced the aphid population on the treated plant, compared to control. However, no repulsive effect of E-b-farnesene and methyl salicylate on aphids was observed. Bioactivities of these substances and their using as alternative aphicidal in integrated pest management are discussed