Khwatenge Isaac1* and Wilber Lwande2 1International Centre of Insect Physiology and Ecology (I.C.I.P.E)2University of Nairobi, Chemistry Department
| A Zea may is a stable crop in most parts of the world and Africa in particular. But stem borer pest destroy the crop and reduce the yield considerably by 13% of the potential value of crops to insect pests. It is thought that volatiles emanating from Zea mays play part in orienting the Insect pest towards the host plant. It is for this reason that the current research was set out to extract, identify, determine concentration levels and carry out bioassay on airborne volatiles emanating from the seedlings using GC-MS and GCEAD. Twenty five compounds identified from zea mays were ; Toluene (4.4%), Octanal (0.7%), Nonanal (2.9%), (E)- hex – 3 – enylacetate (3.7%), cis – dihydrocarveol (1.4%), 4,8 – dimethyl – 1,3,7 – nonatriene (21.4%), decanal (3.2%), 3 – eicosine (1.0%), copaene (41.8%), zingiberene (6.8%), α-bergamotene (3.7%), 8 – cedrene (trace), cis – caryophyllene (26.4%), β – caryophyllene (4.1%), (α + β) – humulene (2.5%), α – amorphene (0.8%), patchoulene (2.3%), 1 – cholorohexadecane (5.1%), lidol (2.7%), cadinene (6.9%), γ – cadinene (0.9%), α – farnesene (trace), β – springene (8.8%), caryophyllene oxide (1.0%), 1 – pentacontanal (2.1%). Active compounds for zea mays sample were determined using Gas chromatography coupled with Electro – antennal detector (GC – EAD) technique. Zea mays sample showed five active peaks corresponding to 4, 8 – dimethyl – 1, 3, 7 – nonatriene (21.4%), cis – caryophyllene (26.4%), 1 – chlorohexadecane (5.1%), α – farnesene (trace), β – springene (8.8%). Also among the other identified compounds viz, 4, 8 – dimethyl – 1, 3, 7 – nonatriene, caryophyllene and α – farnesene, have been found by other researchers to be attractive to insect pests though in this study they did not indicate such. Since the five volatiles evoked a response on a GC – EAD detector mounted with an antenna from Chilo partellus pest, it is evident that the five compounds were bioactive. Thus an odour emanating from zea mays plays a role in the orientation of Chilo partellus insect pests towards the maize crop and in ultimate recognition of the host plant for feeding and ovi position that in turn lead to crop damage |
