Effect of vegetable oils as Phagostimulants in adults of Dichroplus vittigerum (Orthoptera: Acrididae)

Abstract

Several species of grasshoppers are attracted to vegetable oils. These oils have kairomonal properties mainly due to the presence of linolenic and linoleic fatty acids. This study aimed to determine whether the odors of canola, flax, and olive oils are attractive to Dichroplus vittigerum (Blanchard 1851) and if they induce preference and feeding. We conducted three bioassays to determine whether oil modifies attraction and feeding behavior of this grasshopper. We first determined the attraction of the oils using a wind tunnel, secondly evaluated phagostimulation produced by the oils, and finally performed preference tests comparing consumption of Taraxacum officinale (Weber ex F.H.Wigg. 1780, Asterales: Asteraceae) leaves treated with the oils versus control leaves. Even though all of the oils induced attraction, only flax oil acted as a phagostimulant. However, the oils did not determine the preference and did not increase feeding on leaves. We hypothesize that T. officinale leaves are inherently attractive and treatment with oils did not affect feeding on them. Our results provide a starting point to develop baits that can be used to attract and control these harmful insects, presenting flax oil as a potential bait for D. vittigerum since its odor was both attractive and led to increased feeding or phagostimulation. Future studies should test the effect of the oils on other plant species or at varying doses, under field conditions.