Olfactory Behavior And Chemical Mechanism Of Phvllotreta Striolata In Response To Host Plants

Phyllotreta striolata (Fabricius)(Coleoptera:Chrysomelidae) is an economically important pest of Brassica crops worldwide. Recent studies showed that males of this pest could produced aggregation pheromone during feeding in plants. However, P. striolata showed also host selection preference to host plants. Thus the recognition mechanism of P. striolata responses to plant volatiles and aggregation pheromone is important for the control of this pest based on the usage of semiochemicals. In this study, a four-arm olfactometer was used to examine the olfactory behavior of P. striolata in response to different Brassica vegetable and/or vegetables which were infested already by P. striolata or feeding simultaneity. In addition, GC-MS was used for chemical analysis of plants and insect pests. Finally, Scanning electron microscopy was used for the observation of insect antennal sensilla.The main findings are summaried as follows:(1) Brassica chinensis was slightly more attractive than Brassica campestris to beetles, but much more attractive than Brassica oleracea L and Brassica oleracea L. var. botrytis L. However, the Brassica oleracea is equivalent to Brassica oleracea L. var. botrytis L.(2) Flea beetles were significantly attracted by B. campestris with feeding females, but showed significant aversion to B. campestris with feeding males whenever the plant seedlings were4or8leaves stage, or the experiments were performed on Spring or Autumn. Similar situation occurs for the plant B. chinensis.(3) Plant volatiles from four Brassica crops were compared. Hydrocarbons, ketones, alcohols, terpenoids, esters, and amides were identified. The difference of volatile chemicals and relative amount would be the main reason of the host selection preference.(4) Plant volatiles of B. campestris were significantly changed when the plants were fed or feeding by the beetle. Three new chemicals were released by male-plant complex, i.e. Cyclohexene, alpha-Caryophyllene and alpha-Farnesene. Whereas5new chemical were found from female-plant complex. They are Naphthalene, Cyclopertane, Cyclohexene, alpha-Caryophyllene and alpha-Farnesene.(5) Eleven types of sensilla were distinguished on the antennal of the beetle. However, the number and distribution of sensilla had no significantly difference between male and females.