Effect of the postfeeding interval on olfactory responses of thrips to herbivore-induced cotton plants

We investigated the responses of 3 thrips species, Frankliniella schultzei Trybom, F. occidentalis Pergrande, and Thrips tabaci Lindeman (Thysanoptera: Thripidae) to herbivore-damaged and undamaged cotton seedlings (Gossypium hirsutum L. [Malvales: Malvaceae]) at a range of time intervals following damage by adult Tetranychus urticae (Koch), adult T. ludeni (Zacher) (Acari: Tetranychidae) or Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae in olfactometer assays. The intensity/frequency of the response of thrips to herbivore-induced plants decreased with time and ultimately disappeared in all cases; however, the rate at which the response declined was related to the herbivore species that inflicted the damage. All 3 species of thrips were attracted to plants damaged by T. urticae for longer than they were to plants damaged by T. ludeni. The duration for which damaged plants remained attractive was also affected by the degree of damage inflicted on cotton seedlings. For example, F. schultzei was attracted to plants damaged by a higher density of two-spotted spider mites (100/plant) for much longer than to plants damaged by a lower density of these mites (50/plant). The results reinforce previous studies that demonstrate that arrangement of variables influences the responses of thrips to their herbivore-induced cotton host plants. Results also show that these responses are variable in time following herbivore damage to cotton plants, which further demonstrates how difficult it is to generalize about the functional significance of these interactions.