Induced Walking Behavior of Rhopalosiphum Padi L. (Homoptera: Aphididae)

126 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2002.Movement of apterous adults and fourth instar nymphs was monitored following different perturbations and combination of perturbations. Apterous aphids, caged overnight on oat plants in a 25-plant infestation focus in the center of each 900-plant plot, were subjected to a given perturbation or combination of perturbations after the cages were removed and then allowed to move freely within the plot for 48 hrs. The presence of aphids outside the infestation focus provided direct evidence of aphid movement. All perturbations caused a significantly high number of aphids to move outside of the infestation focus. The mean distances dispersed, however, were statistically similar for all perturbations with the exception of drought. The highest levels of aphid movement were observed when crowding conditions were imposed, but the mean distance that crowded aphids moved was significantly shorter than the distance traveled by aphids under controlled conditions. Aphids were also subjected to multiple perturbations; results form these studies suggest that in any pair of perturbations, the dominant factor dictates the degree of aphid movement. Non-dominant perturbations play very minor roles in the total number of aphids dispersed when simultaneously under a dominant perturbation, but the occurrence of a secondary perturbation can increase the mean distance traversed and change the pattern of aphid dispersal. Results also suggest that aphids might be able to sense the presence of nearby conspecifics. If crowding conditions are detected, aphids tend to move toward the outside of the crowded center of the arena. However, once a suitable host is located, they tend to colonize it and not to travel farther in search of other plants to colonize.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD