Mechanisms by Which Grass Reduces Potato Leafhopper, Empoasca Fabae (Harris) (Homoptera: Cicadellidae), Abundance in Alfalfa
Smith, Lane Martin, II
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/71108
Description
Title
Mechanisms by Which Grass Reduces Potato Leafhopper, Empoasca Fabae (Harris) (Homoptera: Cicadellidae), Abundance in Alfalfa
Author(s)
Smith, Lane Martin, II
Issue Date
1987
Department of Study
Entomology
Discipline
Entomology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Entomology
Abstract
The apparent repellency of grass was investigated in order to determine the means by which potato leafhoppers perceive the presence of grass, to determine the behavioral changes caused by grass which lower abundance in alfalfa, and to test the resource concentration hypothesis for the potato leafhopper in alfalfa.
In adult location and oviposition choice tests leafhoppers used primarily olfaction to perceive grass. In no-choice tests potato leafhoppers responded with greater movement rates, and both oocyte development and oviposition rates were decreased in the presence of grass in a dose-dependent manner. In addition, feeding of tethered leafhoppers on alfalfa was decreased in the presence of grass. Grass volatiles acted as locomotory stimulants, interrupting oviposition and feeding, and in addition having possible repellant effects.
In an alfalfa field at dusk, a higher percentage of the leafhoppers in grassy alfalfa were in flight and had fewer oocytes/female than in grass-free alfalfa, supporting conclusions from laboratory studies that presence of grass increases flight and decreases the number of oocytes/female.
Though potato leafhoppers are highly polyphagous, they are facultatively monophagous in an alfalfa field, therefore it is an ideal candidate for testing the resource concentration hypothesis. Two aspects of the resource concentration hypothesis were tested in field sampling: plant density (thinned and unthinned alfalfa) and plant diversity (weedy and weed-free). Results showed that leafhoppers were more abundant on sparse alfalfa (leafhoppers/kg or leafhoppers/stem), while absolute density was higher on dense alfalfa (leafhoppers/m$\sp2$) for each life stage. As previous research indicates, leafhopper density decreased with increasing plant diversity (primarily increased grass density), and this response by the leafhoppers was found to be independent of the response to plant density. The response to host plant density ran counter to the resource concentration hypothesis. Laboratory supported these studies, showing that females and males preferred to settle in sparse alfalfa and oviposition was greater in sparse alfalfa compared with dense alfalfa.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
