Environmental Entomology (1997) 26, 754-762

A.L. Roda, D.A. Landis and J.R. Miller (1997)
Contact-induced emigration of potato leafhopper (Homoptera: Cicadellidae) from alfalfa-forage grass mixtures
Environmental Entomology 26 (4), 754-762
Abstract: Studies were conducted. to evaluate the mechanisms leading to increased potato leafhopper, Empoasca fabae (Harris), emigration from alfalfa-forage grass mixtures. A laboratory behavioral bioassay was used to measure daily emigration rates of adult leafhoppers from alfalfa, Medicago sativa L.; smooth bromegrass, Bromus inermis Leyss.; orchardgrass, Dactylis glomerata L.; and timothy, Phleurn pratense L., alone and in 1:1 mixtures of each grass with alfalfa. Emigration was ~9-fold greater from pure bromegrass and orchardgrass treatments versus alfalfa alone, and ~5-fold greater than from mixtures of alfalfa and each grass species. In a 2nd, experiment, alfalfa and forage grasses were separated by a barrier permeable to plant volatiles. Only 31% of the potato leafboppers placed on alfalfa adjacent to either alfalfa or grass emigrated. However, when introduced to the side containing a forage grass, <85% of the leafhoppers emigrated, regardless of adjacent plant. Thus, stimuli obtained from physical contact with the grass versus grass volatiles alone were required to elicit emigration. Observations of potato leafhoppers on single plants of smooth bromegrass, orchard-grass, and alfalfa revealed that individuals fed on all 3 species; however, the frequency and duration of probing differed as did mean residency time (10.7 h alfalfa, 7.5 h bromegrass, 5.9 h orchardgrass). These experiments suggested that physical contact is necessary to elicit emigration from grasses. By increasing emigration, alfalfa-forage grass mixtures. may reduce potato leafhopper damage to alfalfa. Additionally, intercropping with forage grasses may lower the number of feeding bouts on alfalfa and reduce subsequent hopperburn.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): James R. Miller

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Empoasca fabae	Alfalfa/lucerne (Medicago sativa)