Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Population dynamics and spatial distribution of Lysiphlebus testaceipes (Cresson)(Hymenoptera: Braconidae) and its host, the greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae): Studies for the development of an augmentation program
Abstract
The dynamics, spatial distribution and labeling of the parasitoid, Lysiphlebus testaceipes, and its host, the greenbug, Schizaphis graminum, were studied on sorghum. Parasitoids were released at several rates in caged sorghum previously infested with greenbugs during 1993 and 1994. Sampling of greenbugs and mummies was conducted weekly. During a 3-year period, both greenbugs and parasitoid mummies were sampled in a biotype E-greenbug-resistant-hybrid grain sorghum field intercropped with susceptible-hybrid strips. Labeling both insects using rubidium chloride as physiological a marker was performed under laboratory and field conditions by spraying plants. The parasitoid was able to keep greenbugs under the economic threshold when release rates averaged 0.33-0.5 parasitoids per plant infested initially with 20 greenbugs. These rates also optimized the production of mummies. Leaves of the mid-third of the plant are the best sampling unit for caged sorghum studies because they produced the highest correlation between the number of insects on them and number of insects on the plant. Although, greenbug populations start decreasing when 20% parasitism is reached, the population growth slows down when parasitism is in the range of 10-20%. In 1994, yield was significantly increased when 0.5 parasitoids per plant were released, compared with no parasitoids released. Greenbugs and mummies are more likely to be found on lower leaves of sorghum plant in the field regardless of the hybrid. These leaves also produce the highest correlation between number of insects present and total on the plant. In both caged and uncaged sorghum, these insects are primarily on the lower surface of leaves. Rubidium content was significantly greater on both greenbugs and parasitoids after spraying plants with doses greater than 2,500 ppm of RbCl in aqueous solution. Rubidium could be detected in individual insects. Labeled parasitoids were released and recaptured using sticky traps and dispersed at least 60 m in the first day.
Subject Area
Entomology|Ecology|Agronomy
Recommended Citation
Fernandes, Odair Aparecido, "Population dynamics and spatial distribution of Lysiphlebus testaceipes (Cresson)(Hymenoptera: Braconidae) and its host, the greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae): Studies for the development of an augmentation program" (1995). ETD collection for University of Nebraska-Lincoln. AAI9538630.
https://digitalcommons.unl.edu/dissertations/AAI9538630