Rapid Technique for Determining Greenbug (Homoptera: Aphididae) Biotypes B, C, E, and F

Publisher Website
Google Scholar
Abstract
A method for quickly determining greenbug, Schizaphis graminum (Rondani), biotypes B, C, E, and F was developed. ‘Largo’ resistance in ‘TAM 105’ × ‘Largo’ (5 × L), ‘Triumph 64’ (TR), ‘TAM 107’ (107), and ‘CI 9058’ was evaluated against biotype F so these host relationships could be compared to other biotypes. Mean damage ratings for 5 × L did not differ significantly from the susceptible checks, TR and 107. Therefore, only TR, 107, and 5 × L are needed to differentiate the biotypes. These cultivars were exposed for feeding exposure times of 1, 2, 4, and 6 h to determine the time required for each biotype to make lesions. Feeding damage appeared as brown lesions on the leaves of susceptible plants. Lesions did not form on cultivars resistant to each biotype. Counts of lesions per leaf were made 24, 48, 72, and 96 h after infestation. All of the lesions that were to appear did so by 72 h after infestation. Some of the susceptible plants developed lesions at the 1- and 2-h feeding exposure. All of the susceptible plants formed lesions at the 4- and 6-h feeding times. Mean lesion numbers of 5.0 and 5.2 for 4 and 6 h, respectively, were not significantly different. Our technique permits biotype determinations to be made within 2 wk after aphid collection. Details on the construction of a clip cage, which is an integral part of the methodology, are provided.