POTENTIAL OF WHEAT CULTIVAR MIXTURES FOR GREENBUG (HOMOPTERA, APHIDIDAE) MANAGEMENT

Greenbug, Schizaphis graminum (Rondani), biotypes C and E were used to test mixtures of susceptible and resistant cultivars of wheat, Triticum aestivum L. Three tests were completed in this study. In the first test, two wheat cultivars were used-one susceptible and one resistant to biotype C greenbugs. The cultivars were mixed in five ratios ranging from 100 to 0% resistance and infested with greenbugs at three different levels. The second test was similar, except biotype E greenbugs and the appropriate resistant cultivar were used. Based on damage ratings, plant height measurements, and population levels attained after 2 wk, a cultivar ratio of 75% resistant: 25% susceptible plants can be used to manage biotype C and E greenbugs. In the third test, mixtures of biotypes C and E were used to infest mixtures of three wheat cultivars. One cultivar was resistant to biotype C, one was resistant to biotypes C and E, and the third cultivar was susceptible to both. Only one infestation level was used in this part of the study. Plant damage ratings, plant height measurements, and population levels were analyzed 2 wk after infestation. The results from the test with mixtures of biotypes C and E indicated that there was no advantage to using mixtures of three rather than two cultivars.