Author
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SHISHKOFF, N - 1920-05-00 |
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Bruckart, William |
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Submitted to: Biological Control
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/10/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Purple and yellow starthistles are important rangeland weeds. These plants are from dry climates and grow very well in California. A rust disease from Turkey was studied for control of these plants in California. The rust only damaged yellow starthistle and not purple starthistle in earlier studies, but the plants in those studies were watered regularly and not allowed to wilt. Rusts are known to increase wilting of infected plants. The objective of this study was to determine if increased damage resulted when rust-infected starthistles were allowed to wilt daily. Allowing infected plants to wilt did not change the amount of damage to starthistles by the rust disease that was noted in the earlier studies. These results mean that normal watering in the greenhouse does not affect the relative amount of damage to the starthistle plants by the rust disease. Therefore, screening of starthistle rusts can be carried out under normal greenhouse watering regimes. These results also support earlier conclusions that the yellow starthistle rust disease may be good for biological control of yellow starthistle in California Technical Abstract: The effect of water stress and damage to Centaurea solstitialis L. (yellow starthistle) and C. calcitrapa L. (purple starthistle) caused by isolates of the rust Puccinia jaceae Otth was investigated under greenhouse conditions. Inoculated and uninoculated plants were placed under water stress, defined as reversible wilting; control plants received normal daily watering. Effects of drought stress and infection by P. jaceae were measured in terms of root biomass, lifespan of leaves with different disease levels, and the number of live and dead rosette leaves. Drought stress reduced root dry weights, leaf lifespan, and total number of rosette leaves of both yellow and purple starthistle. Infection by rust also reduced leaf lifespan and total rosette leaves of both species, but it only affected root biomass of yellow starthistle. The only significant interaction between drought stress and rust infection occurred with purple starthistle leaf lifespan, but this consisted of drought stressed leaves having short lifespans at all infection levels. Data from these experiments with drought-stressed plants did not alter previous conclusions that P. jaceae has promise as a biocontrol agent of yellow starthistle. The damage it caused was similar to that by P. chondrillina on skeletonweed in comparative studies |
