Browsing by Author "Koukkari, Willard L."

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    Controlling Leafy Spurge and Canada Thistle by Competitive Species
    (1994-06) Biesboer, David D.; Darveaux, Bettina; Koukkari, Willard L.
    A study was performed to assess the use of perennial native grasses in the control of leafy spurge and Canada thistle and also to evaluate the effects of herbicides applied during the fall to leafy spurge crown buds. As part of an integrated vegetation management program, grass treatments containing the native prairie grass little bluestem established well and were effective at reducing the cover of leafy spurge. Paramount to the success of using native grass species is getting adequate grass establishment which necessitates the careful selection of grass species adapted to the specific site conditions. A fall application of the herbicide picloram at 0.5 and 1.0 lb ai/acre was very effective at controlling leafy spurge and may be mediated via the direct absorption of picloram by the elongated crown buds at this time. The report contains an extensive literature review of the biology and weed control efforts of both leafy spurge and Canada thistle.
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    Time Responses and Susceptibility of Roadside Plants to Growth Regulation
    (Minnesota Agricultural Experiment Station, 1980) Koukkari, Willard L.
    Time responses, particularly daily oscillations, of seven species of plants were studied. Five of the species were weeds: Ambrosia artemisiifolia L., common ragweed; Ambrosia trifida L., giant ragweed; Cirsium arvense (L.) Scop., Canada thistle; Euphorbia esula L., leafy spurge; and Taraxacum officinale Weber, common dandelion. Two were desirable as roadside ground cover: Medicago sativa L., alfalfa, and Trifolium pretense L., red clover. Methods were developed for germinating weed seeds, a process which is often difficult to accomplish in a laboratory. A chlorophyll assay that was selected and modified for the study should be valuable in monitoring the status of injury to a variety of roadside plants. Variations in plant populations and the lack of good statistical evidence were important factors in not being able to designate any one time of day to be consistently better for controlling weeds by 2, 4-dichlorophenoxyacetic acid (2, 4-D) under controlled environmental conditions. It is possible that changes which take place throughout the day in leaf orientation could be an important factor when considering procedures for controlling roadside weeds, such as sicklepod in southern states or velvetleaf in Minnesota.