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Geyer Larkspur Phenology and Response to 2,4-D

Published online by Cambridge University Press:  12 June 2017

D. N. Hyder  and
L. D. Sabatka
D. N. Hyder
Affiliation:
Plant Sci. Res. Div., Agr. Res. Ser., U. S. Dep. of Agr.
L. D. Sabatka
Affiliation:
Colorado State Univ., Fort Collins, Colorado 80521
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Abstract

Mortality rates of Geyer larkspur (Delphinium geyeri Greene), a poisonous plant, were determined after spraying with (2,4-dichlorophenoxy)acetic acid at various stages of plant development in 1967 to 1969. Sprays of 2,4-D at 2.2 kg/ha were more effective at early than at late stages of development, but seldom exceeded 40% mortality. Uneven-aged stands and early drying (dormancy) of small non-flowering plants often prevented the exposure of all plants to a single application of spray; treated plants contorted but continued growth for 5 to 8 weeks after spraying; residual seed provided a source of new plants; and previously dormant rootstock buds gave rise to new shoot and root growth the year after spraying. These characteristics and escape mechanisms direct attention to possibilities of improving effectiveness by spraying two or three times in a single season.

Type
Research Article
Information
Weed Science , Volume 20 , Issue 1 , January 1972 , pp. 31 - 33
Copyright
Copyright © Weed Science Society of America 

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References

Literature Cited

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