Distribution, Competition, and Phenology of Hemp Dogbane (Apocynum cannabinum) in Nebraska

Abstract

All land uses in eastern and southeastern Nebraska were infested to some extent with hemp dogbane (Apocynum cannabinumL.). The highest infestations were observed in oats (Avena sativaL.) and soybeans [Glycine max(L.) Merr.] and the lowest infestations were in alfalfa (Medicago sativaL.), pastures, and winter wheat (Triticum aestivumL.). Yield reductions from hemp dogbane infestations ranged from 0 to 10% in corn (Zea maysL.), 28 to 41% in soybeans, and 37 to 45% in sorghum [Sorghum bicolor(L.) Moench]. Emergence of hemp dogbane from crown roots occurred when the soil temperature was 17 to 19 C, during April in 1977 and 1978. Plants attained the bud stage within 4 to 7 weeks after emergence. Early flower, full bloom, and pod initiation occurred subsequently at about 1 week intervals. Seeds produced were first viable 10 weeks after full bloom. Root activity or regenerative capacity as measured by length and number of new shoots and roots produced at monthly intervals in the germinator showed a cyclic pattern. The highest activity occurred in the spring and late fall and lowest activity in summer and early fall. Protein levels in the roots ranged from 7 to 9% in the fall and spring to 4 to 5% during the summer. Percentage total nonstructural carbohydrates (TNC) ranged from 20 to 31% in lateral roots and 32 to 53% in crown roots, but there was not a consistent cyclic pattern of percentage TNC during the growing season.

Translocation of Nicosulfuron and Dicamba in Hemp Dogbane (Apocynum cannabinum)1

“…Hemp dogbane is a deep-rooted perennial broadleaf weed that reproduces by seeds, basal crown buds, and lateral root buds (Becker 1981;Orfanedes and Wax 1991). Lateral roots spread from just below the crown of hemp dogbane and buds on lateral roots develop into new plants the following spring to form dense, circular patches that can reduce crop yields (Schultz and Burnside 1979a;Triplett 1985). Crown buds are the primary source of vegetative regrowth following disturbance of the shoots, and like lateral roots, crown buds can overwinter (Becker and Fawcett 1998;Robison and Jeffery 1972).…”

Hemp Dogbane (Apocynum cannabinum) and Wild Blackberry (Rubus allegheniensis) Control in No-tillage Corn (Zea mays)

“…Hemp dogbane spreads radi ally by lateral roots, producing a dense patch which can interfere with harvesting. Schultz and Bumside (11) found that yields of irrigated com in fields infested with hemp dogbane had an average yield loss of 5 to 10% over 3 yr. Coffman and Frank (2) observed that wild blackberry spread in a com field following five con secutive years of reduced tillage. No information is available on the effects of wild blackberry on com yields.…”

Differential Response of Hemp Dogbane (Apocynum cannabinum) to Clopyralid, Dowco 433, and 2,4-D

“…The species can be found throughout much of the United States and southern Canada (5, 6). Hemp dogbane reproduces from seed, basal crown buds, and budding roots (6,24,26). Roots are usually found 15 cm below the soil surface or deeper and grow in a lateral direction away from the parent plant.…”

“…In cultivated fields, hemp dogbane is usually found growing in small, isolated patches (24,26). However, vegetative reproduction via budding roots allows infest ations to intensify and spread over time (1,24,26). Control of hemp dogbane is difficult due to its persist ent and extensive system of roots with adventitious buds.…”