Control of Common Milkweed (Asclepias syriaca)

Abstract

Control of common milkweed (Asclepias syriacaL.) with postemergence herbicides was investigated in greenhouse and field experiments. In greenhouse experiments, amitrole (3-amino-s-triazole), dicamba (3,6-dichloro-o-anisic acid), glyphosate [N-(phosphonomethyl)glycine], and combinations of amitrole + dicamba, dicamba + 2,4-D [(2,4-dichlorophenoxy) acetic acid], glyphosate + 2,4-D, and glyphosate + dicamba reduced regrowth of 6-week-old common milkweed as compared with the untreated check. Postemergence herbicides commonly used in corn (Zea maysL.), sorghum [Sorghum bicolor(L.) Moench], and soybeans [Glycine max(L.) Merr.] had little effect on emerged common milkweed. Removal of common milkweed top-growth as early as 1 day after treatment did not effect subsequent growth reduction from glyphosate at 0.3 kg/ha or higher. In the field, satisfactory control (70% or better) of common milkweed was obtained with glyphosate at 2.2 kg/ha applied at the early or late bud growth stage. Plots plowed 1 day after application of glyphosate at 2.2 kg/ha still retained satisfactory control of common milkweed 1 yr after treatment. Herbicides applied with a herbicide glove or a roller applicator resulted in common milkweed control similar to that obtained from broadcast spray applications.

Glyphosate’s impact on vegetative growth in leafy spurge identifies molecular processes and hormone cross-talk associated with increased branching

“…No evidence of naturally occurring glyphosate-resistant plants was reported before the introduction of glyphosate-resistant transgenic crops, although several reports did indicate that biotypes of field bindweed ( Convolvulus arvensis ) and bermudagrass ( Cynodon dactylon ) were somewhat tolerant to glyphosate [ 3 , 4 ]. Laticiferous perennial weeds such as hemp dogbane ( Apocynum cannabinum ), common milkweed ( Asclepias syriaca ), and leafy spurge ( Euphorbia esula ) have also been reported as glyphosate tolerant weeds [ 5 – 7 ]. Regardless, control of invasive perennial weeds in non-cultivated ecosystems of North America, including leafy spurge, generally requires integrated pest management programs that incorporate the use of glyphosate [ 8 ].…”

Response of swallow-wort to herbicides

“…The glyphosate product label recommends application at the bud formation stage for herbaceous perennials. This is the timing recommendation for common milkweed (Asclepias syriaca L.) and is supported in work by Bhowmik (1982), June being better than August, and by Cramer and Burnside (1981), best at bud stage. Glyphosate foliar spray treatments were completed early in the flowering period, well before all buds had opened.…”

Invasive weed swallow‐wort (Cynanchum acutum L.) response to chemical and mechanical practices

“…Bromoxynil + MCPA, mecoprop‐p‐dicloprop‐p‐MCPA, and brush cutter were applied during C. acutum active growth stage. Glyphosate was used at the bud formation stage as recommended in case of herbaceous perennials such as common milkweed ( Asclepias syriaca L.) (Bhowmik, 1982; Cramer & Burnside, 1981). Triclopyr was applied at the early fruiting stage when photosynthates are translocated to below‐ground storage organs (Lawlor & Raynal, 2002).…”