24. Evaluation of Season-Long Mechanical and Low Herbicide Input Treatments for Leafy Spurge Suppression.  C.M. Scholes and S.A. Clay, Plant Science Dept., South Dakota State University.

Conventional management of leafy spurge may be inappropriate in certain situations. Other control options are needed for spurge patches in trees or along waterways. Four alternative control strategies were studied for leafy spurge suppression effectiveness. The methods tested were continuous black plastic smother, mowing at 2 and 4 week intervals, and 0.11 kg/ha-1 of 2,4-D (0.1 X rate) applied at 2 week intervals 10 times during the season. These control methods were compared to control (no treatment) and a 1 X rate (1.12 kg/ ha-1) of 2,4-D. In 1992 treatments were applied to 12m x 12m plots. In 1993 plots were split so that half were treated and half were untreated. Plots were sampled at least once every 4 weeks and treatments were applied after each sampling date, as appropriate. Sampling occurred from late May to early October and included determination of leafy spurge stem density, leafy spurge biomass, and associated vegetation biomass.

Table 1.  Leafy spurge density and biomass, and associated plant biomass on three sampling dates in 1992.
TreatmentEPHES Density
(stems m-2)
EPHES Biomass
(g m-2)
Associated Plant Biomass
(g m-2)**
2,4-D 1X232223150101314156104192
Mow 2wk315225621041913663634
Mow 4wk2413417396315433452
2,4-D 2wk14071437825667238206
Isd (0.05)ns15399ns3842ns5847

*Sampling prior to treatment
**predominantly Bromus inermis and Poa pratensis

In 1992, all treatments reduced leafy spurge density and biomass (Table 1). Smother and mowing treatments decreased associated plant biomass while the 2,4-D 2-wk treatment had increased associated plant biomass production. No treatment had an affect on stem density that carried over into 1993. However, all treatments had less leafy spurge biomass that the control when evaluated in May 1993. All treatments prevented seed production the year of treatment. The best treatment was 2,4-D 2-wk because of good leafy spurge suppression and grass production.