ISSUE 5 June 1, 2006
WEED CONTROL FROM SOIL APPLIED HERBICIDES
Extension specialists have been getting questions on activation of soil-applied herbicides, particulatly Spartan, Sencor, and Prowl H2O, under dry conditions.
If Spartan, Sencor, or Prowl H2O was applied as a preemergence application and it has not rained since application, how long before is it gone?
General principle for all soil-applied herbicides - if weeds emerge before the herbicides are activated then weed control will be reduced regardless if activating rains occur after weeds emerge.
Spartan and Sencor are not volatile and is not degraded by sunlight. Very little (if any) product will be lost on the soil surface if rainfall is delayed. The only movement would be if soil particle physically move from high wind velocities. Spartan will not be activated until a significant rainfall event has occurred and some weed escapes could occur. The question of how much rainfall is needed for activation is often asked. Typically, 0.5 inch of rainfall is needed to activate most herbicides. Once activated, Spartan and Sencor will provide residual control of susceptible weeds that have not yet emerged but not emerged weeds. Some control of small emerged pigweed has been observed with Spartan in the past but that should not be expected. Others say they have observed control of small kochia and russian thistle.
The new formulation for Prowl H20 is less volatile and less susceptible to UV sunlight degradation than the 3.3 EC Prowl formulation. But the general principle applies here again. If weeds emerge prior to the activation, then weed control will be reduced. Prowl does not control any weeds once emerged but can control un-emerged weeds once activated.
2006 HERBICIDE UPDATE - PART 1
(By Herbicide Company in Alphabetical Order):
Many active ingredients (ai) off now off patent resulting in numerous brand names for each ai. For partial list of many brand names associated with each a.i. see the mode of action section of the weed guide, pages 106-107, and the Herbicide Compendium, pages 127-132 (many more names have been added to the web version of the weed guide). Some herbicides now associated with many brand names are: clethodim, carfentrazone, clopyralid, diamba, halosufluron, flumioxazin, metolachlor, metsulfuron, and sulfentrazone.
Producing formulations with dicamba acid (Vision) and 2,4-D acid (Unison through Helena). May possibly combine these with glyphosate acid.
- Impact (topramezone)
New for 2006. A POST corn herbicide that was registered on August 5, 2005. Apply at 0.5 to 0.75 fl oz/A plus atrazine at 0.25 to 0.38 lb a.i./A with MSO + nitrogen fertilizer to corn from 4 to 12 inches tall. Impact is effective on pigweed species, common cocklebur, kochia, common lambsquarters, mustard species, nightshade species, common ragweed, smartweed, sunflower, and suppression of green and yellow foxtail. Impact is of similar chemistry and mode of action as Callisto. NDSU does not have any weed control data on Impact. Carryover may be an issue in ND. Below is the crop rotation restriction for Impact.
- 3 months All cereal crops
- 9 months Alfalfa, potato, sunflower
- 18 months Soybean and all other crops not listed.
ARYSTA: Old name: Arvesta.
Possible residual wild oat and foxtail control. Residual activity is dependant on the same conditions as other soil-applied herbicides, namely, the amount of herbicide that reaches the soil compared to the amount intercepted by plant foliage, amount of activating precipitation, and time of weed germination in relation to activation.
- Pendimethalin = no new registrations until re-evaluation is complete by EPA, possible future registration in wheat.
- Distinct = labeled PRE only in no-till corn.
- Pursuit Plus = labeled PRE in dry bean, dry pea, chickpea, and lentil.
- Radius (flufenacet + isoxaflutole) = PRE herbicide in corn containing the same active ingredients as Epic but with a different ratio.
Epic = 48% + 10%
Radius = 35.71 % + 4.29%
Radius will control most grass and broadleaf weeds in corn.
- Rimfire = A premix of Olympus + Silverado for grass control in wheat.
Silverado is a short-residual SU herbicide that controls wild oat and some mustard species. Olympus is a long-residual ALS mode of action herbicide that controls brome grass species. At 1.75 oz WG/A, Rimfire contains the full label compliment of Silverado and a 1/3 of the label rate of Olympus. The lower Olympus rate suppresses brome species and allows rotation to most crops the following year.
- Several active ingredients are off patent including picloram, clopyralid, and triclopyr. Several premixes of these ingredients with fluroxypyr may be registered in the future.
- Starane = labeled on several grasses grown for seed.
- WideMatch = crop rotation restriction on dry pea revised - see label.
- Starane NXTcp = a combination of fluroxypyr (Starane) and bromoxynil available in a co-pack for 2006 and labeled for use on wheat, durum, barley and oats.
Starane NXT will controls broadleaf weeds including, kochia, wild buckwheat, lambsquarters, Russian thistle, has two modes of action for resistance management, no rotational crop restrictions, excellent crop safety, a wide window of application, and can be tank mixed with some grass herbicides.
The co-pack of Starane NXT contains 1.65 gallons of Starane and 5 gallons of NXTcp. Use rates range from 20 to 40 acres per case.
- Milestone (aminopyralid) = New for 2006.
Registered in pasture and rangeland. At 3 to 7 fl oz/A, Milestone controls many noxious and perennial weeds infesting pasture and range, including thistles and composite weeds, but does not control leafy spurge. Milestone is in the chemistry as Tordon and Stinger but is a reduced risk herbicide instead of Restricted Use herbicide, has a lower use rate (fl oz/A instead of pints/A), has no volatility, no grazing restrictions, and has no ground water contamination restrictions (can spray to waters edge).
Dow has develop fact sheets on Milestone allowing spot treatment up to 14 fl oz/A allowed and where Milestone can be safely used around and under certain trees (not any legume tree). DO NOT apply Milestone over-the-top of trees. Read the label or contact your nearest Dow rep for more information.
Premixes brand names coming:
- CleanWave = aminopyralid + fluroxypyr, product for wheat
- PastureGard = triclopyr + fluroxypyr
- Surmount = picloram + fluroxypyr, high cost.
- Forefront R&P = aminopyralid + 2,4-D
Forefront is for rangeland and land which grazed where broadleaf weeds compete aggressively with forage grasses. ForeFront R&P is a complete broadleaf weed solution available for rangeland and pasture, and it allows producers to target weeds in sensitive sites that often limit the use of existing products.
Markets EPTC as Eptek which is the same as Eptam and Razencane which is the same as Eradicane.
NDSU Extension Weed Specialist