ISSUE 6 June 19, 2008
IMPACT HERBICIDE - REDUCED CROP ROTATION RESTRICTIONS
The Impact herbicide label now includes the reduced use rate of 0.5 oz with a 9-month plant back to soybeans as opposed to the 3/4 fl oz rate which would require an 18 month restriction on soybeans. The new Impact label also adds four new weeds: green foxtail (in addition to yellow foxtail), dandelion, powell amaranth (similar to redroot pigweed and well established in ND), and marestail.
NEW HERBICIDE FOR SOYBEAN
Authority Assist is a premix for preemergence broadleaf weed control in soybean. The ingredients are sulfentrazone (Spartan) and imazethapyr (Pursuit). Authority Assist has rate recommendations at full rates of 6 to 12 fl oz/a depending on soil type and organic matter, and at reduced rates of 4 to 6 fl oz/a. The reduced rates are intended as a foundation treatment to suppress early-season weeds before a glyphosate application in Roundup Ready soybeans. The 6 fl oz/a rate provides the equivalent of 6 fl oz/a Spartan and 2 fl oz/a Pursuit. With this premix, control or suppression of lambsquarters, nightshade, pigweed, smartweed, velvetleaf, and waterhemp should be expected along with suppression of foxtails. Common and giant ragweed are weeds that may not be suppressed well. Because Authority Assist contains imazethapyr, certain rotational crops are limited. Rotational intervals include wheat at 4 months, barley and tobacco at 9.5 months; field corn, peas, and snap beans at 10 months; alfalfa at 12 months; oats and sweet corn at 18 months; and potatoes at 26 months.
AXIAL XL HERBICIDE LABEL CHANGES
• Do not graze livestock or harvest forage for hay from treated wheat and barley for a minimum of 30 days following application.
• Do not harvest grain for 60 days following application.
• Do not apply both Discover and Axial products to the same crop in the same season.
• Wheat and barley straw may be fed to livestock 60 days after application.
CALLISTO LABELED ON FLAX AND PEARL MILLET
Callisto is now labeled only as a soil-applied treatment on flax and pearl millet. The supplemental label contains information about crop injury if applied postemergence. The label rate is 6 fl oz/A.
CALLISTO LABELED ON OATS
A supplemental label for Callisto has been posted on CDMS that allows preemergence or postemergence applications for broadleaf weed control in oats. This label is for oats grown for seed, not for oats underseeded with alfalfa. The preemergence rate is 6 fl oz/a and the postemergence rate is 3 fl oz/a. Postemergence applications need crop oil or surfactant to control emerged broadleaf weeds. The addition of ammonium sulfate or 28% UAN will improve weed control, but may also increase the risk of injuring the oats. The preemergence application should provide greater crop safety than postemergence applications. The spectrum of weed control will be the same as when Callisto is used in corn.
PERMIT HERBICIDE REGISTERED IN DRY BEANS
Last was a banner year for common ragweed and it was especially a problem in broadleaf row crops, including dry beans. Permit controls most large-seeded broadleaf weeds including cocklebur, marshelder, wild mustard, and ragweed species. Permit was developed as a POST corn herbicide by Monsanto and now Gowan owns the marketing right. Gowan has also expanded the label to include use on additional crops, including dry edible beans. Permit is labeled for PPI and PRE use in dry beans at up to 0.67 oz product/A. NDSU has a limited database on PRE weed control.
Permit is rated "Good" across universities for common ragweed soil-applied (PRE or PPI). Permit + Eptam is rated as (Very Good). Eptam has lost favor for weed control in ND because of the quickness of incorporation and deep incorporation required. Deep incorporation (PPI) of Permit with yellow herbicides (Treflan, Sonalan) or Eptam may dilute the product too much and lead to less efficacy. Yellow herbicides are generally rated poor on large-seeded broadleaf weeds anyway. Permit + Dual is a little more variable based on university ratings.
A logical program for common ragweed control in dry beans would be Permit PRE followed by Reflex POST if escapes occur. These programs would give different mode’s of action, which is good because ragweed resistance to Permit (ALS) has been documented.
COCKLE/NIGHTFLOWERING CATCHFLY CONTROL
The Huskie label should show control of nightflowering catchfly the same as white cockle. Bayer has conducted research to confirm control of both nightflowering catchfly and white cockle. Huskie at 11 oz/A will provide 90 to 95 percent control of both of these species. The activity may be slower on white cockle than some of the other species on the label such as lambsquarters, etc. Complete control on white cockle may not be expected until 21 to 28 days after application.
Extension Weed Specialist