2012 Herbicide Update

The 2012 North Dakota Weed Control Guide lists several new herbicides for weed control in small grains. One of them is Axial Star. Like Axial XL and Axial TBC, it contains pinoxaden and a safener in addition to fluroxypyr (Starane). As a post emergent herbicide it will give good weed control on several grassy weeds, some broadleaf weeds and kochia. The Axial line of herbicides is marketed by Syngenta.

Bayer Crop Science has released a new product called Huskie Complete. It contains the same herbicide as Huskie (bromoxynil and pyrasulfotole) plus thiencarbazone which is a new active ingredient introduced to North Dakota. Thiencarbazone is a very effective grass herbicide making the combinations an effective herbicide for a broad spectrum of weeds in wheat. Husky Complete is not intended for barley.

Olympus is another product of Bayer Crop Science. Pre-registration is pending for use on spring and winter wheats. It is not for durum or barley but is very effective on bromes, wild oat and mustard species. Osprey is another Bayer product which contains mesosufuron, the same active ingredient as Silverado. It is active on bromes, wild oats and Persian darnel but registered for use on winter wheat only. Rimfire Max is a popular herbicide on small grains. It contains the combined active ingredients of Olympus and Osprey.

For field pea and chickpea, the Sharpen rate has been increased to two fluid ounces per acre. For sunflowers, the herbicide Broadaxe (Dual Magnum + Spartan) is registered. Because of resistance in new sunflowers lines the rate of Beyond will be increased to six fluid ounces rather than four.

In shelterbelts, a new product called Alion has been released by Bayer. It has a new active ingredient, indaziflam, which has a mode of action which affects cellulose development. It is to be used as a pre-emergent application before weeds have emerged in the spring. This product is claimed to have good residual activity extending grass and broadleaf weed control well into the growing season.

Much information is contained in the North Dakota Weed Control Guide which is authored by many agronomists and weed researchers at North Dakota State University. It remains available free of charge at my office 701-577-4595 or at http://www.ndsu.edu/weeds.

Growth Regulators Reduce Fruit Production

Fruit on trees adds color and interest to the home landscape. However, when mature the fruit can be messy and adds to the maintenance of the yard.

At one time, the fruit on trees could be thinned by spraying the tree with the insecticide Sevin approximately two weeks after the flower petals had fallen. The Sevin label has been changed making it illegal to use for this purpose.

Some of my colleagues tell me there is a better product available. It is sold as Florel Fruit Eliminator. It is based on a growth regulator called ethephon and must be applied to trees when they are in full bloom. Ethephon releases ethylene which is a naturally occurring plant hormone causing fruit to drop in its earliest stages before it sets.

Effectiveness of fruit elimination products seems to vary. Research at Kansas produced mixed results when treating crabapples. Some varieties responded quite well to the treatment while others showed no effect. Generally, fruit eliminator may not be satisfactory on small red fruited varieties of crabapples.

It is recommended to apply ethephon products prior to fruit set at the mid to full bloom stage. This is going to require close observation. Applications to early or too late will be less effective.

I do not have personal experience with any of the growth regulators used for fruit elimination. From the information received of co-workers and from research literature I sense it is unrealistic to expect complete elimination of fruit.

Black Knot On Cherry Trees

Many trees of the Prunus species are susceptible to a fungal disease called black knot. This includes chokecherry and plum. One of the most popular chokecherries found in residential areas of Williams County is the Canadian Red Cherry. It is also known as Schubert chokecherry. Although it bares reference to our northern neighbor it is a variety that was released by the Oscar Will Nursery, Bismarck. It is a selection with reddish purple foliage. In the spring and throughout most of the summer new growth emerges with green leaves. As the leaves harden they turn to a purple color.

The black knot disease usually requires two years to complete a life cycle. We usually recognize its presence by the second spring after infection when new fungal spores are produced. The fungal organism invades the vascular system located just under the bark. In this area are the xylem and phloem vessels which transport water and energy nutrients. As the fungus populates, it creates an olive-green swelling on the twigs or branches reducing the tree’s ability to transfer nutrients beyond the infected area. By the second spring after infection the swellings become black, rough and woody knots that are two to three times the diameter of healthy branches of the same age. Spores from those knots can be transferred to new shoots or wounds on older branches by wind or rain.

Removing the knots and 3-4 inches of healthy wood below the knots is a general recommendation. Joe Zeleznik, NDSU Extension forester, suggests a dormant spray of lime sulfur after removal of the knots.

Over the years, I have seen trees react quite differently to the disease. Some have survived severe infections while others have not. Some trees seem to have a resistance to the fungus.