AgAlerts From Griggs County
By John Swenson, Griggs County Extension Agent

Issue # 2 June 6, 2000

Leaf Rust Present in Winter Wheat

    Low levels of leaf rust were found in an area (Stutsman County) winter wheat field on June 1. Producers are encouraged to monitor winter and spring wheat fields for leaf rust, especially if susceptible varieties are grown. Most winter wheat varieties are susceptible to rust, with the exceptions of Elkhorn (moderately resistant) and Ransom (resistant). Spring wheat varieties rated as susceptible to leaf rust include 2375, AC Barrie, 2398, and McNeal. Numerous other varieties are moderately susceptible to rust. Refer to NDSU Extension Service circular A-574, 2000 ND HRS and HRW wheat variety selection guide for leaf rust and other foliar disease ratings.

    What impact does leaf rust have on yield? Based on Kansas State University data, wheat in the flowering stage with 10% severity on the flag leaf is predicted to cause 10% yield loss, 40% severity may cause 20% yield loss, and 100% severity may cause 35% yield loss. As wheat reaches later growth stages the impact of leaf rust on yield is reduced. For example, at the soft dough stage, 10% rust severity on the flag leaf is predicted to cause 1% yield loss, 40% severity may cause 4% yield loss and 100% severity may cause 10% yield loss.  Fungicides cleared for use include any of the mancozeb products, Tilt, Quadris and Bayleton 50 DF.

Soybean Chlorosis

    Soybean chlorosis is problem that we see to some extent every year. Chlorosis associated with iron deficiency does not appear until the first trifoliate leaves appear in the plant. There are several factors which contribute to this problem. The first important and undisputed factor is the presence of free carbonates, particularly bicarbonate which is a product of the combination of water and carbonate minerals in the soil. Bicarbonate solubility is low, and contrary to logic increases in concentration as the soil becomes wet. So in dry years and dry periods, chlorosis can be relatively minor, because bicarbonate levels interfering with plant uptake of iron are low. As the soil becomes more moist, bicarbonate concentrations increase and the plants become less able to take up iron. 
    The phenomena of wheel tracks being yellow or green compared to the rest of the field is probably the result of soil wetness under the tracks. In dry conditions, the soil tends to be more moist under tracks because of capillary pull of water into the track similar to the press wheels of a planter pulling moisture into the seed zone. More moisture, more bicarbonate, more chlorosis. In wet years, wheel tracks and compacted areas tend to dry first, thence less moisture, less bicarbonate, green tracks. The following factors are stress factors that make the plants less able to take up iron in adverse circumstances; cool weather and soluble salts. Cool weather slows down plant systems, including iron uptake and plants tend to increase in chlorosis during cool periods when soils are moist and carbonates are present. Soluble salts have also been shown to be a major factor in contributing to the presence of chlorosis with supposedly iron chlorosis tolerant varieties. Often, carbonate levels and soil moisture are similar, but the presence or absence of salts has been the difference between whether chlorosis appears or not.

Griggs and Barnes County Spotted Knapweed and Leafy Spurge Tour

    The weed boards of Griggs and Barnes Counties have lined up a tour to help landowners identify and control spotted knapweed and leafy spurge.  If you think that leafy spurge is a problem, wait until you have spotted knapweed problems.  The following is a tentative agenda.

SPOTTED KNAPWEED AND LEAFY SPURGE TOUR
WEDNESDAY, JUNE 28, 2000
BARNES AND GRIGGS COUNTIES

9:00 am Meet at Sibley Crossing Parking Lot
9:30 am 1st Stop - Wilfred Kunze Cooperator 
    *Rod Lym - "Know Your Knapweeds"
    *Kevin Sedvig - Range Evaluation and Species Identification
11:00 am 2nd Stop - Katie Olson Landing
    *Don Mundal - Leafy Spurge Control Beetle with flea beetles and Spurge Resurgence
    *Rod Lym - Leafy Spurge Chemical Control Practices
12:30 pm Sponsored Meal - Bob Lee Farm
1:00 pm - 3:00 pm Open Leafy Spurge Flea Beetle Collection

Leafy Spurge Flea Beetle Collection Day

    The Griggs County Weed Board has scheduled a collection day for leafy spurge flea beetles on Monday, June 12th at Butte Michaud, ten miles north of Cooperstown beginning at 10:00 am.  At this time we are not sure of the populations that survived the open winter.  Reports from Barnes County say that they are finding the populations as in past years.  So future collection days will be planned according to the number of beetles we are finding.  The weed board has sweep nets available for use.  If you have your own sweep net, please bring it.  Also, bring a cooler to transport the beetles and if available, a frozen container to keep the beetles cool.  Ice is not the product of choice due to it will melt and drown the beetles.  If you have any questions, please contact the Extension Office at 701-797-3312.

Ammonium Thiosulfate With Poast plus oil

    Call have been received by NDSU weed specialists concerning the mixing of the herbicide Poast and ammonium thiosulfate (a liquid sulfur material) to be applied on canola.  DO NOT USE THIS COMBINATION.    John Lukach, Agronomist at the Langdon R/E Center stated emphatically that ammonium thiosulfate should not be used with Poast or any herbicide product requiring oil additive.  The combination will burn the crop to the ground.  Even products using extra surfactant that might thin the cuticle of the canola plant, should be avoided.
    The larger the canola is prior to bolting the less damage although it still maybe very severe and can reduce yields.  Best option is to apply the ammonium thiosulfate first with water and then to apply the grass herbicide plus oil several days later.  This would reduce the chance of cuticle damage or removal resulting in less fertilizer burn.  Usually 3-5 gallons of water to bring the total to 20 gallons per acre to reduce the risk of fertilizer burn.

Please Contact Our Office For Additional Information
E-mail: griggs@ndsuext.nodak.edu
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