VOLUME 22, NO. 16                                                                                                                                                                    August 28, 2008

FINAL AG ALERT FOR 2008 

This will be the final issue of the Ag Alert newsletter for the 2008 growing season.  We hope we have provided you with current and timely information.  Thanks to all the faithful readers, we look forward to continuing this next spring.  We are open to any suggestions you have that will improve the content of this newsletter.  Contact us at 701-780-8229.

DRY BEAN DESICATION

Glyphosate is labeled on edible beans for pre harvest weed control. It�s good to be reminded each fall that glyphosate is NOT labeled as a crop desiccant. Dry beans are a direct food source meaning they can go from the field to the final consumer. A concern of many in the bean industry is glyphosate residue being found in the beans due to improper timing of a glyphosate application. It is important to wait until the bean pods have turned a yellowish color and have a leather texture before making an application of glyphosate. The bean should be in the hard dough stage and 30% or less seed moisture. Application before this could lead to glyphosate residue in the bean itself. It is not recommended to apply glyphosate to dry beans grown for seed because reduced germination and/or vigor may occur. There are various glyphosate trade names and formulations available. Be sure to read and follow the label directions. Glyphosate has a seven day pre harvest interval (PHI).  Herbicides labeled for desiccation include paraquat (Gramoxone Inteon, and Gramoxone Max), carfentrazone (Aim), and flumioxazin (Valor). Application timing of these herbicides differs when comparing to a glyphosate application. Bush type beans should have 30% green leaves remaining while vine type beans should have 40% green leaves remaining before application with at least 80% of the pods a yellow brown color. Thorough coverage is essential with a contact herbicide to help avoid a second application. The pre harvest interval for paraquat is 7 days, Aim 3 days, and Valor 5 days.  For more information consult the 2008 North Dakota Weed Control Guide circular W-253. It is also available on the web at www.ag.ndsu.edu/weeds.  Remember with all pesticides to read and follow all label directions. The label is the law.

CROP ROTATION FOLLOWING VALOR APPLIED AS A DESICCANT

Valor has received full federal registration for use a desiccant in dry edible beans. Information on application is contained in the label and on page 29 in the ND Weed Control Guide. Valor has performed equal or better than other registered dry bean desiccants. Like other desiccants, Valor requires maximum sunlight and temperatures for maximum activity. Valor is not a panacea for dry bean desiccation and growers should not expect Valor to desiccate dry beans as well under cloudy and cool weather. Valor has provided greater desiccation in these less than optimum conditions than the other products.  Apply Valor at 1.5 to 2 fl oz with an MSO adjuvant.  Adjuvants containing MSO provides the greatest enhancement of Valor. If an applicator chooses a petroleum oil adjuvant (COC) instead of an MSO then performance will decrease.  Valor will desiccate dry beans but will not desiccate weeds.  Valor can be applied with gramoxone for weed desiccation.  MSO adjuvant will enhance both Valor and gramoxone.  What will be the crop rotation restrictions for Valor applied as a dry bean desiccant as compared to a preemergence application applied in the spring? This is important in that growers want to have flexibility in choosing which crop to plant the next year. Supplemental labeling shows that any crop can be planted the following season (>4 calendar months) after Valor applied as a PRE after crop planting or as a desiccant at 2 oz/A or less. Valent, through research conducted in ND, has found some response from canola in no-till conditions. Valent may increase the restriction for canola on the next label submission.  They found no canola response in conventional tillage systems.

RUST ON DRY BEANS APPEARINIG IN NORTH DAKOTA

The appearance of rust on dry beans has been sporadic this year, but is severe in localized areas in the state. Rust can cause yield loss when severe.  Rust can be identified by small (about 1/8 inch) reddish brown pustules on leaves. Reddish-brown spores (urediniospores) are produced in the pustules, which can easily be rubbed off with your finger. The ability to rub off spores distinguishes rust from other diseases such as bacterial blights. Rust can progress quickly in fields when temperatures are moderate, and when heavy dews occur in the mornings. As the season progresses, the rusty-colored spores in the pustules will be replaced by black spores (teliospores), which are hard to rub off. Once the color change of the spores is apparent, disease progression will grind to a halt.

Fungicides can be used to manage rust, and several fungicides are available for rust control, including Folicur, which just received a Section 3 � Full registration for management of rust on beans. The supplemental label is available at http://www.cdms.net/LDat/ld6AK031.pdf.  The supplemental label must be in your possession if a fungicide application is made. Other fungicides can be found in the 2008 ND Field Crop Fungicide Guide (PP-622) available at http://www.ag.ndsu.nodak.edu/extplantpath/.  If fungicide application is something you�re considering, it is vital to keep a couple things in mind. First, be certain your beans are infected with rust, and not something else. We are observing lots of bacteria diseases throughout the state, which cannot be controlled with fungicides.  Secondly, as the season progresses, the likelihood that new rust infections will cause yield loss decreases. As the weather turns cooler rust will develop more slowly and eventually cease when teliospores are produced. Additionally, as beans mature, rust is less detrimental to yield, and thus, fungicides are not economic.

SOYBEAN APHIDS MOVING FIELD TO FIELD AND WHITE DWARFS PRESENT

In mid to late August, soybean aphids typically move around from field to field as soybeans mature. It�s easy to find little white aphids called �White Dwarfs�.  These are living, feeding and reproducing soybean aphids and should be included in your total plant population counts when assessing economic levels of soybean aphids.  Research from University of Minnesota indicates that white dwarf aphids (those typically on lower leaves) live half as long and their lifetime fecundity is reduced 70% compared to the �mountain dew� colored soybean aphids (source: D. Ragsdale). Thus if the population is only comprised of white dwarf aphids, the economic injury level (population of aphids that cause a yield loss) would probably not be reached in 7 days. An economic threshold (population of aphids that triggers an insecticide) has not been established for plants with primarily white dwarfs; however, it is obviously higher than 250 aphids per plant.

The other thing to keep in mind is that we are now past the critical day length (mid-August) and once soybean aphid experiences temperatures below 45F, the next generation will be sexual. Winged gynoparae will fly to buckthorn and leave soybean fields.  Remember, to continue scouting soybean fields for aphids until R6 or full seed!  No insecticide sprays are recommended in R6 or later R7 (beginning maturity) as there is little or no economic return from treating.

WINTER WHEAT PLANTING TIPS

 Planting date: The optimum planting date for the northern half of the state is September 1-15 and for the southern half September 15-30. The last date that winter wheat can be planted will depend on the weather. The seed must germinate in the fall so that the crop will be vernalized in the spring. A larger plant will over winter better than a seedling or a sprouted seed.

Planting depth: Adequate moisture for establishing winter wheat is often a concern as the soil profile is usually depleted of moisture in the fall. If there is little or no moisture in the soils surface, planting shallow (1 to 1.5 inches deep) and waiting for rain is recommended.

Seeding rates: Generally a seeding rate of 900,000 to 1 million viable seed per acre is adequate. Higher seeding rates may be appropriate if planting late or when planting into poor seedbeds.

Plant in to crop residue: The best winter survival is achieved when winter wheat is no-till planted into standing crop residues that are able to catch and retain snow.

Variety selection: In addition to agronomic characteristics such as plant height, yield, and disease and lodging resistance, also carefully consider the winter hardiness of a variety.