AgAlerts 2003 From Griggs County
By John Swenson, Griggs County Extension Agent

Issue # 4, June 5, 2003

Fungicide Treatments for Spruce Trees
Rolling Soybeans
Leafy Spurge Treatments
Alfalfa Harvest
Small Grain Disease Forecasting Models

Fungicide Treatments for Spruce Trees

Most Colorado spruce trees are showing signs of new growth. Those that have been affected by Rhizosphaera needlecast, now is the time for treatment. Management for Rhizoshpaera needlecast requires two applications of a chlorothalonil fungicide. Timing of the fungicide application is important - the first should be made about the time the new shoots are approximately ½ inch expanded, or roughly when the lilacs are blooming. The second application should be made about 3-4 weeks later. It is critical to do both applications to get the disease under control in a tree. Good disease control will likely require two applications of the fungicide for two consecutive years.

Rolling Soybeans

Rolling fields can be done either PRE or POST emergence of soybeans. Advantages of rolling PRE emergence are low potential for crop injury but could result in soil-surface crusting or soil erosion. Rolling fields POST can cause plant injury including crushed leaves and cracked or broken stems. The growing point on a soybean plant is above the cotyledon leaves. If a plant is broken below the cotyledon leaves the plant will die. Injured plants may be more susceptible to lodging or disease. To best avoid too much injury, roll soybeans between the cotyledon stage and first trifoliate stage. Also, rolling during the warmest part of the day on less turgid plants will lessen injury.

Leafy Spurge Treaments

Rod Lym, NDSU Weed Scientist, has found a combination of of herbicides that extend leafy spurge control for more than one year. This combination is as follows:
Tordon @ 1 pt/A + Plateau @ 4 fl oz/A + 2,4-D @ 1 qt/A + MSO type adjuvant @ 1 qt/A

Alfalfa Harvest

The timing of harvest for alfalfa use to be determined by maturity stage. Current research has shown that plant height has more influence on forage quality than maturity stage. If your objective is to get prime hay in the bale, harvest must occur around 25 inches of growth in early years like this. Plant maturity stage will vary, but it could be as early as late vegetative to very early bud. Alfalfa fields in this area are reaching this height. If winter injury was severe, forage quality should be sacrificed for stand maintenance. Let alfalfa in the uninjured area reach about 25% bloom so that injured areas can regain some plant vigor prior to harvest.

Small Grain Disease Forecasting Models

The NDSU Small Grain Disease forecasting Model is up on the Web. The site is as follows:
http://www.ag.ndsu.nodak.edu/cropdisease/cropdisease.htm
This site is designed to identify weather conditions favorable for disease development using data from the NDAWN weather stations around the state. Forecasting models are available for tan spot, Septoria Blotch, leaf rust and Fusarium head blight (Scab). Information supplied will help producers determine whether a fungicide application is needed.