NDSU Crop and Pest Report

Plant Science

ISSUE 11  July 10, 2003


About 10 % of the soybean fields are blooming throughout the state and in NW Minnesota this week. The beginning bloom stage or R1 stage in soybeans is marked by the plants having at least one flower on any node of the main stem. If there is still a need to spray for weeds, check the label carefully for spraying after flowering begins. There are a number of herbicides that can be used after flowering begins. These include: Assure II, Poast, Select, Basagran, FirstRate, Amplify, and glyphosate (various formulations). Always read and follow label guidelines when using pesticides.

Soybeans are at 50% bloom when an open flower can be found on every other plant in a row. Flowering, unlike maturity on soybeans, begins toward the bottom of the plant (at the third to sixth node) and then progresses upward and back downward. Branches off of the main stem will flower a few days later than the main stem. While flowering begins at the base of the plant and proceeds to the top of the plant, physiological maturity of the beans willprogress anywhere on the plant stem. Normally, soybean pods will be mature in the middle or top of the plant and down, thus remember to check pods toward the bottom of the plant when determining if harvest time has come. Flowering of soybeans is an important time in bean growth and development. At stage R2, full bloom, each plant has accumulated about 25% of its total dry weight and nutrients; it has attained about 50% of its mature height; and, it has produced 50% of its total mature node number. This later flowering stage begins the period of very rapid N_P_K and dry matter accumulation that will continue through R6. Also, during flowering the soybean plant gears up on its nitrogen fixation in order to provide for the demands of the plant. Scout for disease and insect problems (aphids) during this critical early time period of flowering.



Hail damage has occurred in some canola production fields. What kind of damage and injury can one expect?? A general rule is that the earlier the hail damage the more time to recover and the less amount of total injury and reduced yield.

Plantings in seedling stages can have stands reduced by 50% and still produce acceptable yields. An average stand of 11-12 plants/ft2 can be reduced to 4 plants per square foot before yield losses exceed 10 percent. Prior to bolting and flower development, canola can withstand hail without much economic loss. Canola with leaves that are torn and shredded suffer only partial loss, while leaves bruised on the main vein or torn and broken will be lost. Leaf area destroyed will result in seed yield loss. Seed yield losses in canola is approximately 25 percent of leaf area lost. If leaf defoliation is 50 percent, then yield loss would be approximately 12.5 percent.

Canola plants injured in late bolting or early flowering stages seldom die. The well developed root systems and ability to re-branch and develop secondary flower clusters help the plants recover. When buds or flowers are destroyed, the canola recovers rapidly by development of flowers which normally would have aborted. New branches also develop from growth buds lower down on the plant. Seed yield loss will depend on both percent leaves and branches lost. For example, if canola has 60 percent lost branches 7 days into flowering, seed yield loss is estimated at 18 percent, whereas 21 days into flowering, yield loss would be an estimated 60 percent. If hail strikes late, such as during pod filling or ripening, plant recovery is not possible. The time needed to develop new growth, flowers and mature is limited before a killing frost. Canola seed yield loss if injury occurs at the ripening stage depends directly on the loss of branches, individual pods and seed knocked out of pods. Severe hail losses have occurred in canola swaths.

Duane R. Berglund
Extension Agronomist  



Nobel Peace Laureate Norman Borlaug says the 21st Century challenge to agriculture will be producing sufficient supplies of food to sustain the world's continued population growth. "The world has the technology, either available or well-advanced in the research pipeline, to feed 10 billion people," said Borlaug, who delivered the keynote address during the second day of the Ministerial Conference and Expo on Agricultural Science and Technology in Sacramento. "Extending the Green Revolution to the Gene Revolution will provide a better diet at lower prices to many more food-insecure people." Agricultural scientists have the ability to meet this challenge through continued research and development of technology, including biotechnology, that can expand the yield potential of crops to improve resistance to insects and disease, resistance to herbicides, nutritional quality and abiotic stresses.  

Source: Western Farm Press

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