The sight of nightshade's purplish/black berries in a "food grade" soybean crop is every producer's worst nightmare. They stain the seed and dramatically reduce the value of the crop. In theory, you would kill uncontrolled nightshade prior to harvest with either a herbicide (i.e. Reglone, glyphosate) or mother nature (i.e. a frost), the berries would drop to the ground, never go through the combine and the seed would be left unstained. Unfortunately this is a theory, and reality shows us otherwise. Around the 12th of October, a significant frost was observed in Waterloo/Wellington county which resullted in a number of annual weed species "dying off" in soybeans.
The one notable exception was nightshade. Even though the leaves were finally starting to wilt after 4-5 days of consecutive frosty mornings, the berries were still very much attached to the plant. Plant dessication with herbicides has proven equally ineffective as many berries will still cling to the plant even after it has died off. The average plant in this field had 280 berries with each berry averaging 60 seeds for a total of 16,800 seeds per plant.
If you had Eastern Black Nightshade in a field of "food grade" soybeans it's either because: 1) You didn't know it was there in the first place or 2) You knew it was there, but the herbicide was ineffective Public trials conducted by the University of Guelph (Sikkema, Swanton and Tardif) have shown that following herbicide programs provide greater than 80% control of Eastern Black Nightshade in soybean. 1) Pursuit (PRE or POST - 99% visual control) 2) Lorox L (PRE - 99% visual control at the highest labeled rate) 3) Dual II Magnum (PRE) followed by Reflex (POST - 98% visual control) 4) Dual II Magnum (PRE, highest labeled rate - 87% visual control) 5) Frontier (PRE, highest labeled rate - 80% visual control) If you have used one of the above herbicide treatments and they did not provide adequate control, it may be possible that the population of Eastern Black Nightshade in your field is resistant.
The University of Guelph can test this population for you to determine if it is herbicide resistant.
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