This past summer a trial was conducted to compare the efficacy of several commonly used preemergence herbicides. While the list of herbicides used does not represent every product available, it does provide comparative information on which herbicides might perform better in Oregon container nurseries.
Results in other nurseries and growing conditions may vary from those reported here. It is the author's opinion that cultural practices used in nursery production greatly affect weed vigor and herbicide efficacy. The exact cultural conditions used in this trial are listed below so they can be compared to those at your nursery and taken into account.
|Granular preemergence herbicides were evaluated for control of common container weeds. Each species was evaluated separately (different color tags).|
One gallon containers were filled with 100% coarse Douglas fir bark on July 2, 2003. Bark was amended with 1.5 lbs/yd3 of Micromax and 12 lbs/yd3 Osmocote 18-6-12. Containers were placed on a gravel container pad in full sun (bittercress and NWH were grown under 47% shade). All plants were irrigated overhead with approximately 1/2 inch water/day split in two equal cycles. Approximately one week after potting and herbicide application, containers were over-seeded with 20 seeds from one weed species. Herbicides applied at the following rates:
|Herbicide||Active ingredients||Rate (lb product/acre)|
Rates used represent the maximum labeled rate for each product.
For those interested in statistical details, containers were arranged in completely randomized design with 4 replications of 4 single container subsamples each. Weed species were randomized separately.
Results and Discussion
Results for each weed species are separated below. Click on the image or the weed name to see herbicide trial results. Click on the words 'Identify this weed' to see additional photos of each plant.
|Bittercress (Cardamine hirsuta)||Identify this weed|
|Northern willowherb (Epilobium ciliatum)||Identify this weed|
|Liverwort (Marchantia polymorpha)||Identify this weed|
|Prostrate spurge (Chamaesyce maculata)||Identify this weed|
|Pearlwort (Sagina procumbens)||Identify this weed|
|Common groundsel (Senecio vulgaris)||Identify this weed|
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