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At potato harvest, they areAt potato harvest, they are killing the vines to terminate the growth of the tubers to control their size and set their skin which reduces bruising during harvest. This process also reduces insect issues and disease. They are probably applying an herbicide to help vine kill which is best applied at dusk with high volumes of water. This allows the product to penetrate the leaves and stems before being activated by the sunlight the following day. Hope this helps answer your questions!

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