This sould be alright...
Preen Vegetable Garden Weed Preventer contains corn gluten meal. It is an organic by-product of the wet-milling process, and is sold as a feed ingredient for cattle, poultry and other species of livestock. It has been used in fish food for commercial fish production. Corn gluten meal is also a primary component in some dog food products. Corn gluten meal is 60% corn protein, and it is this high level of protein that inhibits the growth of seeds.
Preen Vegetable Garden Weed Preventer is an organic product that is safe for use around children and pets. As with any product, allergic reactions can occur in some individuals. The product prevents annual weeds from growing in vegetable gardens, flowerbeds, around trees, shrubs, and ground covers for up to 4 to 6 weeks.
But I'm not sure that the hops will be able to handle it. It way kill them as well. I have never used any weed control or pesticides, so I guess I don't really know.