If you have grapevines, the last thing you want is to share them with beetles. Beetles can do a tremendous amount of damage as they munch on the vines and leaves, and the grubs can work underground as they dine on the roots, stunting the growth of the plants. Beetles can be very difficult to eradicate, but a number of tactics can help, and if you're persistent, you can keep beetles from destroying your grapevines.
Go beetle hunting early in the mornings when the beetles are slow moving. Arm yourself with a bucket of soapy water, and shake the beetles into the water. The soap film on top will prevent them from escaping.
Mix an organic beetle repellant spray. Combine two hot chili peppers and three large garlic cloves in a blender. Strain the larger bits out of the mixture, and stir in 2 drops of dish detergent and 2 drops of cooking oil. Pour the garlic and pepper mixture into a spray bottle. Spray it on the grapevines very generously early in the mornings. To kill beetles, they must be coated with the spray, so a light misting won't work.
Remove weeds under and around the grapevines, and keep the area free of leaves and debris that will provide a hiding place for beetles. It will also remove a place for beetle larva to hatch.
Cover grapevines with a large piece of cheesecloth or netting. Sheer curtains will also work and can often be purchased very inexpensively at thrift shops. Leave the protection on the grapevines for 2 to 3 weeks, and remove it when the peak of the beetle invasion has passed.
Encourage birds to visit your yard, and they'll dine on the beetles. Plant some brightly colored flowers, and provide the birds with a birdhouse and a bird bath.