Grapes are a popular crop in warm, arid environments. Much of southern and central California is covered with rolling hills of "wine country" -- acres and acres of trellised, flourishing grape vines and orchards. Grapes are also a popular crop for home growers, who enjoy presenting home grown crops of grapes for eating and jam making. However, grapes can be attacked and damaged by grapevine leaf rust (GLR), in which case you should take some immediate steps.
Diagnose your grape vines based on their symptoms. GLR materializes as small yellow clusters on the bottom of grape leaves, and small rust-colored spots on the surfaces of leaves. Vines that are affected by grapevine leaf rust will grow weak and fall off, damaging the entire plant.
Mix a homemade remedy to treat your grapevines for rust. Mix 1 ounce of baking soda and 1 ounce of horticultural oil with 1 gallon of water in a bucket. Stir well, until the baking soda is fully mixed into the water. Using warm water may make this easier. Allow the mixture to cool to room temperature before you use it on the grapevines; spraying plants with hot or very cold liquids could damage the plants.
Spray the affected grape leaves thoroughly every 3 to 4 days until the grape leaf rust disappears.