Biological insecticide. Controls Worms and Caterpillars on Fruits, Vegetables, Ornamentals and Shade Trees. Easy-To-Mix Liquid Concentrate or Ready to Spray For organic gardening. This highly effective, organic insect killer liquid concentrate is a must-have for any gardener or plant enthusiast. Made with naturally occurring bacteria, Monterey B.t. targets and eliminates a wide range of harmful insects, including caterpillars, moths, and beetles.