Piercing-sucking insects most frequently discolor leaf, fruit, or stem material, making them look mottled (A, lace bug damage on jack bean and B, leaffooted bug damage on tomatoes). This is easily confused with symptoms caused by viral infections, some fungal infections, as well as some nutrient deficiencies. These pests can also cause leaf die-back which results in brown spots that can be confused with fungal or bacterial diseases. Some piercing-sucking insects can also cause leaf deformities. Asian citrus psyllids, for example, cause citrus leaves to pinch inward (C). Piercing-sucking insects prefer the underside of leaves because the leaf surface is more tender and easier to pierce. Therefore, check the underside of leaves for these types of insects.