Tomato plants are susceptible to several different types of bugs, but the most common insects found under the leaves of a tomato plant are aphids. Aphids are one-eighth inch long and can be brown, red or black in color. Aphids feast on tomato leaves by sucking out the juices from the leaves. This damages the leaves, and even leads to their death. It is important to get rid of aphids and other small pests as soon as you notice them on a tomato plant.
Pour either the liquid soap or the canola oil in a small bucket.
Add the water to the bucket and stir the two ingredients.
Fill a spray bottle with your homemade insect killer.
Spray the insects on your tomato plants first thing in the morning. Insects are more sluggish early in the morning.
Repeat each morning until you no longer spot insects on the tomato plant leaves.