Tomato plants are susceptible to many pests and diseases. You must check your tomato plants on a regular basis to keep them healthy until you are ready to harvest them. One pest that often attacks tomato plants is the white fly. The white fly has piercing-sucking mouth parts that cause damage to the tomato plants. If you spot white flies on your tomatoes, you will need to get rid of them.
Vacuum the whiteflies off of the tomato plants. Make sure you check underneath the leaves. Remove the vacuum cleaner bag as soon as you are done, and set it in the freezer for 24 hours to kill them. Toss the bag out with the trash.
Smear a layer of petroleum jelly onto a small yellow poster board. Super glue a thin wooden stake to the back of the poster board, and set it in the middle of your tomato garden. The whiteflies will be attracted to the yellow poster board, but will get stuck to the petroleum jelly and die.
Spray the whiteflies daily with your garden hose. The water will drown the adults. If you make this a habit, eventually there will be no more adults to lay eggs. Once the remaining eggs hatch, you will kill them off with the water before they have time to lay their own eggs. The whiteflies will then be completely eliminated.
You can make your own insecticidal soap out of dish soap and water to spray on the tomato plants.
Not all chemical insecticides will work against the white flies, and you don't want to use harsh chemicals around a vegetable you plan on eating.