Bugs & diseases are airborne and can be carried on your clothes or your pets. If you have a plant that is sick or has bugs outside, you or your pets can transfer the bugs & or disease inside. You should always change clothes & shower before you start gardening or you are taking a risk of transferring pest to your plants. Another BIG reason customers keep getting bugs & diseases is they do not do enough treatments when they get the problem the first time. When you get spider mites or white flies you have to continue treatments; even after you do not see the bugs, for at least 2 weeks after as eggs will keep hatching. It is better to do a preventative treatment for disease than it is to do a treatment because you have a sick plant. Sick plants mean poor yields. Bugs can not only carry disease but they can hurt your plant so much it gets a disease (it is like when you smash you foot you catch a cold because your body is spending most of its energy fixing your foot).