Hydroponics is the technique of growing plants in water without soil. Because of a lack of space or fertile soil, farmers worldwide have been using this type of gardening for centuries. One of the earliest hydroponic gardens was the Hanging Gardens of Babylon. Although diseases in hydroponic gardens occur less than in dirt gardens (because there's no soil for bacteria to grow), hydroponic plants do battle some problems with fungal diseases and pests.
Powdery mildew, a fungal infection, is a problem because of the constant moisture of hydroponic plants that causes various types of molds. Common signs of this fungus are the powdery white spots found on plant leaves. Some of the plants most vulnerable to powdery mildew are squash, cucumbers, pumpkins and roses. This fungus is caused by damp weather combined with hot summer temperatures where plants grow too close together. Plants that receive too much shade are also at risk. Rather than harsh chemicals, one can spray leaves with a mixture of ½ cup of milk with ½ cup of water, according to Hydroponics at Home.com. Treatments should be done several times daily.
Black mold is a dusty black fungal growth that occurs mostly on garlic and onion plants. If not treated, this fungus will take over an entire fruit and turn it black--making it susceptible to many other secondary infections. Fortunately, black mold is preventable. It normally occurs because vegetables have been improperly stored in damp, high-temperature conditions. This fungal infection can also enter vegetables through wounds. Although chemicals are somewhat effective, the best way to prevent black mold is to use seeds treated with fungicide and then to harvest in dry conditions.
Spider mites are yellow, green or red microscopic insects that form cobwebs. These pests, which are a common hazard to hydroponic plants, multiply at a disturbing rate, killing crops quickly. They destroy plants by sucking out the content of plant cells. Some of the first signs of a spider mite infestation can be seen in clusters of dead spots appearing on plant leaves. One effective treatment is to wash an infected plant's leaves with warm soapy water and then spray the leaves with an insecticide.
Aphids are tiny oval-shaped insects with lightly colored bodies. These pests are known for leaving a sticky residue on plant leaves. They suck on plant leaves and are found in clusters. Aphids can be washed off plants or controlled by spraying a solution of water, ground hot pepper seeds and soap. The spray should be applied three times day for three days, followed by two times daily for next five days, according to Indian Hydroponics.com.