Bacteria are minute plants, which can cause rotting, wilting, and the forming of galls.
Fungi, which are usually visible to the naked eye, cause rusting, spotting, mildewing, and damping-off. Moisture, warmth, and humidity generally encourage both. Control these problems with the proper fungicide or by removing and destroying diseased plants. Purchase disease-free or treated seeds and plants. Crop rotation, staking, mulching, and adequate soil drainage are also important.