Horrors, there are holes in the hosta leaves. The phlox leaves have white spots on them and there is some yukky looking yellow stuff on the mulch. Don’t panic. The holes are probably from slugs. In other plants it is often grasshoppers. White leaves mean downy mildew and the yukky stuff is most probably vomit mould. None of these things need the gardener to be tearing his-her hair out.
Keep your plants healthy. Stressed plants are those that have been over or under watered, over or under fertilized, or have a recurring disease (like powdery mildew), and are more apt to be attacked by insects or other diseases. A stressed plant produces compounds that may even attract insects.
Practice good garden hygiene. Be religious about dead heading. Remove any dead or diseased stems or leaves. Give each plant elbow room. Plants living too close together get sick more often than plants that have good air circulation. In the fall, remove any dead foliage that may conceal fungal pathogens.
Take a stroll around the gardens at least every other day. This way, you will notice insect damage, mildew appearing, aster yellows or other problems and deal with them before they get out of hand.
Water in the morning if at all possible, and never overhead. You will lose less moisture to evaporation and leaves will dry more quickly, preventing or at least discouraging wilts, blights and leaf spots.
Mulch! Mulch keeps fungal spores that live in the soil down there where they belong, not on your plants. It also keeps the soil cool, prevents pounding rain from compacting the soil, holds moisture, and prevents weed seeds falling on it from infesting the garden. They either die since they can’t root well or, if they don’t, are very easy to pull out.
Buy Listerine by the gallon. Used to disinfect tools, even shovels, Listerine mouth wash kills most pathogens and doesn’t damage cutting edges like bleach or alcohol does. Plant diseases like Virus X in hostas, black knot in cherry and plum trees, and fire blight in apples, for instance, are spread on cutting edges of tools. Disinfect a tool after each cut.
And, if you have a plant that gets sick every single, stinking year, throw the darn thing in the garbage and plant a resistant variety instead. Monarda and phlox are notorious for getting powdery mildew if there are two drops of dew in the air. The newer varieties are resistant and often prettier plants. Or, you can plant some other plant entirely.
If you have had problems with tomatoes, look for the letters VFNT after the variety name. This means the plant is resistant to verticillium, fusarium wilt, root knot and tobacco mosaic virus. This doesn’t mean you can have a smoke then harvest tomatoes. The smoke left on your fingers can easily infect a damp leaf on the tomato, thus infecting the whole plant. The plant is resistant, not disease proof.
Finally, be tolerant. A few holes in leaves, a yellow leaf or a stray insect in the garden doesn’t mean the whole plant is on the way out. Most plants can stand a bit of damage, and no garden is ever perfect. Just be vigilant and never let things get out of hand. A stroll through the garden before it’s hot enough to fry frogs will usually be enough to nip most diseases in the bud.