The Fungus is Among Us

My little garden has been fairly productive, despite my hiding inside from the heat, rain, and mosquitoes. I emerge for a few minutes every couple of days to make sure everything's still alive, pick caterpillars off my tomato vines, and harvest the fruit of my springtime labors. I've continued to harvest some beans every week, and the cherry tomatoes have been tasty (I just have to make sure to harvest them while they're orange--by the time they're red the heavy rains have split the skins). My little sunflower just emerged in the vegetable garden this week, too.

I bought a sunflower "mix", so the color was a bit of a surprise.
What do you think of my little burgundy sunflower?

At the beginning of the summer I was worrying about my plants getting enough water in the heat of July. Little did I know that we would have record rainfalls! All that wet foliage is the perfect breeding ground for fungus, one of the many plant pests that can plague your garden.

I'm not talking about the mushrooms that might pop up in your backyard--those are usually harmless (to your plants, at least--I don't recommend picking one and eating it unless you're an expert). I'm talking about the fungi you might not even realize are fungi: blackspot on your roses, powdery mildew on your crape myrtles, and Botrytis on your strawberries. There are also the ones relatively unseen: the ones with crazy names (like Pythium and Phytophthora) that cause root rot, crown rot, and damping-off. From a distance it might look like your plant is dying for no reason, but upon closer inspection you'll see the real culprit.

I took a walk around my garden and discovered a few fungi affecting my plants.

Entomosporium is a common fungal disease
on Indian hawthorn.

The shot-hole fungus on my ornamental cherry
tree loves all this rain.

I'm pretty sure this is a type of fungal leaf
spot on my lemon balm.

I'm not sure what fungus is growing on my
potted palm. I'm hoping it's just feeding
on the dead leaves and won't hurt it.

As you can see, it's not always easy to identify the many fungal diseases that plague our plants. Unless you're a plant pathologist, though, it's not really necessary to know all of them. When I worked at the USDA Fruit & Nut Lab in Byron, GA, the plant pathologist I worked with would take samples of diseased pecan leaves and stick them in petri dishes to see what grew--a bacterial leaf spot or a fungal leaf spot, for example. If your plant looks diseased, the simple fact that we have so much rain makes fungus a likely candidate. So if you suspect fungus in your garden, here are some tips for treatment:

• If the damage is mostly cosmetic, don't worry about it. Many fungi, like those pesky leaf spots on Indian hawthorn, won't kill your plant. I don't like to go overboard with the chemicals, so I tolerate a certain level of disease on my plants. It's not worth spraying my huge cherry tree when I know the fungus will go away come fall. That same leaf spot affects my lemon balm every summer, but the damage is always minor.
• If the damage is minor, remove the infection. If there are spots on only a few leaves, remove the diseased leaves and throw them away (or compost them thoroughly). Clean up the fallen leaves under your plant where disease might be hiding. A lot of disease spreads by rain splashing off of existing infection.
• If there are black spots on your rose, go buy a fungicide for roses. Now. Blackspot (yes, that's actually the name) is a fungus that plagues most roses. It not only causes black spots but yellowing and defoliation. It can make your beautiful rose bush ugly fast. Buy a fungicide for roses.
• If the damage is significant, talk to a friendly professional. The nice people at your local garden center (not Home Depot or Lowe's) probably know a lot about plants. They can recognize powdery mildew in an instant, and they can recommend the best sprays for various diseases. If you don't know a good local garden center, look up your county extension agent. You can take a leaf sample down to their office, or snap a couple (close-up) pictures with your phone and e-mail it to them. They likely have a plant pathologist on staff who can ID it for you, and they'll tell you what to buy at Lowe's or Home Depot (or whether you should give up altogether and burn your plant to the ground).
• If you're using a spray, follow directions. Read all that fine print. The time of day and weather conditions can greatly affect the effectiveness of your spray. You also want to pay attention to safety warnings (like "avoid contact with skin").

Whether or not you're battling fungus now, there are things you can do to prevent future fungal wars:

• Amend your soil. There's not a whole lot you can do once your plant has root rot or crown rot except keep it from happening again. If you have heavy clay soil (common in the South), water won't drain well, and fungus can breed that can kill your roots. Mix in plenty of organic matter (such as compost) before planting to improve drainage. If you're gardening in pots, always use fresh soil (since old soil may be harboring disease) and make sure there's a hole in your pot so water can drain.
• Buy disease-free plants. Buy your plants from reputable sources, and inspect them carefully before taking them home. You don't want to bring disease home with you.
• Buy disease-resistant plants. If you don't want to spray for blackspot, there are disease-resistant varieties of roses you can buy. My 'Flower Carpet' and 'Knockout' roses, true to their care-free promise, have remained blackspot-free. My other roses have not been so lucky. It's the same with all kinds of plants--some varieties are more resistant to disease than others. When you're buying vegetables, read the seed packets to find disease-resistant hybrids.
• Clean up your garden. Those fallen leaves may look like great mulch, but they're breeding grounds for fungus. Rake them up in the fall and either bag them or compost them. If you choose to compost, make sure they're good and decomposed before using the compost in your garden.

Happy gardening!