Preventing Club Root

Club root is a fungus-like mold that causes bulging, malformed roots on vegetables in the cabbage family (cabbage, broccoli, cauliflower, radishes, kale, and turnips). It also infects mustards. Though misshapen roots are the most dramatic symptom, plant leaves may also wilt too easily during the growing season.

Club root prefers damp, acidic soils like ours here in the Northwest. Its spores live a long time, so crop rotation is not very effective in preventing this disease. Though nearly impossible to eradicate entirely, maintaining a well-drained soil with a pH of 7.2 or above does hinder its growth. If you suspect your garden is infected, take advantage of wintertime to raise the pH of your soil by adding agricultural lime (calcium carbonate) to your beds.

Be sure not to infect other parts of your garden. Don't move soil from an infected area to an unaffected area, and disinfect your garden tools regularly with a mild bleach solution. Don't compost infected plants or leave them in the garden – discard them (roots and all) in your regular household trash.

Copyright © 2004 Brian Ballard. All rights reserved.

Preventing Tomato Late Blight

Until last year, I was innocent of the ways of tomato blights. My effortless introduction to growing tomatoes just the season before had not prepared me for the speed and efficiency of airborne fungi. Surely growing tomatoes was as easy as planting a few indeterminates on flimsy cages and sitting back to wait.

Then early last July, a vigilant gardener spotted late blight on a few tomato plants in a corner of the Interbay P-Patch where I garden. Not since 1998 had our P-Patch dealt with this ravenous killer. Dire warnings of its blitzkrieg-fast, unstoppable spread seemed utterly unbelievable.

The years had lulled us into a sense of complacency. Our tomatoes were left to sprawl and crawl and crowd together in the cool Seattle nights. Surely a few dark smudges half a garden away could not affect my plans for San Marzano sauces, my Seattle Marinaras.

But alas the warnings were true. The Phytophthora infestans fungus that causes late blight thrives in our cool, damp weather and spreads rapidly by airborne spores. It overtook our garden within two weeks. The fungus can also affect potatoes, and was responsible for the infamous Irish potato famine of the late 1840s.

You can identify late blight by looking for dark (almost black) blotches and smudges along stems and leaves. Fruits also begin turning grey or black from the top and harden as they discolor. A different fungus, Alternaria solani, causes early blight, which appears as dark bull's eye leaf spots with lighter, often yellowish halos.

Late blight spores are ever-present in the soil, and once it successfully infects a plant, it's nearly impossible to control in an organic garden. About all you can hope to do is prevent an outbreak. Here are some tips on to help you keep late blight and other tomato fungal diseases from getting a foothold.

• Mulch your soil thickly with leaves or burlap to prevent soil containing spores from splashing onto leaves.


• Leave adequate space between plants for good air circulation. Mature plants should not be allowed to intertwine.


• Keep leaves dry. Apply water directly and gently to the soil, not from overhead. Water in the morning so damp leaves can dry during the day.


• During damp weather, loosely cover your tomatoes with plastic to keep the rain off, but don't wrap them so tightly that condensation forms.


• As your tomatoes grow, begin clipping off the bottom-most leaves to encourage air circulation. Once your tomatoes are about two feet tall, remove all the leaves from the bottom six inches. Keep removing leaves up to about two feet from the ground as the plant grows. Continue to thin out leaves above two feet to encourage air circulation.


• Keep your tomatoes well staked or in sturdy cages. This keeps them up off the ground where soil would be more likely to splash onto leaves.


• In the fall, remove all infected foliage from your garden and dispose of it at home. Do not compost infected plant material.


• Rotate your tomato plantings so you never plant tomatoes or potatoes in the same spot within four to six years. The longer between plantings, the better.


• Don't allow volunteer tomato seedlings to grow. They tend to be weedy and close to the ground, providing easy access to splashed soil.


• Add a bit of lime to your soil. This helps plants remain healthy enough to recover from minor infections, improves fruit formation, and helps prevent blossom-end rot.


• Don't work around wet plants, when you're likely to spread fungus and spores from plant to plant on your clothes.

Copyright © 2006 Brian Ballard. All rights reserved.

Have a Tea Party with Your Veggies!

Here is an interesting way to use your compost in a foliar application: compost tea. Many gardeners swear by its affects in perking up their plants!

What is Compost Tea?

Compost tea is a small amount of compost steeped for a short time in water, much like brewing tea from tea bags. The result is a rich solution containing both beneficial organisms and nutrients that you use when watering or to spray on leaves.

What are the Benefits of Compost Tea?

I originally thought the benefit of compost tea was simply as an organic replacement for water-soluble fertilizers like Miracle Gro or Peter's Plant Food. It turns out that compost tea is actually much more than a mild fertilizer. It also helps inoculate your plants against disease by introducing beneficial bacteria and fungi to the soil or leaves. The process of making compost tea creates an environment where beneficial organisms flourish at the expense of harmful ones.

Bacteria and fungi are very important in the soil, helping roots absorb water and nutrients. These organisms are also important when present on leaves. Spraying plants with compost tea helps control various mildews, molds, blights, and wilt diseases. The theory is that the beneficial organisms compete with the bad ones for food and space. They may even actively kill harmful organisms by eating them or creating natural antibiotics.

How Do I Make Compost Tea?

Compost tea is relatively easy to make from finished compost. Simply fill a 5-gallon bucket about 3/4 full with room temperature, chlorine-free water (either let tap water sit out for a day, use rainwater, or dip some water from a pond or stream.) Then add one shovel-full of fresh compost and stir. You can also use cheesecloth or another loose fabric to hold the compost as you steep it.

Let the mixture sit overnight (stir it occasionally if you're around). When you return, strain the top half of the liquid through a screen or cloth and spray it on plant leaves or water with it. You must use the tea soon after brewing it; otherwise oxygen in the water will be depleted and the beneficial organisms will die or go dormant.

Oxygen-loving (or aerobic) bacteria and fungi are generally helpful. Anaerobic organisms (those that can live with no oxygen) are usually not beneficial, can cause disease, and just plain stink! If you can't use your tea within 12-18 hours after starting it, you will need to aerate it to add oxygen. You can do that with an electric sump pump to circulate the liquid, or better yet by pumping in air. You can use a regular aquarium air pump to oxygenate the tea.

If you aerate your tea, you'll get the best results if you use it within 1-3 days. If you need to keep your tea for longer than that, add a cup of un-sulfured molasses (or other sugar source) every few days to make sure there's enough food to satisfy your growing colony of beneficial organisms.

After using your compost tea, add the remaining solids back to your compost pile, or mix it into the soil.

Never use bad-smelling compost tea. That's a sure sign there are too many nasty anaerobic organisms lurking in it. If your tea smells like sewage, aerate it for a day or two until the smell goes away. (However, you can use your tea if it simply smells yeasty. Foam that may form on top of your tea is not bad for your plants either.)

More Reading

Here are some compost tea resources and recipes on the web.

Compost Tea Basics at GardenWeb

Compost Teas for Plant Disease Control at ATTRA

Brewing Compost Tea by Elaine Ingham

Compost Tea at PA EPA

Compost Tea by Doug Green


Copyright © 2003 Brian Ballard. All rights reserved.