Container Gardening Complete

Job:06-700309 Title: CPS - Container Gardening Complete

700309 - ContainerGardens_001-272_FINAL.indd 204 5/24/17 12:20 PM
Job:06-700309 Title: CPS - Container Gardening Complete
Job:06-700309 Title: CPS - Container Gardening Complete

700309 - ContainerGardens_001-272_FINAL.indd 205 5/24/17 12:20 PM

204 chapter 4

Early Blight (Alternaria solani)

Description: This common fungus first appears

as irregularly shaped, bulls-eyed brown spots on

infected plants. Often, the leaf tissue around the

spot turns yellow. Early blight always appears first

on the lower leaves of the plant. If left untreated,

the leaves turn yellow, develop dark irregular

splotches of infected tissue, and fall off, but the

fruit will continue to ripen. In severe cases, the

fruit can also be affected.

Plants affected: Tomatoes, potatoes, eggplants,

and peppers.

Solution: The pathogen lives in the soil, and once a

garden has shown signs of the early blight fungus,

it’s there to stay because the organism easily

overwinters in the soil. However, for container

gardeners, early blight is far less problematic.

Be sure to wash empty containers with a 10%

bleach solution at the end of the year to prevent

spores from spreading via infected plant debris.

Fortunately, most tomatoes will continue to

produce even with moderately severe cases of early

blight. Organic fungicides based on Bacillus subtilis,

potassium bicarbonate, or copper are effective in

preventing and managing this disease.

Late Blight

(Phytophthora infestans)

Description: Late blight is one of the most

destructive diseases of tomatoes and potatoes,

but it’s not very common, particularly in the

north where it doesn’t survive the winter without

a host plant. This pathogen causes irregularly

shaped splotches that are slimy and water-

soaked. They often occur on the top-most leaves

and stems first. Eventually, the spots merge

together and cause entire leaves to rot on the

vine. There may also be masses of white spores

on the leaf undersides, as well. In northern

regions, this organism can only overwinter on

infected potato tubers that survive underground.

In the south, however, where freezing

temperatures don’t occur, it easily survives the

winter. Come spring, the spores are readily blown

north where cool, wet, spring weather conditions

can cause it to thrive.

Early blight is a common fungal disease. It starts as

bull’s-eye-shaped spots that quickly progress to leaf

shriveling and drop. The bottom leaves are always

aected first.

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Troubleshooting 205

Plants affected: Tomatoes and potatoes.

Solution: The spores of this disease are fast-

spreading, moving on the wind for miles. Planting

only locally grown plants can help keep the

pathogen out of your area. Once late blight strikes,

there is little a gardener can do except tear up

the plants, put them in a garbage bag, and throw

them out to keep the disease from spreading.

Organic fungicides based on Bacillus subtilis are

somewhat effective.

Southern Bacterial Wilt

(Ralstonia solanacearum)

Description: Plants infected by this bacterial

disease are in big trouble. Though it is naturally

found only in tropical regions and greenhouses,

the disease often arrives to the garden via

purchased plants grown in places where the

disease is present. It is soilborne but can be

transmitted by soil, water, plant matter, and

even on clothes and tools. Initially only one

or two leaves may wilt during the day, while

the remaining leaves appear healthy. As the

infection spreads, more leaves wilt and yellow

until the entire plant succumbs, despite the stem

remaining upright. Lower stems may develop dark

brown splotches. Slimy, viscous ooze comes out

of the stems when they are cut. When cut stems

are placed in water, milky streams of bacteria are

seen streaming out of the cut.

Plants affected: Southern wilt affects almost 200

different species of plants. In North America,

it attacks geraniums, impatiens, mums, zinnia,

salvia, petunias, eggplants, verbenas, and many

other bedding and vegetable plants.

Solution: Bacterial wilt is soilborne and can

survive for long periods in the soil on roots and

plant debris. Like many other diseases, it favors

high temperatures and high humidity. Sadly,

there is no cure for this disease. Once confirmed,

infected plants must be removed and discarded in

the garbage. Keep them out of the compost pile.

Late blight is a devastatingly fatal disease that

thankfully doesn’t strike often. It aects tomatoes

and potatoes.

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