Crown rot is a disease caused by the fungus Phytophthora infestans which attacks the roots of most types of plants. This infection causes plant death with white lesions appearing on the leaves.
The symptoms are usually not visible until after several years have passed, but they include wilting or browning of foliage, loss of stems and branches, stunted growth and sometimes even death.
Symptoms of crown rot on African violets (Viola spp.) are similar to those of other susceptible plants such as sunflowers, but may take longer to appear. Most often the first signs are small white spots on the leaves, followed by yellowing and eventually browning.
Other symptoms include wilting and failure to thrive.
African violets are among the most common plants affected by crown rot. They grow best when kept cool and moist, so care must be taken to prevent them from getting too warm or drying out. If left outside during hot weather, they will die back before their leaves turn yellow.
When grown indoors in containers, they need to receive at least 12 hours of direct sunlight each day to avoid leaf burn.
Virtually any plant can be affected by crown rot, but some are more susceptible than others. Tomatoes (Lycopersicon esculentum) and strawberries (Fragaria spp.) are particularly easy to kill with this disease.
It usually appears as a light to dark brown crusty growth on the roots, but these fungal colonies may also exist completely inside the soil without producing any noticeable exterior symptoms.
When root rot occurs, the leaves usually wilt and turn yellow, growing progressively smaller as time goes on. In the case of crown rot, however, it may take months or even years for a plant to show any external symptoms. This makes it difficult to tell whether the problem is blight, root rot or a combination of the two.
There are two types of crown rot: blossom end rot and stem waste. Blossom end rot occurs when the plant fails to absorb enough calcium, leading to brown or black spots near the bottom of the fruit in tomatoes. If the problem occurs near the stem, it is called stem waste.
This makes the fruit inedible regardless of where it is on the tomato. Blossom end rot and stem waste can be prevented by making sure the soil is moist but well drained, adding dolomite to the soil or planting tomatoes in a container filled with gravel.
There are several preventative measures you can take when trying to grow african violets in containers. Keep your container plants indoors in a sunny location during the winter months. Check the plants periodically for any sign of rot, wilting or discoloration of foliage.
While this is most common during the winter, it can happen at any time. Make sure the soil is well-drained and allowed to dry out before re-watering. If you see black spots on the leaves or yellowing, wilting or browning, remove affected foliage and destroy it to prevent the fungus from spreading.
When crown rot occurs, affected plants must be immediately removed from the garden or container so as not to infect other plants. Any tools used during harvest should be thoroughly washed with a strong disinfectant or bleach to prevent spreading the fungus. Even a small amount of rot can quickly spread to an entire garden, so it is very important to take immediate action!
Also Known As: Blossom end rot and stem waste, both types of crown rot, are also known collectively as black root rot.
Prevention: Crown rot can be prevented by providing well-drained, porous soil and making sure it doesn’t stay wet for long periods of time. Fungicides are of little use since they are not absorbed into the plant in a useful manner. It is best to prevent this problem rather than cure it!
Solutions: If crown rot has already set in, it can take months for a plant to show signs of recovery. Some people have had luck by cutting away the rotten portion of the stem and digging out all of the infected soil. It is best to replant the area in something other than edible crops for at least one full growing season.
If you’ve had this problem for several years in a row, it might be best to dig up and discard the entire bed. Crown rot can be extremely difficult to get rid of!
Also Known As: Blossom drop is the term used to signify that a flower has prematurely fallen off before it could produce a fruit.
Prevention: There is really no way to prevent blossom drop from happening, as it is common to all varieties of tomatoes. The best thing to do is to be aware that it may occur and not take it personally!
Solutions: Blossom drop usually occurs due to over-pollination or unfavorable weather conditions during flowering. It hardly ever affects more than 5 – 10% of the blossoms. Another possible solution is to hand-pollinate in an attempt to increase the size of individual fruits.
The weight of the larger fruit may be enough to keep them on the vine. This may not seem like a viable solution, but if you’re growing giant varieties of tomatoes it just might help.
Also Known As: Blight is a fungal disease that is very widespread and attacks a wide variety of plants, not just tomatoes.
Prevention: Keep your garden clean! Remove and destroy all infected plants, as this is the best way to get rid of the fungus. Also, avoid planting tomatoes where peppers, potatoes or eggplants have grown in the last three years.
Choose a well-drained part of the garden for your tomatoes and don’t over water them.
Solutions: If you discover that your tomatoes have gotten blight, there isn’t much you can do except to quickly remove and destroy the infected plants. The quickest way of spreading the disease is to move infected plant parts (even leaves) from one area of the garden to another. This is why it is so important to keep your garden clean and free of old plants.
Once the fungus takes hold in your garden, it can spread very quickly.
Also Known As: Corn earworm is a type of moth whose larvae (caterpillar) feeds on various types of plants, including tomatoes. It gets its name from its favorite food of corn, but it has also been known to feed on tomatoes when available.
Prevention: Hand pick off and destroy any caterpillars you see on your tomato plants. Also, grow some “trap”
Sources & references used in this article:
Insects, Pests and Diseases of the African Violet Family: How to get rid of your bugs and diseases on your African violets plants. by N Robitaille – 2005 – books.google.com
Crown and root rot of African violets (Saintpaulia ionantha) caused by Phytophthora nicotianae var. parasitica in Brazil. by TMW de Souza, E Feichtenberger… – Summa …, 1991 – cabdirect.org
Growing African Violets by CC Fischer – 1978 – ecommons.cornell.edu
You Can Grow African Violets: The Official Guide Authorized by the African Violet Society of America, Inc. by J Stork, K Stork – 2007 – books.google.com
African violets by JR Culbert, D Hickman – Circular; 942, 1966 – ideals.illinois.edu
Houseplants: Proper Care and Management of Pest Problems by JJ Knodel, K Kinzer, R Smith – 2009 – library.ndsu.edu