Watch Out for Plant Diseases
May 26th, 2010 by Jenny Watts- • Tomatoes are the most popular summer vegetable. Choose from the many varieties available now so you can enjoy delicious home-grown flavor.
- • Petunias can be planted now. Their bright flowers will bloom all summer in hot, sunny locations and they will take a light frost.
- • Plant an herb garden in a container near the kitchen door for convenient fresh spices like basil, oregano, parsley and thyme.
- • When you plant your vegetable garden, why not grow a little extra to donate to the food bank this summer.
A Year for Plant Diseases
Any plant can be attacked by disease organisms. During wet spring weather, plant diseases are very common. Bacterial infections, fungi and viruses may be attacking some of your plants, so keep a sharp eye out for problems.
If soil is waterlogged, plant roots may deteriorate rapidly, largely due to the lack of oxygen in the soil. Waterlogged soil also favors the development of diseases such as damping-off and root rot fungi. Stems of annual and perennial flowers and vegetables, may darken and get soft, causing the plants to die. There is no cure for this problem.
Leaf diseases can be due to either fungi or bacteria. Powdery mildew, fungal leaf spots, and rusts are fungi which are spread by rain. You can’t remove the problem from the leaves it is on, but you can protect new growth and uninfected leaves by spraying with a preventative spray. Neem oil is a non-toxic spray that has proven to be quite effective.
Peach leaf curl is a fungus that infects the leaves before they open in the spring. The puckered and blistered leaves turn bright red with a white powdery layer over the leaf surface. Affected leaves will drop prematurely and a second set of leaves will come out that are usually not affected. Preventative spraying must be done during the dormant season and in severely wet springs, such as this, it may not be very effective. Remove the curled leaves, preferably before the white powdery spore layer develops, and dispose of them.
Bacterial leaf spots are very common in wet weather. These black or dead patches may be surrounded by a yellow margin. Usually when the weather dries out, the new growth will be unaffected, but it is a good idea to remove infected leaves and clean up dead leaves under the plant.
Bacterial canker often affects plum and cherry trees. Typically, a tree will push out new growth in a normal manner, then suddenly the leaves wither and die. The plants cannot pull up moisture into the leaves because the canker has girdled the trunk or branch of the tree. There is not much you can do about this condition, except prune out affected branches in the summer.
Viruses can also affect plants. Many viruses do not harm plants, such as those that cause variegation on leaves or flowers. But some can distort leaves or fruits, and the only control for these is to destroy infected plants and wash hands and tools so that you do not spread the problem to other plants.
If you see a disease problem that you need help with, pick several leaves in different stages of development, seal them in a plastic bag, and take them to your local nursery for identification and help. You may find some unusual plant problems in the garden this year.