Peach Leaf Curl

Tuesday, December 14th, 2010 by Jenny Watts
    • Liquidambar and Japanese maple trees can’t be beat for fall color. Choose them now while you can see their bright colors.
    • Tree collards are delicious winter vegetables.
    • Rake and destroy leaves from fruit trees that were diseased this year.
    • Tie red raspberry canes to wires; prune to 1 foot above the top wire or wrap the canes around the top wire.
    • There’s still time to plant spring-flowering bulbs, but don’t delay. Daffodils, tulips and hyacinths are still available.

Protect Peaches from Peach Leaf Curl

Probably the most irritating thing about seeing the characteristic warty red leaves of peach leaf curl is realizing that it’s already too late to do anything about the disease.

Peach and nectarine trees generally grow quite well here, but many varieties are prone to a disease called peach leaf curl. When the tree leafs out in the spring, infected leaves quickly become blistered and distorted and turn yellow to reddish in color. Gradually these leaves drop from the tree and are replaced by a new crop of usually healthy leaves.

The production of two sets of leaves decreases the energy the tree can put into new growth and fruit production. If leaf curl is uncontrolled for several years, the tree will decline and need to be removed.

The fungus spores of peach leaf curl live over the winter in microscopic crevices on the tree and are ready to infect young leaves just as the leaf tips are exposed in the spring. Peach leaf curl is worst when we have wet spring weather, so it is always good to apply a preventative spray.

Timing of dormant sprays is very important. In northern California, apply a first spray about November 15, or when at least 90% of the leaves have fallen. The most effective spray for the home orchardist is a fixed copper fungicide, which comes in a powdered form.

A second application should be made in late December or January. The third, and very important spraying should be made just before the buds swell, usually in mid-February.

Full coverage of the tree is essential. Leaves developing from buds that are not covered by fungicide will probably become infected. For maximum control of peach leaf curl, spray trees thoroughly with a copper fungicide three times during the winter.

If you do not already have peaches in your orchard, you might consider planting the newer, curl-resistant varieties. ‘Frost’ peach and ‘Q-1-8 White’ peach are both highly resistant and ‘Indian Free’ peach is also very resistant.

Peach trees are worth growing in this area even if you do not get a crop every year. In a good year, a single tree may give you 200 pounds of luscious, juicy fruit. Take care of your peach and nectarine trees and look forward to bountiful, healthy crops of delicious, home-grown fruit.

Watch Out for Plant Diseases

Wednesday, 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.