Brown Rot on Peaches

All of the rain we are receiving this year is beginning to cause problems with diseases on peaches. Brown rot can be a devastating disease on peaches and can quickly spread to all of the fruit on the tree. The picture shows brown rot developing on fruit that has just recently dropped.

In order to prevent brown rot from consuming all of your peaches, a fungicide will need to be applied on a weekly basis beginning approximately 4 weeks preharvest. If rainfall is heavy during this time then the interval should be shortened even further. Also if sulfur is being used the interval should be shortened. Removing infected fruit will also help reduce inoculum.

Training Fruit Trees

As soon as trees are planted training should begin to get the shape you want. Commercial growers usually get whips and then head them back to whatever point they want their first limbs to start. Many fruit trees have a very upright growth habit (Picture 1). The narrow crotch angles caused by this upright growth results in a weak limb and will usually break under a crop load.

In order to prevent narrow crotch angles the limbs should be spread as soon as possible. Spreading can be accomplished by placing a clothes pin just above the limb so that it is almost horizontal (Picture 2). The plastic clothes pins are recommended since they are more durable. Limbs can also be spread by propping a toothpick between the limb and trunk.

Notice that I did not spread the top limb. This will be a central leader tree and that limb will eventually become my main trunk. You need to eliminate any limbs that will not become part of your eventual structure.

Peach Twins

I am seeing more peach twins, or doubling, then I have in past years. The picture shows a typical peach twin. Peach twins are formed the previous year as the result of hot, dry conditions. The amount of twins is not worth worrying about since the represent a small percentage of fruit on the tree. These fruit are pretty much worthless and should be removed during the thinning process. Irrigation during dry summer weather will help reduce twins for the next season.

June Beetles and Peach Brown Rot

As peaches begin to ripen they are prone to have insect and disease problems. In particular, june beetles and brown rot can destroy most of the fruit on the tree. June beetles are attracted to ripening fruit and will congregate in large enough numbers to completely consume the fruit. The picture shows not only june beetles but wasps and hornets feeding on ripe fruit.

The feeding injuries are prime sites for brown rot infections. Brown rot develops quickly on the fruit and can also spread quickly to other fruit on the tree. The peach shown in the bottom picture has brown rot on over 50% of its surface and is beyond salvaging.

In order to protect fruit from insects and diseases, peaches should be sprayed on a weekly basis beginning 4 weeks before anticipated harvest. Some stores carry a product that already has the insecticide and fungicide mixed together. Make sure you get thorough coverage to prevent brown rot from becoming established.

Cicada Damage to Fruit Trees

Now that the cicadas have all but died off, we are starting to see the damage they can do. The sawing action by the female, when she lays her eggs, severely weakens the twigs. These twigs snap off very easily in any kind of wind or with a fruit load.

There is not much you can do now except prune out the broke branches. Young trees may have to be retrained in order to get them back to the way they should be. In extreme instances you might have to start all over on newly planted trees and head the tree back.

Weak Peach Trees

In many of the commercial peach orchards this year we are seeing trees that look very weak. The limb on top is normal growth while the limb on bottom looks stunted. There is some concern that these trees may not be able to ripen the crop and some trees may die.

There are a couple of explanations for the weak appearance. First, the trees have set a tremendous crop and are shifting most of their energy in maintaining the fruit. Second, due to the extremely dry weather last year, the root system of the tree may not have been able to grow during the fall and the tree is operating on a smaller root system. A combination of these two factors may also be causing the problem.

Some growers are tempted to put out more nitrogen in order to perk the trees up. However this may cause more problems by spurring the tree to put on excessive growth, resulting in excessive vigor and poor fruit quality. You might also consider the high price of fertilizer when making the decision.

Instead of adding more fertilizer, you might want to consider thinning the excessive fruit off as quickly as possible. The longer the fruit stays on the tree the more it puts a drain on the trees resources. Give the tree a couple of weeks after thinning to see how it responds, and if a light fertilizer application is needed.

May or June Drop in Peaches

In our area of the state, peach trees have set a very large fruit load. In one of my earlier posts I discussed the need for thinning to reduce the stress on the tree and to create larger fruit. The tree will also take some measures on its own to reduce the crop load.

When the tree starts to drop fruit in the spring of the year it is often called May drop or June drop, depending on where you live. The dropped fruit usually were not pollinated, and therefore do not have a viable embryo. Pollinated peaches will normally be much larger then the fruit that was not pollinated. Another way to tell is to cut the fruit open and look at the embryo. The picture shows a pollinated fruit on the left and a peach without an embryo on the right.

Some people will wait until after May/June drop to see how many fruit are left to thin off. This strategy may work, in some years where you might not think that you have a full crop left. Remember, the earlier you thin the greater fruit growth response you will get, so do not wait too long.