Fruit Tree Update

Brown Rot on Peaches

2009-06-17T05:40:00.000-07:00

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

2009-05-28T05:21:00.000-07:00

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

2009-04-21T07:12:00.000-07:00

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

2008-07-23T11:25:00.000-07:00

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

2008-06-17T11:50:00.000-07:00

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

2008-05-08T11:14:00.000-07:00

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

2008-05-08T07:59:00.000-07:00

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.

When to Start Spraying Peach Trees

2008-04-22T11:12:00.000-07:00

Peach trees suffer from a wide variety of insect and disease pests. Commercial growers will begin spraying during bloom to control the disease blossom blight. Since this disease is only an occasional problem, I normally recommend that homeowners wait until after all of the flowers petals have dropped off the tree.

My first recommended spray begins at what is called shuck split or shuck off. This is when the sepal that used to hold the flowers splits or just falls off (picture). A fungicide is recommended at this time to control the disease scab.

In the spring, peaches should be sprayed at least 2 times, about 2 weeks apart with a fungicide. After that scab should no longer be a problem. You might be able to avoid spraying during the rest of the summer until 4 weeks preharvest, when brown rot sprays will be needed (covered in a later post).

Both organic and conventional pesticides are available for scab control. Wettable sulfur has been successfully used for years, although the interval between sprays may need to be shortened to 7 to 10 days. Three sprays instead of 2 will be needed for sulfur. Captan is a good conventional fungicide, but you may have to go to a farm and garden shop to find it. Scab picture by Dave Rosenberger, Cornell University

Recognizing Cold Damage to Peach Blossoms

2008-04-03T12:06:00.000-07:00

Spring can be a very dangerous time for fruit tree blooms. If cold weather hits when the buds start to swell and bloom then some or all of the blossoms can be killed. Generally it takes temperatures below 28 degrees Fahrenheit to damage blooms, but a great deal of variables may come into play - such as how long the temperature stays below freezing.

Once the bloom is killed the it may take some time to recognize the damage. You may be able to see the damage the next day if temperatures rise significantly. The easiest way to tell if the bloom is still viable or not is to look for the pistil in the center of the flower. In the picture the petals,anthers, and calyx have been removed. If the pistil is nice and green (bloom on the right) then it survived the weather. If the pistil is turning brown or has a water soaked appearance (bloom on the left) then the bloom is dead and should drop off within a couple of weeks.

In a normal year, you can loose up to 90% of the blooms and still have a good crop of peaches. Bloom thinning due to cold weather can also save you some time later on in the season when it is time to thin some of the fruit off. Unfortunately, thinning due to cold is not very selective, which means you may have fruit on some twigs and none on others.

Limb Spreading Revisited

2008-02-05T07:20:00.000-08:00

In a previous post I talked about the need to spread tree fruit limbs (particularly apples and pears). I mentioned the reasons for limb spreading which included increased branching. I have taken some pictures that illustrate this point very well.

In the first picture you seed a limb that is growing very upright. In fact, it is growing so upright that it is beginning to compete with the main trunk of the tree. You will notice that the bottom two-thirds of the limb has little to no branching, which is due to the upright growth. A limb like this will produce very little fruit with almost all of it on the end of the limb.

This photo shows a limb that has been properly spread. Notice the branching up and down the length of the limb. The increased branching means increased fruiting wood and more fruit production.

The upright limb will be spread over the next couple of weeks and by mid summer we should see a big difference in the way it looks.

Sanitation Around Fruit Trees

2008-01-11T10:35:00.000-08:00

Many diseases, and some insects, that attack fruit trees during the summer will overwinter on or under the tree. Fruit that is left on the tree or allowed to rot under the tree often carry fungi that will affect next seasons crop. Even leaves left under the tree can be a source of diseases the next growing season.

Often times fruit left on or around the tree will not rot completely. These fruit will shrivel up into a small ball and are called mummies. Although they may look dry and harmless these mummies will produce fungal spores during the spring and summer that can infect new fruit. Brown rot on peaches and summer rots on apples can quickly spread and may be uncontrollable, even with fungicide applications.

The same is true for leaves left around the tree. In previous posts I have mentioned a disease called scab on apples. This fungus will invade leaf tissue and fruit which may cause defoliation and substandard fruit. Leaves on the ground near the tree are a primary source of scab spores during the spring of the year.

Cleaning up the mummies and old leaves will greatly reduce the source of these fungi and help in disease control. Old fruit should be removed from the area and destroyed. Old leaves can either be removed or shredded by mowing to hasten leaf decomposition. Either way, sanitation is an important step in managing diseases for the upcoming season.

Weed Control Around Fruit Trees

2007-11-13T11:39:00.000-08:00

Now that fruit trees are going dormant you may think that there are no tree fruit chores to be done right now. However, if you have grasses and weeds around the tree you might want to consider a little vegetation management. Even though the weeds are not competing with the tree during the winter for water and nutrients, there are advantages to having bare ground under the tree.

One of the biggest advantages of bare ground is vole control. Voles are mouse like animals with short tails and small ears. Pine voles are subterranean, but are different from moles in that they do not push up the soil when they tunnel. Instead the ground feels spongy, especially if you have a large population.

Pine voles can be very destructive in that they will strip off all of the bark on the trunk below the soil line (top picture). The next season, the tree may leaf out alright, but slowly decline as the season progresses (bottom picture). This girdling will eventually kill the tree. Having bear ground exposes the tunnel to natural predators, like snakes, foxes, dogs, and cats. Voles also love mulch, so you may want to pull the mulch back to check for the vole activity.

Another advantage of having bare ground is frost protection in the spring. Studies have shown that bare, wet ground absorbs more heat then soil covered with weeds or mulch. This soil releases the heat at night and can raise the temperature in the tree by a couple of degrees (not much, but a couple of degrees can mean the difference between having fruit and having no crop).

Don't Fall Prune Fruit Trees

2007-10-24T10:15:00.001-07:00

I will talk about pruning fruit trees in a later post, but I would like to emphasize that now (fall) is not a good time to prune fruit trees - for 2 main reasons. The first reason is that trees are shifting nutrients away from the top of the tree to the root system. By pruning now, you may be limiting the amount of nutrients that are available to the tree next spring (when it really needs it). Waiting until the tree has gone completely dormant will insure that the maximum amount of nutrients have been stored.

The second reason you do not want to prune now is shown by the picture. In this image, you can see new growth emerging as a result of recent pruning. This new growth is very tender and very susceptible to frost and freeze damage (if we ever get any cold weather). Chances are this new growth will not harden off in time before winter sets in and will be killed.

Fruit trees, in this area, are already under stress from dry conditions. Adding stress to the tree by fall pruning may reduce next years crop and reduce viable fruiting wood.

Sooty Blotch and Fly Speck Removal

2007-08-29T06:22:00.000-07:00

In a previous post I mentioned some of the diseases that attack apples. Rots can be cut out, but most of the time the summer rots will make the fruit useless. Sooty blotch and fly speck grow on the surface of the fruit and, therefore, can be removed without affecting the f ruit much.

One of the methods that commercial growers might use is to soak infected apples in a chlorine solution. After soaking the apples, the fruit is them brushed to remove any residue. These pictures show a before and after image of apples that were treated with a chlorine solution. The amount of chlorine used will depend on the formulation and concentration of the product. You should be aware if you use a product such as Chlorox, that you may be in violation of pesticide laws. Also you may leave unwanted residue on the fruit.

The safest way to remove sooty blotch and fly speck is to simple peal the fruit. In some circumstances, the diseases can be rubbed off with water and a cloth. In either situation, the flesh of the fruit should be fine.

Common Diseases of Apples

2007-07-18T05:49:00.000-07:00

Apples, like many other tree fruits, have a number of diseases that infect both leaves and fruit. The picture to the right shows some of the different diseases - the apple on the right has scab, the apple in the middle has sooty blotch/fly speck (blotches and specks on the top of the apple), and the apple on the left has a summer rot (bitter rot). In order to control these diseases, you should understand the life cycles.

Scab is primarily a spring disease. The fungus overwinters on infected leaves on the orchard floor. In the spring, spores are released from the leaves and spread by wind to infect newly emerged apple leaves. As spring progresses more spores will be produced by the newly infected leaves which will infect more leaves and fruit. A tree with a serious scab infection can be defoliated and the fruit will be ruined.

The easiest way to control scab is to plant disease resistant trees like Pristine, Enterprise, Goldrush and Liberty, to name a few. If you have trees that are susceptible to the fungus then the tree must be sprayed on a regular basis when the new leaves emerge in the spring, particularly during a wet spring. Removing or destroying leaves on the ground during the winter will also reduce the disease inoculum.

Summer rots develop much later in the season when temperatures start to rise. There are a number of different summer rots (black rot, white rot, bitter rot) and certain varieties may be more susceptible then others. The only way to control summer rots is to spray a fungicide on a regular basis (every 10 days to 2 weeks depending on rainfall).

Sooty blotch and fly speck are also diseases that build up in hot weather. Sooty blotch is just like the name says and forms sooty patches all over the fruit. Fly speck forms little, black specks on the fruit. Both of these diseases are superficial on the fruit and the damage is only cosmetic. Most fungicide sprays that control summer rots will also control sooty blotch and fly speck.

Pest Alert for Commercial Growers

2007-07-11T05:12:00.000-07:00

Codling moth trap catches have dropped off to less then 5/trap in 3 out of the 4 monitored orchards. The 4th orchard is next to an abandoned orchard and has a history of high trap counts. It looks as though we are through with the 2nd generation codling moth emergence. Treatment for the 3rd generation emergence should occur at 2250 degree days, which should occur in early August if weather conditions remain the same.

I have been finding some leaf damage in all of the orchards that I have been scouting. The picture to the right shows a crinkled leaf on top, and what looks like leaf miner mines on the bottom. Dr. Turner Sutton has examined photos of the leaves and says it is classic symptoms of freeze injury. These leaves may turn yellow and drop off, but the good news is the condition will not get worse. The number of leaves that are affected is a relatively small percentage per tree.

Disease pressure still remains low at this time, even in unsprayed blocks.

Limb Spreading on Apple Trees

2007-07-10T05:48:00.000-07:00

Depending on the apple variety, many apple trees will have a very upright growth habit. This tree shows the typical growth pattern. The problem with upright growth is that the limbs form a narrow, weak attachment to the trunk. Limbs with narrow angles can easily break under the weight of a fruit load. Also, the upright growth forms a dense tree canopy which prevents sunlight penetration and reduces air movement in the tree. In addition, limbs need to be spread in order to get fruiting wood established along the entire length of the limb instead of just at the tip.

To improve limb angles the individual limbs must be spread manually. Spreading is best done when the twigs are relatively new. The object is to get the limb angle going into the trunk as close to 90 degrees as possible. The top limb on the left shows the proper limb angle.

Limbs can be spread using a variety of techniques. For new growth that is less then 6 inches long, a toothpick can be inserted between the limb and trunk to get the proper angle. For larger limbs, tree spreaders can be used just like the toothpicks. In the top photo you can see a commercially produced limb spreader being used. Anything can be used to spread the limbs as long as it is strong enough to hold the limb open. In the bottom photo, a string is used to tie down the limb. Make sure if you use string, do not to tie it too tightly to the limb as this will girdle the limb as it grows.

Spreaders do not have to be in the tree permanently. In fact, after about 4 to 6 weeks the spreaders can be removed and the limb should stay at the proper angle. Spreading is a continuous process that must be done every year to insure proper tree structure.

Orchard Pest Status - July 3

2007-07-03T05:03:00.000-07:00

Codling moth trap counts are averaging 12 per trap and the degree day model is at approximately 1500 dd. The moths should be about at the end of the 2nd generation emergence. Third generation codling moth emergence should begin about 1900 degree days which will be in about the end of July, depending on weather conditions. Dr. Walgenbach does stress that if trap counts remain high in your orchard then additional insecticide applications may be necessary.

Japanese beetles have been showing up for a couple of weeks now. Sevin is probably the most effective, and least expensive, insecticides available. Other insecticides will work so check the apple spray manual for recommendations.

I am seeing other minor insect activity but nothing to be concerned about. Diseases are also very low in orchards that are being sprayed.

Thinning Fruit Trees

2007-07-02T12:40:00.000-07:00

In a normal year many peach, apple, and other fruit trees will set more fruit then the tree can handle. Too much fruit on the tree will cause the fruit to be smaller and can also break limbs from the weight. In order to get adequate size some, if not most, of the fruit will need to be removed - a process called thinning.

The top photograph shows how fruit typically clusters on a limb. You may also notice some of the fruit has some type of damage. Start off by removing the damaged and small fruit. Next remove enough fruit so that there are about 6 inches between fruit. The picture on the bottom shows how the fruit should look after thinning.

The earlier that fruit is thinned the better the size response of the remaining fruit. You may want to wait until after some of the unpollinated fruit drop off naturally (usually in May or June). You do not have to dispose of the fruit that is on the ground since they usually decay very rapidly.

Pest Alert for Commercial Growers

2007-06-28T05:15:00.000-07:00

Codling moth trap catches in the Brushy Mtn. area of North Carolina are on the rise. Average trap counts are at 27/trap and the degree day model is at 1300 on June 25. The high trap counts signal the beginning of the emergence of second generation codling moths. Those growers with a history of moderate to high codling moth pressure should consider applying 2 insecticide applications approximately 14 days apart.

European red mites are showing up in a few area orchards, particularly in those orchards that have had a pyrethroid applied this season. Treatments are recommended in orchards with over 5 to 10 mites/leaf. High mite populations can lead to defoliation, especially in those varieties that are susceptible to alternaria blotch.

Spotted tentiform leaf miners are also showing up at this time. From the leaves that I have examined, almost 30% of the larvae have been parasitized so no treatments are recommended for this pest. In past years, the parasite has controlled STLM at satisfactory levels.

Few diseases are showing up at this time (probably due to dry weather).

Summer Pruning Peach Trees

2007-06-27T11:51:00.000-07:00

Healthy apple and peach trees normally put on a large amount of new growth during the season. It is not unusual for peach trees to grow 6 feet or more in a season. In a freeze out year, like this one, tree growth can become even more unmanageable with no fruit on the tree.

The large sprouts growing up in the middle of the tree are called water sprouts, which are not very beneficial to the tree. Water sprouts will shade out lower branches, causing twig death. Too much shading will lead to increased twig death and result in lowering the crop production potential of the tree.

In order to prevent over shading, a certain amount of summer pruning should be performed. Summer pruning does not require any pruners when done at the right time of the season. Growth should be 12 to 18 inches long, or shorter and the wood should be a light green color.

Summer pruning should concentrate on the vigorous upright growth in the center of the tree. More detailed pruning should be done in the late winter or earl spring.

Water sprouts can be removed my grasping the twig and ripping it in a sideways motion to the branch. This type of pulling action will help prevent pulling bark off of the branch and causing injury to the tree. Pulling sprouts parallel with the branch will, often, end up stripping bark from the tree. Don't be afraid to take out sprouts, thinking that you are going to hurt the tree. Actually you are doing the tree a favor by opening up the tree to sunlight penetration.

If you look closely at the pictures below (before - top, after - bottom) you will see that the lower parts of the "after" tree are much lighter even though it does not look like much wood had been removed.

As mentioned before, failure to summer prune will end up killing many of the trees lower branches. The peach tree below shows virtually no fruiting wood on the lower half of the tree. Another added benefit of summer pruning is that some of the vigor will be taken out of the tree by reducing the number of leaves on the tree

The Beginning

2007-06-27T06:51:00.000-07:00

This blog has been set up to help homeowners, amateur growers, master gardeners and even commercial growers deal with the day to day tasks of taking care of fruit trees - particularly peaches, nectarines, and apples. I hope to have useful information as the season progresses, but for now, at least it is a beginning.