When to Start Spraying Peach Trees

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

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

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

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

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

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

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 fruit 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.