Xtremehorticulture

Xtremehorticulture of the Desert

Fireblight Causes Problems with Fruit Trees if Missed Earlier

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 Q. I came back from vacation and my ‘Gala’ apple tree branch was dead.  The tree also has some black spotting under the bark. I’m hoping it’s not damage from fire blight.  Both pictures are fire blight in ‘Gala’ apple tree with an older infection. As this reader suggested, the earlier symptoms were not noticed and the bacterial disease has now invaded the trunk. Most likely the trees will either die or may serve as a host for further infection of trees.  A.  I looked at the picture you sent of your fruit tree, and it looks like older fire blight disease that escaped earlier detection and is now in the trunk of your tree. Fire blight is a serious disease that is highly contagious for many apples. It’s more damaging to some apples like ‘Pink Lady’ than others such as your ‘Gala’.  It’s particularly damaging to all Asian pears.  It can be damaging to some European pears, like ‘Bartlett’ and others, such as ‘Keiffer’, it doesn’t seem to affect much here. This is fire blight disease on a recently planted ‘Bartlett’ pear. Sometimes this disease can come in on nursery plants from “dirty” growers. It is damaging to some ornamentals like pyracantha and some cotoneasters in the rose family. The varieties of these plants may show differences. It just depends on the genetics of the plant combined with the genetics of the disease. When I saw this disease in the spring it was heavily into Asian pears, some European pears and many apples and quince. What gave it away then was the early spring growth, which was black, hooked and had the presence of sap. Fire Blight control is normally through removal of the infected limbs 10 to 12 inches below where the infection is seen. What gave it away to me now are the dark cankers (black spotting) on the trunks of your trees and also the presence of sap.  The “sap” is what is contagious and can cause it to spread.  The dark cankers are probably from earlier fireblight infestations. Once this particular disease gets into the trunk the tree usually dies. If the tree continues to look bad or worsens, I would cut these trees down and get the pruning off of the property. You cannot use this wood for wood chips or anything near plants or it can reinfest susceptible plants.

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Possible Fireblight Again

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  Although not confirmed this is what fireblight disease can look like on pear. Dead or dying branches can appear in April or May. Ah, Yes the Memories Do you remember the outbreak of fireblight disease about 10 years ago? Fireblight disease can be brutal to many of the landscape and Orchard trees in the Apple family (pome fruit) in an orchard if it’s not caught right away. The hardest hit trees were Asian pear (Hosui, Shinseki, 20th Century and many others) then the next hardest hit were many of the European pears (Bartlett in particular) and a few apples such as Mutsu and Pink Lady. This disease is extremely virulent. Please check in the landscape Pyracantha, loquat, cotoneaster, Photinia, flowering ornamental pear such as the Callery types.   Fireblight disease may not be this obvious to the casual onlooker. How Does It Spread? This deadly bacterial disease to plants is spread from plant to plant in the spring when the flowers are open or through open wounds after late pruning. However, this disease is frequently not easily seen until April or May.  This picture is the common description of fireblight disease; black like it was hit with fire and the prominent Shepard’s hook.  How to Control It Just because this disease seems to be in remission, don’t trust it. It will be back like gangbusters. Prune out the dead wood 12 inches below where the infection seems to be active. When you’re done making the cut, sanitize your pruning blades within 70% solution of isopropyl alcohol. Do this after every pruning cut. Then when you have all of your cuttings together, bag them, tie the bag shut and put it in the dumpster far away from the infected plants. Wash your hands, your tools and treat them with a isopropyl alcohol I last time before you put them away. This disease was tweeted by me. So if you don’t subscribe to my twitter account, get it!  Robert Ll Morris @Extremehort Update: Fireblight disease is still popping up in May on fire blight pruned Asian pears and their hybrids, many European pears like Bartlett, some apples, quince, ornamental pear, pyracantha and cotoneaster; not on citrus, just the rose family. Where did it come from? Anybody’s guess but it could be your neighbor or at least from the neighborhood. The most effective treatment is pruning it out. But just like removing any systemic disease you have to make deep cuts to get all of it. Cut or prune out 8 to 12 inches below where you see it. Sanitize your pruning blades with alcohol.

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Cool Wet Spring Perfect for Fireblight

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Bacterial diseases like fireblight need openings to enter the susceptible plant. Flowers provide temporary openings and let this disease enter inside plants. So do fresh pruning cuts. Fireblight disease spreads from infected to uninfected plants through these openings. Rainy and windy weather helps spread this disease when flowers are open. Honeybees are suspected to spread this disease as well by visiting these flowers. Cool, rainy weather when pear and apple are in bloom, is perfect weather for fireblight disease. Fireblight is a very aggressive and dangerous plant disease that shows up as new infections in about May in Asian Pear, European pear like Bartlett and some apples. It can be a major problem on Quince as well. This is why the first evidence of fire blight disease is usually seen by the blackening of the flowers in late spring. From here it can spread into branches and cause severe problems.             But the disease problem, although unseen, can begin now. The point of entry for this disease into susceptible plants are the open flowers and fresh pruning cuts. Open flowers and fresh pruning cuts provide “fresh wounds” or points for this disease to enter inside the plant. Wind and rain are the usual culprits that spread the disease from plant to plant but even honeybees can be responsible. Fireblight has spread from a flower or pruning cut and caused more dieback.             If this disease is seen early enough (usually in late April or May) it can be eliminated easily with a few snips of a sanitized hand pruner, eliminating the infection. But the hand pruner must be disinfected between each cut on the tree or the disease can be spread on the hand pruners through each cut. Classic textbook dieback and progression of fireblight disease             There is some disagreement about what to use to disinfect hand pruners but chlorine bleach seems to be the favorite among orchardists. Heat from the open flame a cigarette lighter also seems to work. Some people suggest alcohol and others suggest household cleaners like Pine-Sol.             Plants that were infected in previous years will show evidence of this disease when new growth occurs in the next couple of weeks. As the name suggests, this damage resembles the black from fire damage. This can be confusing because any damage to pear leaves can turn black. If you are unsure, send me a picture.             We have had a surge in this bacterial disease over the past few gardening seasons because of our cool wet springs. I will post more pictures of this disease from past years on my Internet blog, Xtremehorticulture of the Desert.

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