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Locust Trees


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#1 Guest_magnetspw_*

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Posted 24 July 2006 - 03:09 PM

Last week I noticed the tips of my locust trees (four) turning brown; all locust trees in the area have brown tips. This is the recurrence of last year when the problem first occurred, tips turning brown and spreading throught the tree. This affected any locust tree I saw in my travels in the suburbs. What is this disease. I did some research and think it is the mimosa webworm. Whatever the problem, it is happening again this summer.

Last year I had Natural Way Lawn Care spray in Sept and Oct and then a late feeding in Nov. Frankly, I didn't think the spray reached the tops of my trees; they are almost 40 years old and very tall. Should I call them again and have my trees sprayed. It is an expensive treatment. Will this problem eventually disappear when the conditions are not ripe? I understand this occurs when summers are very hot.

Please advise. smile.gif

I might add when my husband and I planted these trees, we were told the locust would be an easy care tree. They were easy care when young, but today they are a lot of work, with falling brown fluff, falling thorns, falling tiny leaves on the driveway that tracks into the house, falling into gutters, falling into my dirt and cakes up. It is a messy tree, but I still value them as they are mature and I would hate to lose them.
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#2 Guest_kd7_*

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Posted 25 July 2006 - 02:12 PM

howdy-
You were advised quite correctly that locusts are very low maintenance. my first quesiton is do you have honey locusts or black locusts? Honey locusts have two insect problems: Mimosa web worm (pretty rare). and the much more common honey locust plant bug. Early summer, these little green guys are barely visible. the best way to see if you have them is to take a blank sheet of paper and shake a branch over it. you'll see a bunch of little green specks if you have them. These guys are a type of aphid that suck sap from newly growing leaves. Little half-grown tender leaves are like a buffet for them and they will suck the branch dry. This can lead to stuning and die-back, especially when severe. the good news is that the tree usually bounches right back, and the bugs die in extreme heat- all it takes is a few days over 90 degrees and they perish. Most of the honey locusts I'm seeing here in Detroit are doing great, and the tips are actually flush with a bright green/yellow growth that is a second flush of leaves.
BTW, if your tree is a black locust, are you sure you're not seeing seed pods? They finish flowering in mid-july and then form short brown seed pods (3" long or so) at the end of the branches.
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#3 Guest_kd7_*

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Posted 25 July 2006 - 02:18 PM

In re-reading your post, I forgot to mention the insecticide application. STOP DOING IT!!!!!! Never spray unless its a last resort. You kill all kinds of beneficial insects in the process, all for something that never really needed that severe of a control in the first place. Not to mention the wrong time of year. most insects are done by the fall. Any good tree care company is most active in the spring and early summer when the insects are vulnerable and before they lay eggs. Feeding is okay, but again, unless the trees are showing signs of stress, don't bother wasting your money. Never treat blindly without knowing exactly what its being done for. Mature locusts like yours shouldn't need any help now that they have a well established root system.
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#4 Guest_magnetspw_*

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Posted 25 July 2006 - 05:05 PM

Thanks for recommending not spraying.

My locust trees are 2 moraine locust and 2 sunburst locusts, so I believe they are honey locusts I believe it is the mimosa webworm that has attacked my trees, not the green aphids. It is only the tips of the trees that is turning brown but it does spread thru out the tree. Last year I saw it happening in the suburbs, my city, Southfield, Birmingham, Farmington, etc. The browning appeared late in the summer (August) and starts at the tip of the tree and soon spreads. I saw some trees that were pretty demolished by the end of the season. I was lucky and my trees did not spread that much. My concern is that doing nothing will weaken the tree further. Since the weather has been hot and dry, I have been watering daily. That is my strategy now; and do nothing else. My information was found on google http://ces.ca.uky.ed...004/h082704.htm. That article recommended biological control (apply bacillus thuringiensis) or chemical control (standard insecticide sprays). Maybe you can find this article and read it.
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#5 Guest_magnetspw_*

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Posted 26 July 2006 - 10:49 AM

Thanks for recommending not spraying.

You asked what type of locust trees I had. My locust trees are 2 moraine locusts and 2 sunburst locusts, so I believe they are honey locusts I believe it is the mimosa webworm that has attacked my trees, not the green aphids. It is only the tips of the trees that is turning brown but it does spread thru out the tree. Last year I saw it happening in the suburbs, my city, Southfield, Birmingham, Farmington, etc. The browning appeared late in the summer (August) and starts at the tip of the tree and soon spreads. I saw some trees that were pretty demolished by the end of the season. I was lucky and my trees did not spread that much. My concern is that doing nothing will weaken the tree further. Since the weather has been hot and dry, I have been watering daily. That is my strategy now; and do nothing else. My information was found on google http://ces.ca.uky.ed...004/h082704.htm. That article recommended biological control (apply bacillus thuringiensis) or chemical control (standard insecticide sprays). Maybe you can find this article and read it.

I trust you are correct in that the mature trees bounce back. Thank you.


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#6 Guest_kd7_*

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Posted 27 July 2006 - 08:30 AM

Dave Smitley from MSU had this to say last summer, and it still applies-
Honeylocust trees turning brown from mimosa webworm injury
Dave Smitley, Entomology

Throughout southern Michigan, especially the counties south of a line from Grand Rapids to Flint, mimosa webworm has built-up to damaging levels. Mimosa webworm does not usually survive our winters very well, but mild winters the last three years have allowed it to expand further north than usual. The small caterpillars web together leaves, stripping the green tissue and leaving brown lace. Heavily infested trees may turn entirely brown, appearing as if they suddenly died from drought. But even trees that are entirely brown should put out a full flush of new growth next spring.

Trees rarely die from a single defoliation, especially late in the summer. However, 100 percent defoliation two years in a row can be crippling or even deadly. The webworms go through two generations per year, with the caterpillars feeding and damaging honeylocust trees in June and July, then again in late August and early September. Insecticides applied now will not help much, since the trees will soon be dropping leaves anyways. Be prepared to apply a Bacillus thuringiensis product, dimilin or Conserve next year, when the injury first begins in late June.

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#7 Guest_Denny_*

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Posted 12 August 2006 - 03:23 PM

I have the same problem but was able to catch it this year and spray with Bt in July. Now the bottom half of my 30 ft. locust trees are clear of webworms but the top half is covered with brown foliage. I'll spray again ($14 for that tiny bottle of Bt!) later this month, but what I really need to know is how to prevent the webworms from breeding, hatching, or getting into the trees. Is there anything I can do proactively?
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