biwa
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Small black ants tunneling through plum tree

I cut a dead branch off my plum tree today and a bunch of ants came out. They were making tunnels in the bark.

Is there something I can do to make the plum tree better able to withstand these pests? For example, I found that when I raised the pH around my willow tree it got healthier and withstood aphid attacks much better. Is there something like that I can do for the plum tree? Fertilizer maybe?

This plum tree is the type with red leaves, dark purple fruit, and soft wood. It has sap leaking out (perhaps woodpeckers trying to eat the ants?) and one of its branches has dropped its leaves prematurely. I suspect the pH around the tree is slightly acidic because the viola love it there.

wingdesigner
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Ugh. It sounds like they're pretty well established, carpenter ants. Better check your house or the nearest structure for infestation, as well. And I may get blasted for this next advice, but if you can keep kids and pets away, put down some powder that kills ants at the base in about a foot-wide band. Depending on how much of the tree has already been infested, it may or may not be too late to save the tree. Carpenter ants like wet, soft wood, so something else attacked your tree and started rotting it from the inside out. I doubt that ph is the major player at this point. The tree may be suffering from some kind of blight, do you have any pictures you can post? Include both healthy, sick, and dead parts. Are there any breaks in the bark on the trunk?

JONA878
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Hi Biwa,
Ants usually infest a tree only if there are a lot of ahids around.they feed on the honey dew that the aphid produce.
I guess that if the bark was very loose and holey they may try to set up a small nest in it as well.
A good way of keeping them off would be to put a grease band around the trees trunk. One of the ones that would normaly be used to keep winter moth at bay on apple trees.
They would not be able to cross that and you would not have to worry about spraying etc.

Jona.

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bewildered_nmsu
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Both Jona and Wingdesigner are on the right track. It could also be wood borers ( the larval stage of a beetle). I find that for any insects actually living inside the tree an imidacloprid based systemic insecticide is the way to go. Bayer makes a systemic insecticide that works very well.

a0c8c
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I'm not big on pesticide, never have been, but when it comes to carpenter ants, I poison them every time. It's not worht riskign your house, as they can destroy a house in under a year. We've got a big problem with them here in Texas, so much so that Andro gives out free poison up to 3 times a year in Austin to help out(and promote of course). They're almost as bad as the red hell called Fire Ants.

biwa
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Location: Virginia, zone 7

Oh wow, I have carpenter ants? That's horrifying.

There are cracks in the bark. The tree has 5 trunks. One was the dead one I found the carpenter ants in. Another trunk looks like it may be dying (it has already dropped its leaves and fall has barely started). There's still 3 healthy ones left.

Does it matter what kind of oil I coat the bark in? How about canola oil or vegetable oil? Can I put a band of oil around the lower parts of my house to protect it as well?

If carpenter ants indicate a aphid problem, maybe I need to go after aphids too? Is there something that can be done to keep aphids off the tree?

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rainbowgardener
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It would help to work on the aphid problem, but you need to work on the aphids and the ants. Carpenter ants have been known to bring aphids to plants; they "farm" the aphids for the honeydew.

Horticultural oil is usually mineral oil not vegetable. You want something that's emulsified so you can mix it with water and spray it on. The idea is that it clogs the insects spiracles so they can't breathe. I don't believe you would get the same effect painting the oil on, especially not vegetable oil.

frinda
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thanks for this discussion. Sounds like a summer oil spray is the way to go with my sugar ants. I'll give it a try.



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