Help! Black ants are killing my tomato plants.

AthanatsiusJuly 29, 2011

At first, I thought perhaps my yellow pear tomato plant had Fusarium or Verticillium wilt. One branch at a time was turning yellow and wilting.

But it was happening so fast! Each day, several branches would wilt and yellow. Then as I was inspecting the plant and pruning off dead branches, I saw a hole in the ground next to it. There were black ants, which looked like carpenter ants, streaming in and out of it. I sprinkled some Sevin dust around the hole, hoping that would take care of them. But the plant continued to die. Today, when it became obvious the plant would not pull through, I pulled it up to examine the roots. The tomato was a transplant, and I had planted it together with it's 1 quart peat pot in the ground. Despite the Sevin dust on the surface of the ground, There were healthy looking black ants swarming in and out of the peat pot!

The soil in the peat pot was a different texture from the surrounding soil, so this may be why the ants were attracted to it. The ants were also carrying some white matter which was in the potting soil. I am not certain if the ants were eating the roots to the plant, merely nesting in the pot, or eating the white specks of matter which was in the potting soil. Whatever their motivation, they killed my plant within only a few days.

Now the Sweet 100 plant next my yellow pear is showing the same symptoms. I sprinkled Sevin dust all around on the ground, more than before, but I think it would be more effective if I drown them with a liquid containing some safe organic pesticide that will not ruin the tomatoes.

Any ideas or suggestions? If what happened to my yellow pear is any forewarning, I do not think it will take long for my Sweet 100 plant to die.

Has anyone else had this to happen? Does anyone have any suggestions?

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jean001a(Portland OR 7b)

First, ants don't eat roots.

The white stuff they were carrying were likely pupal cases.

Next time you plant, regardless what the directions/seller says, remove the peat pot. It restricts the root system unless continually moist. And if any part is above the soil, it wicks moisture out of the rootball. A very bad thing.

    Bookmark   July 29, 2011 at 11:14PM
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missingtheobvious(Blue Ridge 7a)

I've read about ants making nests in the roots of a tomato plant, with the result being a dead plant. I think the problem is that they remove enough soil that the roots dry out.

Here are some home remedies which shouldn't affect the tomatoes:

= Sprinkle diatomaceous earth (DE) in a ring around the nest. When ants walk through this, it pierces their exoskeletons and they will die. [DE is a rough white powder, the fossilized skeletons of diatoms, a type of algae. It is sold in some garden centers. You could also try agricultural supply places or stores that feature organic foods and other natural products.]

= Mix 1 cake of yeast with 1/3 cup of sugar and 1/3 cup of molasses. Put it in low lids near the ant nest. Ants love sweets and will take it back to the nest; the yeast will expand inside their bodies and kill them. [Freeze whatever you don't use.]

= Crush grains of white rice with a mortar and pestle. Sprinkle it around the anthill. The ants will take it inside the nest. It will expand inside their bodies and kill them. (Some people use grits instead of rice. Powdered tapioca should work too.)

= Mix 1 part sugar with 2 parts borax. Add enough water to make a gel. Put this bait on squares of cardboard or low plastic or metal lids (low enough that ants can enter and leave easily; you can also raise the dirt around the sides of the lid to make a ramp). The ants will take this back to the nest and they will all die. [Too much borax isn't good for tomatoes, so don't use a lot of this in the garden.]

    Bookmark   July 30, 2011 at 12:08AM
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