Got Ants in Your Plants?
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Question. Mike: Could ants be stealing my tomatoes? Last season I had eight plants in a little fenced-in patch. The disappearances began just as the first fruits were turning red. Some tomatoes were just gone; others had large sections removed. I had always seen ants around, but paid no attention until I noticed some on a half eaten tomato. Is it possible these little workers were stealing and storing my summer crop for a winter feast? If so, what's the safest way to handle the culprits without killing any beneficial garden inhabitants like frogs and spiders? Sincerely,
- ---Brian in Virginia Beach, VA
Answer. The ants are not guilty, Brian; but I love the Warner Brothers cartoon image you evoke of an army of worker ants wearing little lighted helmets and making off with your love apples in the middle of the night. The much-less romantic truth is that the ants were simply attracted to already damaged fruits.
When entire tomatoes are gone, the culprits are generally marauding mammals, specifically squirrels and/or raccoons. (Or sometimes love apple-envious neighbors.) A motion-activated sprinkler is the best protection against these ingenious and acrobatic enemies (and the neighbors too; listen for wet screams in the middle of the night). Slugs could also be responsible for the half-eaten love apples. Test for their presence by putting some beer traps out at the base of the plants in the evening one warm night this season. If the traps are full of dead drunken slugs in the morning, follow up with an iron phosphate slug bait.
Question. Can you please tell me the most effective way to control ants in the garden? They're causing a lot of damage to my crops, especially to seedlings. I tried several natural repellents and they did not work, so now I'm looking for something that will eliminate the ants rather than repel them. Thank you,
- ---Sandy in Braham, Minnesota
Answer. I don't think that you've fingered the guilty party either, Sandy. Ants are known to make off with freshly sown seeds, but they don't normally attack seedlings. And, again, the only time they usually go after crops is when something else has already damaged the edible in question.
The biggest garden problem that ants definitely cause is their protection of aphids and other plant-sucking pests, so that the ants can consume the sweet 'honeydew' the pests excrete. When aphids are abundant, ants are often to blame.
Otherwise, most experts feel that ants are actually beneficial in the garden. They aerate the soil and prey on the egg and larval stages of many true pests. In addition, they are the natural enemies of termites, constantly raiding underground colonies to attack and consume the young wood-eaters-to-be. This pressure helps keep termite populations low, and keeps the worker termites busy fending off the attacking ants—leaving less time for those creatures to try and find your framing. So be warned that killing ants outdoors could actually increase your pest problems.
The three biggest 'consumers' of new seedlings are the afore-mentioned slugs, the nasty underground caterpillars known as cutworms, and small mammals like field mice and voles. This Spring, put out beer traps in the evening to check for slugs; surround new transplants with collars to protect them from cutworms; and place some mousetraps baited with peanut butter nearby to catch any vermin.
Question. Mike: Every year, ants get into my raspberries once the fruit starts arriving, which is usually not until August. Can I do anything to stop them early in the season? Or do I have wait until mid summer when the ants start to appear? Thanks,
- ---Kathleen in Greenwich CT
Answer. First, if you're cutting, mowing or otherwise molesting the old canes in the fall or Spring, stop! Many raspberry varieties bear twice; at the very tips of the canes late in the summer of their first year and then up and down the entire length of those canes early the next summer. In my garden, this 'second harvest' generally produces lots more berries than the first run, which, like yours, often arrives so late in the season that you lose some of the fruits to frost. (See this previous Question of the Week on raspberries for more details.)
Now, there is a chance that your ants are also just being opportunistic. Yellowjacket populations are peaking during the late summer/early fall raspberry run, and these creatures are notorious for attacking the fruits just as they ripen. Ants often then move in to feast on the damaged fruit. If that's what's happening in your garden, use yellowjacket traps and/or row covers to protect the fruits from initial attack and your ant problems should be few.
If, however, ants are the only issue—or persist after you control the voracious wasps—spread boric acid traps throughout the raspberry patch. You can buy packaged traps and bait or make your own with the recipe in this previous question of the week on ants.
But the traps, which combine a low dose of boric acid with sugary bait, should ideally be made bee-proof when used outdoors. So place the traps inside a jar in which you've punched a few holes in the lid or under a shoebox with some small holes cut out. This should allow access to ants, but not bees drawn to the sugary part.
Indoors or out, you must not otherwise harm any ants you're using the traps against. The only way to control ant problems is to wipe out the queen and thus the entire colony. So the foraging workers must be allowed to take the slow-acting bait back to the nest, where the boric acid will begin to have its deadly effect after five to seven days.