Ants are eating Potato plants.
Hello; Ants are eating Potato plants.These are Black about 6 mm long ants. Several of them gather around the main stem of a plant and eat it making the stem narrow -looks like what beavers do to trees. They continue until the plan dies. So far they killed 4 plants. I tried soap and water, no effect. I put cinnamon on and around the stem, this kept them away for some hours but they came back and started eating the stem at a higher place. I know many believe ants don't eat potatoes, they put Aphids on plants but I am sure, I saw them and watched carefully there is no other insects. Any suggestions?
Montgomery County Maryland
Hi- could you please send photos- close-ups of the ants and the damaged stems? As you mention, ants will protect and herd aphids to secure the honeydew excreted by the aphids. Ants are decomposers; they collect and chew dead and decomposing plant material. They are not plant pests.
Can you see any aphids on your plants? It's possible that some type of insect pest is feeding on your potato stems at night, such as cutworms.
Based on your photos, we suggest cutting a few freshly wilted potato stems to see if a boring insect, such as potato tuberworm or wireworm, may be infesting your plants.
This is a fairly comprehensive NC State U. web page on potato insect pests. We have the same pests, with lifecycles a few weeks behind NC.
Sorry I forgot to mention, I push the soil down to be able to take picture. Ants attache themselves to the Main stem right at the soil line. They do not bite anywhere else on the plants.
We suggested slicing open a potato stem to determine if there was another cause for the feeding injury and wilt symptom. This would require sacrificing an affected plant- pulling it out and cutting the stem vertically. Any potential boring insect larva would be visible to the unaided eye.
Although ants do not typically consume live plants it is certainly possible, as you've witnessed, that an ant population has taken a liking to your potato plants. There could be a lack of other, more commonly accessed foods.
Cinnamon oil is a low-risk insecticide used to repel insect pests. Pure cinnamon could possibly kill ants or other insects. Diatomaceous earth is another organic insecticide that can repel and control pest populations when sprinkled on the soil around plants and on plant parts requiring protection.
Thanks for detail explanation. One question, do I need to reapply Diatomaceous earth after each rain? In another words, would rain wash out the Diatomaceous earth and Cinnamon oil?
Probably not not necessary to re-apply after a light rain, but definitely after heavy rainfall.
Hi- we can't identify the insect on your hand. The 2 cm long insects you found are most likely some type of soil invertebrate, harmless to plants.
Thank you for the interesting and unique photo of ants clustered on the damaged potato stem. We had not seen this phenomenon before now.