What Temperature Kills Aphids? Here’s The Truth

Aphid populations seem to keep coming back every year, however hot or cold it may be. So it is natural to wonder: what temperature kills aphids? Let’s find out.

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Aphids are tiny pests that feed on the plant sap of your precious plants and infest your gardens.

It is hard to get rid of them because they reproduce quickly and keep appearing back despite applying most pesticides or organic treatments.

Sometimes, you might not see them during the winter, but they will suddenly come back as soon as the summer/spring season comes.

This is because they either hibernate or lay eggs that can overwinter, hidden on the underside of leaves. While most aphids can survive summers, some become weaker and may die at high temperatures.

So what is the ideal temperature to kill aphids? Let’s find out.

 

 

What Temperature Will Kill Aphids?

Most aphids can survive hotter temperatures but cannot live in extreme cold. So how low should the temperature be to kill aphids?

Well, temperatures between 23 to 5 F are typically enough to kill them. On the other hand, some aphids may not survive in temperatures higher than 90 F.

If aphids are on healthy plants, they are able to fall down to the ground under the plant’s shade which protects them from high temperatures.

Research shows that in some species of aphids, such as pea aphids or green peach aphids, heat tolerance is governed by the Buchnera bacteria.

These aphids are associated with the Buchnera bacteria in a symbiotic relationship, and their tolerance to heat depends on which genetic variant of the bacteria they are symbiotes with (more about this later).

Can They Die When It’s Cold Outside?

Yes, aphids can survive when it is cold outside as long as temperatures don’t fall abnormally low. Some aphids show excellent cold resistance and are quite active in the winter months.

They lay eggs prior to the start of winters that can survive the coldest months of the year to hatch in spring or summer months.

Some aphids also have glycerol and mannitol (anti-freeze proteins) in their body that helps them to survive in the winter.

Such aphids are more affected by hot temperatures. They show reduced activity and don’t procreate as much, either. It is easiest to get rid of aphids during the summer.

 

 

How Do They Survive in The Winters?

Aphids use a number of strategies to survive the winters, be it laying eggs in winter or dropping their body temperature.

• Male and female aphids breed in later spring, and the female lays eggs that overwinter. Most aphids survive the cold months as eggs.
• Some aphids reduce their rate of metabolism in winter like larger animals do during hibernation.
• Some aphids have body fluids that freeze, and their proteins get dissolved so as to avoid the crystallization of water inside the aphid’s body.
• Some aphids make their body temperature lower than the surrounding temperature to become resistant to extreme cold.

How Can You Kill Them in the Winter?

There are no specific techniques to kill them in the winter. If you are facing aphid eggs that are overwintering on your plants, you can introduce parasitic wasps that feed on them.

Another way is to clean the affected area with a solution of insecticidal soap. You can also spray natural insecticides on your plants, such as neem oil.

Another effective method is a biological control for active aphids feeding on their host plants. This involves introducing beneficial insects such as ladybirds which are predators of aphids.

Why Some Aphids Can’t Survive Summers?

Aphids consist of numerous subspecies. Some can survive the summers, while others can not.

To understand this, we need to understand the symbiotic relationship between some aphid species, such as Acyrthosiphon Pisum and a Buchnera aphidicola.

Both cannot survive without each other. Aphids provide shelter to the bacterium, while the bacterium provides essential nutrients to its host.

The bacterium produces two kinds of genes: one heat-tolerant gene and another heat intolerant. A single mutation can change the type of the gene, thus affecting the host organism.

Aphids that host bacteria without the heat-tolerant gene cannot survive in the summer. Many studies show that the bacterium dies when heat is applied. So, the host aphid fails to get the essential nutrients and dies or becomes dangerously weak.

Female aphids can reproduce asexually and can produce clones of themselves. Research shows that aphids exposed to high temperatures may not be able to reproduce.

 

 

Frequently Asked Questions

What kills aphids instantly?

You can make an alcohol-based insecticidal solution to kill aphids instantly.

You can mix equal parts of water and 70 percent alcohol in an insecticidal soapy water emulsion, or you can use store-bought chemical Insecticidal soap spray to kill aphids instantly.

Can aphids survive the heat?

Yes, some aphids can survive temperatures up to 90 F but may become weak in the summers.

Studies showed that the ability to survive heat differs for different species of aphids, and the temperature significantly impacts the aphids’ life cycle and metabolism pattern.

Do aphids lay eggs in the soil?

No, they generally lay eggs on the undersides of leaves or stems and secrete a sticky substance (honeydew) which helps to adhere the eggs there.

Even root aphids lay eggs on the plant, and once the nymph hatches, it can fall off into the soil. Some root aphids are known to burrow in the roots to lay eggs.

Why do aphids keep coming back?

Aphids have a life span of only 30 to 40 days, yet it seems impossible to control an aphid infestation. The reason behind the problem is the high reproductive rate of female aphids.

Aphid females can produce clones, which is why they can create as many as 12 copies of themselves a day.

Moreover, aphid eggs overwinter, and nymphs come out during the summer giving the impression that aphids keep coming back every year.

Wrap Up

You can kill aphids by exposing them to high temperatures. While some species can survive temperatures up to 90F, most will die or show become inactive at such temperatures.

Aphids can survive cold temperatures up to 5F. They can also survive colder temperatures by laying eggs, hibernation, and other defense mechanisms.

Letter 1 – Aphids and Lady Beetle on Milkweed

 

Subject: yellow worm/ larvae/ milkweed plants
Location: traprockridge Plainville CT
August 7, 2014 12:54 am
Here is an aadditional photo to add to my original question of what are the yellow larvae worm ? things eating the milkweed pods. You can also see the red beetle to the left.
Signature: hopefish

Aphid Infestation and Lady Beetle on Milkweed

Dear hopefish,
We did not see any additional submission from you.  You have a major infestation of Milkweed Aphids or Oleander Aphids, Aphis nerii, and since Aphids release honeydew, it also appears you are getting a black buildup on the plant.  None of this is healthy since Aphids suck juices from plants.  The beetle is a predatory Lady Beetle, but that single Lady Beetle will not put a dent in this Aphid infestation.  We would recommend attempting to control the Aphid population, but without pesticides as those will have an injurious effect on other creatures that feed on milkweed, including Monarch butterfly caterpillars.  See BugGuide for additional information on the Oleander Aphid.

Letter 2 – Aphids: Why have the chickens stopped laying????

 

Black bug orange legs
Location: Bisley, Glos
May 16, 2011 12:44 pm
100,000s of these on my chicken shed all over the place have been there for a couple of weeks wandering around not sure what they are doing or where they have come from have got a common xmas tree next to it have they hatched in it? what do I do with them the chickens don’t like them and have stopped laying
Signature: olivia

Aphids and a Mystery

Dear Olivia,
In our haste to respond to as many identification requests as possible so that we can get back to formatting the powerpoint presentation we are giving at the Theodore Payne Foundation in two weeks, we are firing off single word identifications.  We continued to read your letter as we hit send and we halted at the comment you made about the chickens having stopped laying.  Since Daniel had a bad experience with chickens last year and he plans to get three more hens in mid June, your comment seemed to warrant further exploration.  These are Aphids, and the presence of the conifer tree nearby might indicate that they are Giant Conifer Aphids in the genus Cinara, but your photos are not that sharp and accurate species identification might not be possible.  It is intriguing to us that chickens, which are known to love insects, are shunning these Aphids.  We don’t have an answer, but perhaps one of our readers will be able to provide insight.  We wonder if the appearance of the Aphids might be related to the egg laying moratorium.  Again, we don’t know, so we pose this as a Mystery.  We are also going to feature your posting in our banner of changing features in the hope of getting you an answer.  If you supply a comment to the posting, then you will be notified if there is an additional comment in the distant future as we delete answered emails and we do not maintain contact information.

Letter 3 – Biological Warfare: Syrphid Fly Larva and Ladybird versus the Aphids!!!

 

Larva Verification
I returned home last weekend to find my rose bush laden with aphids. A quick search of my garden located a lady bug which I then "transplanted" onto a stem of the rose bush. From the photo it can be identified as a 7 spotted lady bug. I found a dozen more lady bugs and carried them to the bush where each remained on top of its own rose stem. Since this was my first attempt to fight aphids with lady bugs rather than to zap them with an insecticide, I became more and more enthralled with watching the daily activities on my rose bush. Then I noticed "worms" appearing. From what I had read about lady bugs, the larvae were described as looking like alligators, but my larvae don’t have that appearance. Is this because they are relatively young and in beginning stages of being "larvae" or am I looking at something entirely different. One of the photos shows a larva on a leaf. The other photo I took to show how the large was wrapped around the twig. Just as I snapped the photo, an aphid crawled past and the larva snatched it up and is shown eating it. To make a long message short, are the two larvae in the photos actually lady bug larvae? I love your web site!!!! Thank you for your help
Jean
Republic, Missouri

Syrphid Fly Larva	7 Spot Ladybird

Hi Jean,
No. Your larvae are not Ladybird Larvae. They are Syrphid Fly Larvae, and they are a wonderful biological control agent against Aphids, as are Ladybirds. Lacewings are also marvelous. If the Aphids ever become too numerous for the predators, a jet of water from the hose will knock them off the plant and without a food source, the wingless young will perish. Thanks for the great letter and the accompanying photos. We have photos of Ladybird Larvae on our Ladybug page.

Dear (Bugman), Yesterday I went you photos regarding the ladybird larvae which turned out to be syrphid fly larvae. Thank you so much for your response and your answer. I think your site is one of the most helpful I have ever seen…. so personal and interactive! I am a Master Gardener and webmaster for the University of Missouri Master Gardener’s website for Southwest Missouri http://www.extension.missouri.edu/greene/mgg/. I would like your permission to add your site to our link page. Please let me know if this is feasible.
Jeanne Larsen
Republic, MO

Letter 4 – Citronella Ants tend Root Aphids

 

Subject: These aren’t salamanders!
Location: Halifax, Nova Scotia, Canada
April 25, 2016 9:32 am
Hi BugMan,
I was recently on a salamander hunt in an urban forest environment when I came across the following nest under a rock. I leaned in close and was surprised to see that the round white ones had legs (and antennae) and were not just larvae as I had thought. I’ve included two photos: the first being the overall view of the hole beneath the rock and the second a closer view of the larvae (?).
We’ve had some issues in the recent past in the Halifax region in Nova Scotia with fire ants creeping up and I thought I may have come across one of their nests while in the woods (“woods” used very loosely as I can see houses if I squint and hear the highway in close proximity). After spending awhile searching through the life cycles of various ant types, I then wondered if perhaps I had happened across ants feeding upon the larvae of another insect. I’m hoping you’re able to clear up my my confusion, but in the meantime I’ll keep searching – maybe the actual paper insect ID book might be helpful.
If it makes any difference, the area where I found the nest is a few metres away from a small area of wetland and we have had a relatively mild winter so there was not a lot of snow melt.
Signature: NatureGirl

Citronella Ants tend Root Aphids

Dear NatureGirl,
You have happened across Ants, but instead of “feeding upon the larvae of another insect” they are harvesting honeydew from Aphids.  We did not recognize either your yellow ants or the white Aphids, so we searched on the web and quickly found the Cornell blog New York State IPM Program and a posting of Citronella Ants caring for or tending Root Aphids.  The site states:  “The life and habits of citronella ants aren’t well-studied, but they do have one fascinating trait. They tend herds of underground aphids, known as root aphids as if they were cattle, and harvesting sweet honeydew excreted by the sap-loving aphids. Root aphids feed on the roots of shrubs and plants.”  Additional images and information can be found on Wild About Ants, Scientific American and BugGuide.  

Citronella Ants tend Root Aphids

Letter 5 – Katydid Nymph and Aphids from Australia

 

Australian Katydid Nymph/ Share the love
Hi "What’s That Bug",
I found your fascinating site when looking for information about katydids, and thought that in the interest of science and bug-lovers everywhere you might appreciate some contributions from Down Under. Attached is a very new, shiny katydid nymph. Also for your "bug lurve" section, please find attached a gratuitous aphid orgy.
Warm regards
Jennifer

Hi Jennifer,
Thanks for your contributions. We aren’t entirely sure the aphids are mating. Many Aphids have generations that reproduce parthenogenetically. The females do not require a mate and give birth to live females. In this way they can reproduce very rapidly.

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