Natural Control of Aphids

Half way through April and the pests begin! Okay, so I'm not in the least bit thrilled about the notion of some organisms a fraction of my size eating all my precious garden veg, but that's life. Simply put, the truth is that no gardener possesses a pest exemption card, not even myself! So, what's the first pest of the season? Well, it looks as if the aphids have made an early appearance. Setting up shop on the flowering kale plant, the aphid infestation was able to reach numbers of a small stronghold, but they were no match for this gardener. To help you in your own battle against these small insects, I'll be dedicating this post to cover my most trusted technique for the natural control of aphids.


Identification of Aphids Infestation - 
The first step for any sort of pest treatment is to identify the pests at hand. There's nothing worse than treating for the wrong pest. Not only do you risk complete ineffectiveness, you'll also jeopardize the ability for your plants to recover or the eradication of beneficial organisms. If you think you have aphids, here's a list of identifiable traits to help you solidify your notion:
Adult and nymph aphids can be seen on the bottom
of this Kale leaf. All the aphids were clustered on
older leaves towards the bottom of the plant. 
  • Size and Color - Since there are many different species of aphids, size and color will vary, but still seem to follow a similar pattern. Aphids, both adult and nymph, are visible by the human eye and will range in size from 1mm to 1cm. Their body color often has a degree of opaqueness, and can express as white, green, brown, yellow, black or even red. 
  • Large Abdomens & Thin Legs - Under close observation, the six long and thin legs of aphids can be seen. The observer will also be able to identify the small head containing a pair of long antennae and the large abdomen directly behind. On the rear of the aphid body, there will be a characteristic tail-like extension known as the cauda.
  • Location on Host Plant - Location is a dead giveaway for aphids. They tend to cluster on the undersides of leaves. Especially on new growth, or older and stressed leaves. You may sometimes find a stray aphid on top of leaves, but for the most part, look from the bottom up!

Natural Aphid Control - 
Now that you've managed to successfully identify the problem, it's time to move into how to get rid of aphids. Since I've never been one to support the use of solve-all chemical insecticides, you'll find that my technique for the natural control of aphids is broken down into two efficient phases:
Flowering Kale with the Garlic Water insecticide.
All leaves that were heavily infested were removed
and burned on the BBQ. The rest of the plant was
misted with the garlic solution. 
  • Physical Removal - Realizing that aphids can affect a wide variety of hosts, physical removal may not always be feasible, especially with large crops or trees. If on the other hand you can do some physical removal, it's highly recommended. To drastically slow the growth of existing aphid infestations, remove any leaves containing large numbers of the pests. Incinerate the highly infected leaves and use your fingers to squish any visible aphids left on the host plant. 
  • Organic Aphid Control - Decrease their numbers with physical removal, then knock 'em out for good with an organic control of aphids. For this phase, I've found that misting the entire foliage of infected plants with a garlic spray inhibits growth of the aphid population, as well as prevents against further infestation. For an effective garlic spray, use a mortar and pestle to create a garlic paste out of two cloves of garlic. To the garlic, add two tablespoons of rubbing alcohol (70%) and combine well. The garlic/alcohol mixture should be poured in a spray bottle with one cup of water and just a couple drops of liquid castile soap. Shake well and immediately use the mixture to mist plants lightly on both tops and bottoms of foliage. 

Why the Garlic Spray works - 
If you've already done some research into garlic sprays for getting rid of aphids, you'll notice that the preparation for my recipe differs from most others. The common recipe calls for cloves to be blended and left out in a solution of water to soak for a day or two. I think of this step as unnecessary and actually detrimental to the potency of the insecticidal properties of garlic. Here's my reasoning: Allicin is the active component in garlic that serves as an insecticide. It is a short-medium lived molecule that is created when garlic cloves are crushed. Since the allicin molecule contains an OH group, it is only slightly soluble in water, with increased solubility in alcohol. Therefore, it makes no sense to rely solely on water as your distribution medium. The rubbing alcohol is added to increase solubility of the allicin molecule into the solution. Furthermore, the mixture is used immediately as opposed to being left out to soak. This is because allicin decomposes quickly (half life of six days), and is much more concentrated when used quicker. Oh, and if you're wondering what the soap is there for, it's to help break water tension and help the solution adhere to the leaf surface better!


Word of Caution - 
While this organic treatment for aphids will be efficient in eradication, it could also eliminate beneficial organisms you wish not to get rid of. To minimize this potential, only use the garlic spray when you are 100% certain of your targeted pest! If the proper physical removals can be performed, garlic treatments should remain minimal. Thank you for reading this post on the natural control of aphids.