Aphids are one of the most common and destructive pests for growers worldwide. They can develop resistance to insecticides, and are not very picky when it comes to food sources which can make them tough to eliminate from the grow room completely.
What are aphids?
Aphids are small, soft-bodied, sap-sucking insects that feed on a wide variety of plants all over the world. They come in a variety of colors ranging from green to red, to black. There are even some that have a fuzzy white layer that makes them resemble cotton or mealybugs. All aphids are contained in the Aphidoidea family but can range in size color and characteristics greatly. In fact, there are over 4000 species of aphid throughout the world.
They have some very characteristic features, which allows for easy identification, even with species that you have never seen before. Aphids have 2 whip-like antennae on their heads, a pear shaped body, 6 legs, and 2 tube-like structures on the base of their body called cornicles. These cornicles are exclusive to aphids and makes it easy to identify with certainty that the pest you have found is indeed an aphid. If these cornicles are not present, it is not an aphid you are looking at.
Aphids are incredibly potent insects, which can reproduce and grow a new colony both sexually and asexually. Only one aphid is needed to start a colony, and some have even been found to be born pregnant. This allows incredibly rapid development of colonies,that can seem to pop up overnight.
Aphid colonies can grow very quickly and affects what kind of aphids are born. In small colonies, aphids are wingless and have low mobility. As the colony grows, however, more and more aphids will be born bearing wings which they use to fly to new locations to begin new colonies.
Small aphid numbers are usually not a problem for your plants and not in need of strict aphid control. If their numbers are allowed to grow and reach large colony sizes, however, they can cause your leaves to curl and can stunt future growth of the plant.
Aphids drink the sugary sap from inside your plant's stems and leaves, and as a result, their feces is pretty much pure sugar. This makes it sticky, and a perfect vector for fungus or bacteria to grow. This means that a large aphid infestation can greatly increase the chance of a bacterial or fungal infection as well.
Aphids can be a challenge to control since they can actually develop resistance to many insecticidal sprays. They are even more challenging to control in the presence of ants. This is because ants feed on the honeydew produced by aphids, and once finding a colony will cultivate them for food. They will move aphids around the garden to inoculate new plants and escape attempts of human control.
That said, there are a few methods that still work today when it comes to controlling aphid populations. Such as:
1. Rinse them off with water
The first step of control should be to physically blast off as many aphids as possible by running the leaf tips with water. This will free a large portion of the infected leaves from the aphids without using any insecticides.
2. Use insecticide sprays and soaps
Once a large number of the aphid colony has been washed away with simple water, it is time to use insecticidal soap or sprays to free hit the remaining aphids. You can use insecticidal soap, horticultural oil, or pyrethrum sprays to effectively treat aphids using safe and food friendly insecticides.
3. Diatomaceous earth
Diatomaceous earth is a great additional treatment to ensure the smaller or hidden aphids still get caught. This product contains microscopic aquatic animals that have become fossilized and are razor sharp. There are no chemicals in this product and it is highly effective as a “leave-on” treatment for a wide range of insects. It comes as a powder and as a soft-bodied insect moves over the powder it is sliced up by the sharp fragments of the diatomaceous earth, resulting in their death.
4. Pinch them off
Anytime you see an aphid, the best thing to do is pinch it off. This is very easy to do since aphids are not fast moving insects, and their soft, swollen bodies are easy to pop with your fingers. For most expert growers this is just a regular part of the process of going through and checking the leaves of plants for signs of deficiencies and insects.
5. Beneficial insects
This is a great method of control, especially for organic grows. Aphids are incredibly hard to eliminate completely. Once an infestation occurs, it is highly unlikely that this particular crop will be completely aphid free ever again. Choosing to spray or manage the aphid infestation while it is large, and then introducing predatory or beneficial insects as a sort of “aphid police force” is a great idea and is usually enough to keep the populations down to manageable numbers. As mentioned earlier in this article. Small colonies of aphids will not harm your plants. It is only the large, uncontrolled aphid colonies that can have significant impacts on your yield and plant health.
6. Nutritional treatments
For very large colonies that you are having a hard time treating, it can be helpful to change the nutrition your plants are getting for a short period of time. Aphids love new leaf growth since it has not yet developed a hard cell wall and is easy to suck the delicious sugary sap from them. High nitrogen fertilizers promote this type of growth on your plants and can make it very easy for aphids to find food and thrive. By changing the nutrition to include fertilizers higher in potassium, or using more organic fertilizers that break down slower, or simply holding off fertilizer a little bit and delivering only ¾ or half doses while combating the aphid infestation can help minimize the food source of aphids and help with control.