June 9

Biological Control of Aphids

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June 9, 2021


Biological Control of Aphids

Controlling pests in your garden is an arduous task to complete, especially if you’re dealing with a scaled-down type of insect that quickly reproduces itself and feeds on plant juice.

In addition, aphids are a significantly strong vector of bacterial and viral plant diseases and can be responsible for ruining your garden leaves, as they eat almost every type of plant. Really, there is a type of aphid for every plant you can conceive, even weeds.

They reproduce asexually and generate not only eggs but living aphids, which is problematic.

With this knowledge, the biological control of aphids can be an excellent choice. It reduces your garden’s exposure to pesticides, decreases environmental pollution, and prevents plant toxicity.


Biological Control of Aphids: Common Predators to Introduce to Your Garden 

This article brings together some examples of predators you can introduce to your fruit and vegetable garden. Along with the biological control of aphids, you may consider some organic options.

Lady Beetles

Lady beetles are known predators of aphids (actually, one of the most relevant). As natural enemies, these insects of the Coccinellidae family are naturally drawn to the plant louse.

You can sparingly introduce them to substantial infestations since adults can consume 5000 aphids during their whole life.

These 5-7 mm insects, red or orange-colored with black spots, are widely used to protect greenhouses and gardens, especially during the springtime, and are attracted to nectar and pollen plants, so introducing lilies, tulips and sunflowers to your garden can be a great alternative.

In the absence of prey, they would fly away looking for new ones to satisfy their appetite or inevitably die if introduced in greenhouses.

By having rich pollen and nectar flowers, your garden will always be protected from pests, especially aphids, and will be full of color and diversity, so it is a double win!

On any given day, an adult lady beetle may eat up to 50 aphids. That’s massive when you consider having a sizeable number of these predators prancing around in your garden.

A lady beetle eating aphids in succession

Entomopathogenic Fungi (Beauveria bassiana)

Another considerable method of biological control of aphids is the application of entomopathogenic fungi in infestations.

They are commercially available, especially for this use, and their use is recommended for lower aphid populations.

This fungus has a remarkable ability to infect and develop itself by using hosts, such as caterpillars and pinworms. Due to the fast reproduction of the pest, it may be necessary for more than just one application. You may use it to target other pests, not just aphids.

This biological method is very reliant on external conditions, such as: 

  • Ideal temperature ranges: 73 to 82º F (any temperature outside this limitation can paralyze the entomopathogenic growth)
  • Best function at a > 90% relative humidity 

With these conditions attended, sparingly spray coverage is necessary to establish the contact of the fungal spores with aphids.


Lacewing Larvae 

Lacewing larvae are predators of different species, such as scale insects and mites, caterpillars, whiteflies, and, of course, aphids. These delicate insects are commercially available in eggs and larvae shapes and as adults.

They must be introduced to leaves sparingly wide apart to detain their cannibalistic habits. Yes, lacewing larvae do gobble on each other for a snack. The adults feed on honeydew, nectar, and pollen, so guarantee that your garden or greenhouse has at least one of the plants that can offer these sources of nourishment.

The larvae are most recommended to be used due to their quick action and more prolonged survival. After the application, a reduction of aphids can be anticipated around 14 days.

A video showing a lacewing larva eating aphids

Parasitic Wasps  

The use of parasitic wasps is an advantageous method for the biological control of aphids. Parasitic wasps kill aphids by laying eggs in them. The larva eventually kills the aphid as it grows.

You can attract parasitic wasps by placing water plans in your garden and planting flowers so they can have access to nectar and pollen. They are also commercially available, so you can purchase a small community and sparingly release them as aphids begin appearing.


Hoverflies 

You will find these tiny black and yellow-colored insects flying from flower to flower. This is how they received the moniker ‘flower flies.’ Hoverflies bear a cross resemblance between a bee and a wasp.

They are beneficial biological control agents and will appear if aphids are present in your garden (along with plants rich in nectar and pollen for them to feed on). The female leaves its white eggs near an aphid colony, which will germinate in 2 or 3 days, depending on the temperature.

The larvae, after maturing, can consume hundreds of aphids. As a bonus, hoverflies predate other insects with soft exteriors. Your garden will naturally attract them. However, they may need a bit of encouragement if an aphid infestation spirals out of control.

Hoverflies love garlic chives, buckwheat, oregano, and other fragrant herbs, so plant as many as possible to lure them in.


Other Methods Used in the Biological Control of Aphids

In addition to the natural predators mentioned above, there are lesser-known systems put in place to control aphids on a biological level.

Aphid Banker Plants  

This method isn’t specifically based on introducing predators to lower the pest population. It is a sustainable system that provides a continual source of natural enemies, which can contain the increase of unwanted insects in your garden.

The objective of an aphid banker system is to create the right atmosphere for aphid predators to thrive.

To learn more about this system, you may find this article valuable.

While using natural predators can be effective, in some instances, you may need to double your efforts with additional control methods. Either way, we have plenty of articles on aphids that you will find useful.

Joao Lopes

About the author

Joao is an enthusiast who works as a Managing Editor at Electronic Arts, where much of his job involves researching and writing. He also has been practicing translation (ENG/ESP/POR-BR) and tries to occupy a good part of his day with an intensive load of academic studies in order to offer clients the most recent best practices. He owns a bachelor's degree in International Relations and a Certificate in Business Administration. His work covers an extensive range of clients, with services such as content writing, translations, blog writing, ghostwriting, VA, business proposals and plans, and much more.

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