Aphids are a constant battle, no matter what level of gardening you’re at. An expert struggles with aphids on a regular basis. There are ways to incorporate aphids into your life in a beneficial way. It just means having some tolerance and some patience.

At TreeTime Greenhouses no pesticides are used. Sherrie Benson, the Head Grower and Horticulturist at Treetime Greenhouses uses an Integrated Pest Management System that involves the use of various biological controls. In this Gardening at USask video, Sherrie shares her insights into natural aphid controls. 

Understanding Aphid Habitats

  • Growing Points: Aphids love to hang out on the growing points of plants. If you inspect the stems’ growing points, you’re likely to spot these pests. 
  • New Growth: Aphids are attracted to soft, tender new growth. Their affinity for the food source becomes particularly apparent when it’s soft and tender.
    • Example: the runners of wild strawberries. 
  • Unhealthy Plants: Unhealthy plants are also susceptible to aphids as they produce higher sugar levels. This is a higher energy source for the aphids. They feed on the sap inside the plant (xylem and phloem).

Identifying Aphids

  • While it’s not crucial to identify specific aphid varieties, it’s essential to recognize that there’s a multitude of them. They can be a variety of colors including black, green, red, yellow or brown. Some may even have a woolly substance around them, such as the Woolly Elm Aphid.
  • Many gardeners bring home plants from garden centers, and with those plants often comes the Green Peach Aphid.
    • Green Peach Aphid is a nice lime green color.
    • Aphids also have cornicles, which are like tailpipes that stick out the back. Green Peach Aphids have little black tips on their tailpipes.

The Intricate Aphid Life Cycle

  • Understanding the life cycle of aphids is key to managing their populations effectively.
    • Aphids are born pregnant and reproduce at a rapid rate. They are able to give birth to 5-7 Aphids every single day that they are alive. This can result in an infestation very quickly.
  • All Aphids are born with the ability to develop wings.
    • This is a survival mechanism. Wings start to emerge when the population on a plant becomes overcrowded, allowing them to move onto another plant.
    • When you have winged Aphids, this signals an infestation level that requires attention. It is time to find ways to encourage their natural predators and parasitoids. 

Embracing Natural Predators

North America is rich in natural predators for aphids, eliminating the need for pesticides.  Parasitic Wasps, Ladybugs, Lacewings, Hoverflies, and Carab Beetles play crucial roles in controlling aphid populations.

Parasitic Wasps: Are tiny wasps that are only a couple millimeters in length. They are usually black in color, with some of them being slightly yellow. Their life cycle plays an important role in Aphid control.

  • The adults feed on the nectar of blooms and then make their way to an Aphid infested plant.
  • The Parasitic Wasp injects a toxin into the Aphid that shuts down the Aphids immune system, while also implanting an egg into the Aphid.
  • After being parasitized, the Aphid will continue on with their normal routine for around 5 days. After the Parasitic Wasp egg hatches, the larva starts to devour the insides of the Aphid, and the Aphid exoskeleton eventually becomes mummified and stuck on to the leaf.
    • This will look like a little brown blob, which is unsightly but is not doing any damage to the plant.
    • Do not remove the mummified exoskeleton as that could kill a Parasitic Wasp larva that has yet to emerge. 
  • To encourage the presence of Parasitic Wasps, maintain blooms for as long as possible. 

Ladybugs: We have two types of Ladybugs in Alberta.

  • The Ladybug native to Alberta is the Two-Spotted Ladybug and we don’t see that one frequently. But it is starting to make an appearance more and more.
  • We see the European Seven-Spotted Ladybug much more readily. It does not pose a large problem, except for pushing our native Ladybug higher up in the tree canopy. 
  • It is important to be able to identify Ladybugs in all of their stages so you do not mistake them for a pest. They excel in providing pest control as they eat Aphids and other soft-bodied insects throughout their entire life cycle.
    • When they are young they look nothing like a Ladybug. They are quite ugly and in their larval stage they are a little black ball just waiting to pupate. 

Lacewings: In their adult stage they are lime green or brown with very delicate, large wings.

  • In the adult form they are a pollinator. But in their larval stage they are commonly referred to as an Aphid lion. They are capable of devouring entire aphids within minutes. 
  • Pupation Stage:
  • This is when the Lacewing larva are going through metamorphosis to turn from the larval stage to the adult stage.
  • This will often appear on the underside of leaves. It looks like a tiny string with a white ball dangling from the end. 
  • Do not remove these as you want them to finish their life cycle and go on to pollinate your plants.

Hoverflies: Bee mimics that are often confused with a bee or a wasp.

  • Effective predators and indicators of aphid presence.

By educating yourself on these natural predators, you can learn how to encourage their presence in your garden and they can give you a hand with a troublesome aphid problem.

Providing for Your Garden’s Protectors

  • By understanding the lifecycles and the needs of these predators you can make accommodations for them.
  • One of their biggest needs is water. Like humans and animals, insects require water, especially during droughts.
    • In 2021, during Alberta’s drought, placing cups of water throughout the greenhouse, saved our biological control program and ensured the survival of essential pollinators.

Other Alternatives

  • If you are not confident in being able to identify the beneficial insects and an aphid population is getting out of control. Another effective strategy you can try is using high-pressure water to blast them off at dawn or dusk
    • This method not only removes aphids but also provides a tasty snack for ground-dwelling predators like Carab Beetles.

Conclusion: Embrace the Balance

Instead of viewing aphids as a nuisance, see them as part of the intricate ecology in your garden. Hopefully this inspires you to delve into the world of these tiny garden inhabitants, learn their life cycles, and create a harmonious ecosystem that promotes biodiversity and effective pest control.