Calgary streets looked like a syrupy Stampede breakfast as sidewalks and cars were coated in a shiny and sticky coating courtesy of a surge in the aphid population this summer.
The summer of 2024 has seen lots of rain, a nice relief from the water restrictions but it also makes for ideal conditions for insects to multiply. Calgary has been seeing a higher than normal amount of aphids as a result.
“We’ve had cooler, moister weather, for the most part. That helps perpetuate their cycle and they can grow,” said John Swann, head taxonomist for ABI Environmental Services who specialize in entomology.
Aphids feed on the sap produced by plants but only use a very small amount of the nutritional value with the rest being excreted as honeydew, said Swann. Usually honeydew wouldn’t be as noticeable but when thousands of aphids are living on one tree, the excrement coats anything below.
“It was the strangest thing the other morning. I walk my dog the same route through Lindsay Park every morning, and yesterday morning it really seemed like this phenomenon had exploded over night. Everyone in the park, was squelching as their shoes stuck to the pathways. I had to scrub down my Jack Russell’s paws when I got got home as there was so much crap stuck to them,” said Calgary resident Lee Henderson.
Henderson had worked as a Rocky Mountain guide for 20 years and said he had never seen anything like what he saw that morning.
“My hat is also ruined from being covered in the honeydew, I didn’t know I was being dripped on from above until I took it off,” said Henderson.
“Think of ladybugs as sort of the wolves of the insect world. They’re actually feeding on those little aphids, so there are beneficial insects, you want those around,”
JOHN Swann
Swann said that aphids can also alternate between sexual and asexual reproduction through parthenogenesis. This means that female aphids can essentially create clones of themselves through the development of unfertilized eggs.
“Think about how suddenly one female can just keep pumping out progeny that are genetically identical to her and just keep going. That often happens until the fall, at which point they reproduce sexually with males. So these populations can grow incredibly quickly,” said Swann.
Aside from the slightly messy and inconvenient honeydew, aphids do very little harm to plants if any, and are the food source for predatory insects like ladybugs. Ants also protect and farm aphids in order to eat the honeydew they produce.
“Think of ladybugs as sort of the wolves of the insect world. They’re actually feeding on those little aphids, so there are beneficial insects, you want those around,” said Swann.
Aphids may not kill your plants but according to Swann, they do have a chance of spreading plant viruses and slowing fruit growth by eating the leaves.
“To treat them it’s common to take your garden hose and sprayer, which we can’t use in Calgary right now, and just spray the plants to wash them off. This can be very effective, but we can’t do that at the moment,” said Swann.
Calgary is still currently sitting at Stage 3 water restrictions which doesn’t allow for watering from a hose. This is hopefully changing on Thursday, July 18 with the city ramping up the water being fed through the repaired water main.
There are other solutions to using a hose to get rid of unwanted aphids in a home garden like sprinkling Diatomaceous Earth on them, or spraying a solution of Safer’s Insecticidal Soap.
“Aphids tend to have a waxy sort of secretion on their body that protects them from drying out. And both Diatomaceous Earth and Safer’s Soap get rid of that waxy layer and the aphids just shrivel up and die,” said Swann.
With the heat wave still going for at least another week, this problem may disappear on its own unless moisture from thunderstorms keeps the conditions just right for the little green guys.