Insects: Life and Death on the City’s Foliage

Text by Janis Ringuette

Photos by Norm Ringuette

Dr. Michelle Gorman insect study

Dr. Michelle Gorman scrutinizes an insect under her microscope, one of many thousands--dead and alive--which have passed through her small upstairs office in the Parks Maintenance building on Cook Street. As Integrated Pest Management (IPM) Coordinator for the City of Victoria's Parks Department, part of Gorman's job is to stop invasive insect pests in their tracks using environmentally friendly strategies.

Monitoring is a never-ending task in managing established insect pests because those cannot be eradicated, only controlled. Many insect pests, like invasive plants, are foreign invaders introduced (often accidentally) from another region of the world; newly arrived alien insects can explode in numbers because natural checks have not had time to evolve. “A native insect would have it's own native predators and parasites to keep its populations in check,” Gorman explained. Though native species generally reach a balance as they evolve together over time, native insect populations can explode, too, when conditions change.

When the numbers of insect pests on the city’s foliage become too numerous, Gorman marshals insect predators to kill and eat them. That's why, in July, a canvas bag full of live aphid-eating ladybugs was stored in her small office refrigerator next to the juice, yogurt and sandwiches.

Ladybugs must be kept cold until placed in position at the city’s aphid hot-spots because, Gorman says, "A warm ladybug is an active ladybug." To prepare for transportation to the release sites on downtown trees under siege, Gorman moved handfuls of ladybugs, shown below left, to small tupperware containers (center photo), which are placed on ice blocks in an insulated carry box.

Ladybugs in a refrigerated bag     Tupperware container for ladybug distribution    Ladybug larvae do most aphid eating

To encourage ladybugs to remain where they are placed, Parks Department workers Carla Parkes and Kathy Tardiff used trigger-spray water bottles to squirt a line of water leading up selected downtown street trees on Broughton, Blanchard and Fort before carefully placing the ladybugs. “Water is the key to ladybug happiness,” Gorman explained. “They are thirsty from being cold." When water is provided, ladybugs climb up to the crowns of the trees, mate and lay eggs which hatch into ugly, voracious larvae like the one above right. “Larvae eat full time and consume many more aphids than the adults,” according to Gorman.

Sticky card traps tiny Fungus Gnats and Thrips

In the Beacon Hill Park nursery, Gorman checks the number and insect species adhering to a "yellow sticky trap," shown here. There is about a two week lag before the “biologicals” placed on plants to combat pests become effective, so she checks the two-sided sticky cards weekly to stay on top of possible infestations. A low number of pests can be picked off plants by hand, she explained, plucking aphids from a geranium stem and squishing them between her fingers. Another low-tech solution is spraying a soap solution on leaves. However, if large numbers of insect pests such as tiny fungus gnats and thrips are found trapped on the sticky cards, Gorman selects the right tiny assassin to place in the infested plant flats. She orders a supply of a mite that eats fungus gnats and a second mite that eats thrips.

Dr. Gorman inspecting a Para-Strip    Closeup of a Para-Strip containing wasps

To eradicate whitefly, the biological weapon of choice is a parasite. Gorman examines a small tag called a “Para-Strip" hanging from a fuchsia, above left. When the Para-Strip is placed on the plant, the small circle at the bottom, visible in the closeup to the right, is packed with tiny wasps called Encarsia formosa. The wasps emerge to lay their eggs on the problem whitefly.

Another important part of Gorman’s job is to inspect all new plant material brought into the nursery or other city properties. Purchased trees usually arrive with root balls wrapped in burlap; she pulls back the covering and has a close look at the soil. All new plant flats and shrubs are inspected and those with infestations returned to the supplier. On July 22, for example, just-arrived small Poinsettias were checked for whitefly before being planted out in the nursery.

Garry oak leaves attacked    Maple leaf riddled with holes    Caterpillar winter moth

Millions of oak, maple and cherry tree leaves in Beacon Hill Park and around the region were full of holes this summer. In the far left photo, a healthy, intact Garry oak leaf is shown next to a much-chewed leaf. A heavily damaged Big-leaf maple leaf is shown in the middle photo. According to Dr. Michelle Gorman, the green inch-worm larvae of the winter moth (Operophtera brumata), shown far right, is responsible for the damage. (Larva photo courtesy of Fabio Stergulc, University of Udine,

“Winter moth was introduced from Europe to Nova Scotia in the 1950's and into BC in the late 1960's...," she explained. "Following research conducted on the East Coast, the Pacific Forestry Center on Burnside Road collaborated with the University of Victoria to conduct a study on releasing parasites and predators that occur in Europe to keep this insect in check.” The parasite and predator release that took place in the late 1970's was effective in keeping winter moth in check until the last few years.

Collecting winter moths

Research is currently being conducted in Victoria parks in an effort to understand why winter moth populations have increased. In the photo above, researchers knocked larvae off a Summit Park Garry oak onto a tarp so they could be collected and analyzed. Gorman explained: “Nicholas Conder, working for Dr. Imre Otvos at the Pacific Forestry Research Centre, is conducting research on the winter moth parasite relationship in our parks this year as part of a continuing study from last year.” (City of Victoria photo)