Insect Biocontrols
Biological Control, also called Biocontrol, is a component of integrated pest management that uses a natural predator (“agent”) to control a pest species. Both pests and biocontrol agents can be a variety of organisms. Commonly, biocontrol agents are insects, microorganisms or other animals (for example, goats). Pests that are targets for biocontrol are usually insects or weeds.
The City of Saskatoon has been trialing the use of insect biocontrol agents. Insect biocontrols may help control populations of nuisance pests, such as other insects or weeds. Our current programs include biocontrol use for the control of the purple loosestrife weed, the leafy spurge weed, and the red lily leaf beetle.
Purple Loosestrife (Lythrum salicaria)
Purple Loosestrife is a noxious weed that has spread rapidly across North America and is present in nearly every Canadian province. This plant can produce as many as two million seeds in a growing season, which creates dense stands that outcompete native plants for habitat. This reduces nesting sites, shelter, and food for birds and other animals, reducing biodiversity. The plant grows on average to be 60-120 cm tall and averages 1-15 flowering stems.
The Biocontrol Agent: Black-Margined Loosestrife Beetle (Galerucella calmariensis & G. pusilla)
These small orange and black-striped beetles are a natural predator of purple loosestrife. Larval damage to buds and shoots reduces purple loosestrife growth and its ability to flower and seed. Damage to the leaves reduces purple loosestrife's capacity to photosynthesize, increasing overwintering death and producing less vigorous plants which compete less with native plants. These beetles can find new purple loosestrife stands up to 1 km away.
Leafy Spurge (Euphorbia virgata)
Leafy spurge is a noxious weed that has spread rapidly across North America and is present in nearly every Canadian province. It has been known in Saskatchewan since the 1930s. It produces a milky liquid from its stems and flowers that is an irritant and may cause rashes, and it can spread its seeds up to five metres away, where they can remain dormant for up to eight years. The plant reduces nearby native plant growth by releasing toxins into the soil, which only Leafy Spurge can tolerate.
The Biocontrol Agent: Leafy Spurge Flea Beetles (Aphthona spp.)
There are several flea beetle species in the genus Aphthona that are used to control Leafy Spurge. The larvae of these beetles feed on the root system of the weed and this is the most effective stage of control. In adulthood, the beetles, when in high densities, can consume the rest of the weed before it produces seeds. Though the beetle has been proven to be an effective biocontrol agent, it takes many years to establish an effective population.
Red Lily Leaf Beetle (Lilioceris lilii)
The Red Lily Leaf Beetle is an invasive beetle that has been known in North America from 1945 and has rapidly spread across the continent in urban spaces. This beetle feeds on any species of true lily, such as those commonly planted in gardens (Asiatic lilies, Trumpet lilies, etc.). The beetles can fly over long distances, and each female beetle lays between 200-400 eggs per summer, making it a voracious garden pest. It is also a threat to Saskatchewan’s provincial flower, the Western Red Lily.
The Biocontrol Agent: Tetrastichus setifer
This small parasitoid wasp is harmless to humans and cannot sting, but it predates on the larval stage of the red lily leaf beetle. It inserts its ovipositor (egg laying stinger) into the larval stage of the beetle and lays its eggs. The eggs then develop inside the beetle larvae and kill the beetle before it becomes an adult.
