The City is advising residents to inspect their black ash trees for cottony psyllid.
The invasive species is identifiable through curled leaves containing white tufts, followed by yellowing and leaf drop.
Residents can help prevent the outbreak by keeping their ash trees healthy.
This can be done by running a garden hose near the ends of the branches once a month from late June to late August, and fertilizing the surrounding lawn to ensure the tree gets nutrients.
This is the third year Grande Prairie is being affected by cottony psyllid.