How do I spot common lawn diseases in NB?

Lawn diseases are particularly common in New Brunswick due to our high Maritime humidity and cool, wet springs and falls. The key is learning to identify the most frequent culprits early, since our climate creates perfect conditions for fungal problems that can quickly spread across your lawn.

Snow mold is the most distinctive disease you'll encounter in NB. After snow melts in March or April, you'll see circular patches of matted, grayish-white grass that looks like cotton candy was spread on your lawn. Gray snow mold appears as light gray patches, while pink snow mold has a pinkish tinge. These patches can range from a few inches to several feet across and often have a musty smell. The good news is snow mold rarely kills grass permanently — it just damages the blades, and healthy roots usually recover with proper care.

Brown patch thrives in our humid summers, especially during hot, muggy July nights when temperatures stay above 20°C. Look for circular brown patches that start small but can expand to 2-3 feet across. The telltale sign is a darker brown border around the edge of the patch, often called a "smoke ring." Unlike other diseases, the grass in the center sometimes stays green, creating a "frog-eye" pattern. You'll typically see this on Kentucky bluegrass lawns that are over-fertilized with nitrogen.

Dollar spot appears as small, silver-dollar-sized brown patches scattered across your lawn, particularly in late summer when nights are cool and dew is heavy. Individual grass blades develop tan lesions with reddish-brown borders. In early morning, you might notice white, cobweb-like fungal threads (mycelium) on the affected areas. This disease is more common on fine fescue and stressed lawns that lack nitrogen.

Red thread shows up as irregular reddish-pink patches, especially on perennial ryegrass and fine fescue during cool, moist periods in spring and fall. The distinctive feature is thin, red, thread-like fungal strands extending from the grass blade tips. While it looks alarming, red thread rarely kills grass — it's more of a cosmetic issue that indicates your lawn needs better nutrition.

Powdery mildew appears as a white, powdery coating on grass blades, most commonly in shaded areas with poor air circulation. This is especially problematic in Fredericton's river valley areas and other low-lying spots where humidity lingers. Kentucky bluegrass in shade is particularly susceptible.

Prevention is your best strategy in New Brunswick's disease-friendly climate. Improve air circulation by pruning overhanging branches, water deeply but infrequently (preferably early morning), and avoid over-fertilizing with nitrogen in summer. Core aeration in late August helps reduce moisture retention in our clay soils. Choose disease-resistant grass varieties when overseeding — many newer Kentucky bluegrass cultivars have improved disease resistance.

Most lawn diseases in NB are manageable with proper cultural practices rather than fungicides. However, if you're seeing widespread damage or recurring problems, a professional can help identify the specific disease and recommend targeted treatments that comply with New Brunswick's cosmetic pesticide regulations.

Need help finding a landscaper who specializes in lawn health? New Brunswick Landscaping can match you with local professionals who understand our unique Maritime growing conditions.