What garden pests show up each season in NB?

New Brunswick gardeners face different pest challenges throughout our short but intense growing season, with timing directly tied to soil temperature and our Maritime climate conditions.

Spring Pests (May-June)

Cutworms emerge as soon as soil temperatures hit 10°C in late May, cutting down newly planted seedlings at soil level. These gray-brown caterpillars are particularly destructive to tomatoes, peppers, and other tender transplants. Slugs also become active with spring moisture, leaving silvery trails and chewed holes in hostas, lettuce, and other soft-leaved plants.

Root maggots target brassicas (cabbage, broccoli, radishes) as adults lay eggs around plant bases in late May. The Maritime humidity creates perfect conditions for damping-off fungus, which kills seedlings before they establish. Flea beetles appear with the first warm days, creating tiny shot-holes in brassica leaves.

Early Summer Pests (June-July)

Colorado potato beetles arrive in June, with their distinctive yellow-and-black striped adults and orange egg masses on potato and tomato plants. Cabbage worms (imported cabbage butterfly larvae) start feeding on brassicas, while aphids multiply rapidly in the warm, humid conditions typical of New Brunswick summers.

Tent caterpillars create silk nests in tree branches during June, particularly targeting wild cherry, apple, and other fruit trees. Lily beetles emerge to devastate lilies and fritillarias with their bright red adults and slug-like larvae.

Peak Summer Pests (July-August)

Japanese beetles arrive in July, skeletonizing leaves on roses, grapes, and many perennials. Squash bugs and cucumber beetles attack cucurbits, while tomato hornworms can strip tomato plants overnight. The high humidity promotes spider mites on stressed plants, especially during hot, dry spells.

Earwigs become problematic in August, hiding in mulch during the day and feeding on soft plant tissues at night. Slugs remain active throughout summer in our moist climate, particularly troublesome in shaded areas and during frequent Maritime rain periods.

Late Summer/Fall Pests (August-September)

Fall webworms create unsightly webs at branch tips, different from spring tent caterpillars. Cabbage root flies have a second generation in late summer, attacking fall brassicas. Aphids often surge again in September as plants begin to stress.

Rodent preparation begins in late summer as mice and voles start seeking winter shelter, potentially damaging tree bark and bulbs. Slugs remain active until hard frost, making fall cleanup crucial.

Year-Round Considerations

New Brunswick's freeze-thaw cycles don't eliminate all pests — many overwinter as eggs, pupae, or adults in soil, mulch, or plant debris. Imported pests like emerald ash borer are spreading into the province, requiring monitoring of ash trees.

Integrated pest management works best in our climate: encourage beneficial insects with diverse plantings, use row covers during peak pest periods, and maintain good garden hygiene. Fall cleanup is particularly important since many pests overwinter in garden debris.

Timing treatments to our specific growing season is crucial — beneficial insects are also active during our short summer, so targeted approaches work better than broad-spectrum treatments. Many organic controls work well in our humid climate, while others may wash off during frequent summer rains.

Need help creating a pest-resistant landscape design? New Brunswick Landscaping can connect you with local professionals who understand our unique Maritime growing conditions and pest cycles.