Spring Pest Guide for North Bay California

Termite Swarm Season — The Most Important Spring Pest Event

Subterranean termite swarm season peaks in the North Bay from January through April — triggered by winter rain events that signal to mature colonies that conditions are right to produce reproductive swarmers. Drywood termite swarmers begin appearing in some years as early as April, with peak activity in August–October.

If you see large numbers of winged insects emerging from walls, ceilings, or soil near your foundation after a rain event in spring, you are almost certainly witnessing a termite swarm. This is the most important early warning sign that a colony is established and mature enough to reproduce — and an immediate call for professional inspection is warranted.

Spring Argentine Ant Expansion

Argentine ant super-colonies expand dramatically in spring as warming temperatures and the first flush of vegetation drive forager numbers up. Spring is when North Bay homeowners most commonly notice ant trails entering the structure — through foundation gaps, under door thresholds, around plumbing penetrations, and along utility conduit. Professional perimeter treatment applied in early spring intercepts expanding colonies before they establish indoor foraging routes.

Bee Swarms

Honey bee swarms are common in the North Bay from March through May as established hive colonies split and a new queen departs with approximately half the workers to find a new nesting location. Swarms appear as dense clusters of bees on a branch, fence, or building surface — typically for 24–72 hours while scouts locate a permanent nest site. Most swarms are not aggressive and will move on within a day or two. If a swarm settles inside a wall cavity or attic, however, professional removal is required.

What to Do in Spring

Spring pest priorities for North Bay homeowners:

• Schedule your annual termite inspection if it has not been done in the past 12 months
• Apply perimeter ant treatment in March–April before colonies are fully established
• Inspect all exterior vents and roofline gaps for potential yellowjacket queen nest sites
• Examine fruit trees and ornamental trees for signs of roof rat activity as spring fruit begins to develop
• Address any plumbing leaks or drainage issues revealed by winter rains — moisture drives multiple spring pest pressures

Frequently Asked Questions