March Colorado Insect checklist of some common insect-related events – Denver metro and Boulder, Denver South, and East
This is a generalized checklist of when some of the more important insect-related events tend to occur in our area. Year-to-year variations are considerable – this should be used as a guideline to anticipate and help recognize common insect occurrences.
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DENVER METRO & BOULDER
Early March
Household Insects
Boxelder bugs, cluster flies: Overwintered adults become active in and around homes.
Clover mites: Migrations of mites from lawns into buildings may begin at this time, during warm days
Winged termites: Winged reproductive stages continue to swarm in late winter.
Firewood insects: Bark beetles and wood borers emerge from stored wood in homes.
Ants: Foraging by field ants for sweet materials intensifies in homes.
Trees/Shrubs
Poplar twig gall fly: Larvae begin to leave galls and pupate in the soil at the base of trees.
Oystershell scale: Scrape scales with eggs off limbs of aspen, ash, and other host plants.
Ips beetles: Ips (engraver) beetles may be active during warm periods. Spruce and pines in high-risk sites may need protection.
Lawns
Clover mites: Mites are actively feeding on lawns near buildings and shrubs during warm days.
Nightcrawlers: Tunneling activities during spring can create lumpy lawns.
Vole injury: Tunneling injuries in lawns and girdling of shrubs may be evident as snow melts.
Late March
Household/Miscellaneous
Flickers: Males are actively drumming on buildings and defending territories during mating season.
Ants, clover mites: Movements indoors continue.
Trees/Shrubs
Poplar twig gall fly: Larvae continue to leave galls and pupate in the soil at the base of trees.
Dormant oils: Many insects that winter on plants can be controlled with dormant applications of
horticultural oils.
Pinyon needle scale: Females produce cottony egg sacks on branches and trunks.
Ips beetles: Ips (engraver) beetles may be active during warm periods. Spruce and pines in high-risk sites may need protection.
Southwestern pine tip moth: Adults begin to emerge from pupae at the base of trees.
Spider mites on juniper: Spring populations may begin to increase; monitor plants.
DENVER SOUTH AND EAST
Early March
Household Insects
Boxelder bugs, conifer seed bugs, cluster flies: Overwintered adults become active in and around homes.
Clover mites: Migrations of mites from lawns into buildings may begin at this time, during warm days
Firewood insects: Bark beetles and wood borers emerge from stored wood in homes.
Subterranean termites: Winged adults of the arid land subterranean termite fly in late winter.
Trees/Shrubs
Oystershell scale: Scrape scales with eggs off limbs of aspen, ash, and other host plants.
Late March
Household/Miscellaneous
Flickers: Males are actively drumming on buildings and defending territories during mating season.
Swallow Bugs: Overwintered swallow bugs become active in anticipating returning migrant birds and bite humans.
Millipedes: Nuisance movements into homes occurs following wet weather.
Ants: Field ants forage in homes for sweet materials.
Carpet beetles: Some species of carpet beetles are noticeable in spring when they transform into adults.
Trees/Shrubs
Poplar twig gall fly: Larvae begin to leave galls and pupate in the soil at the base of trees.
Dormant oils: Many insects that winter on plants can be controlled with dormant applications of horticultural oils.
Ips beetles: Ips (engraver) beetles may be active during warm periods. Recently transplanted pines may need protection.
Southwestern pine tip moth: Adults begin to emerge from pupae at the base of trees.
Spider mites on conifers: Spring activity of spider mites on junipers, pines, arborvitae, and spruce increase during spring.
Lawns
Clover mites: Mites are actively feeding on lawns near buildings and shrubs during warm days.
Nightcrawlers: Tunneling activities during spring can create lumpy lawns.
Vole injury: Tunneling injuries in lawns and girdling of shrubs may be evident as snow melts.
