July Insect Checklist

CHECKLIST OF COMMON INSECT-RELATED EVENTS
– Metro Denver/Boulder Area

This is a generalized checklist of when some of the more important insect-related events tend to occur in the Central, South, and East Counties areas. Year-to-year variations are considerable and this should only be used as a guideline to anticipate and help recognize common insect occurrences.

Early July

Household Insects

Strawberry root weevils: Migrations into homes accelerate.
Sun spiders (wind scorpions): Peak period of indoor migrations.

Tree/Shrub Insects

Peachtree borer: Egg-laying typically begins. Preventive sprays should be made at this time to kill newly hatching larvae.
Elm leaf beetle: First-generation larvae become full-grown and move down the trunk to pupate.
Black vine weevil: Adult leaf notching injuries are obvious on euonymus and rhododendron.
Leaf curling aphids: Most species have departed from overwintering host trees and shrubs.
Cooley spruce gall adelgids: Peak period of emergence from galls and migration to Douglas-fir alternate host.
Pinyon pitch mass borer: Adult emergence continues and egg-laying begins.
Codling moth: Flights and egg-laying of the second, most damaging, new generation often begins at this time.
Leafcutter bees: Characteristic cut leaf injury begins to appear on rose, lilac, and other susceptible hosts.
Apple maggot: Expect the emergence of adult flies and the onset of egg-laying. Monitor flights with sticky traps.

Garden Insects

Mexican bean beetle: Larvae begin to damage beans.
Colorado potato beetle: Peak period of larval injury. End of the first generation.
Tobacco budworm: Early evidence of injury to flowers may be present.

Lawns

Sod webworms: Watch for damage to turfgrasses by the second-generation larvae.

Miscellaneous

Honey bee swarms: This is commonly a time for peaks in swarming on sunny afternoons.

Late July

Tree/Shrub Insects

Codling moth: Second-generation continues to lay eggs. Monitor flights with pheromone traps.
Elm leaf beetle: Second-generation egg-laying and hatching often occur in late July.
Cooley spruce gall: Abandoned galls become dry and very conspicuous.
Pearslug: Larvae damage plum, cotoneaster.
Elm aphids: Stages on leaves excrete large amounts of honeydew.

Garden Insects

Tomato hornworms: Peak damage by larvae occurs over the next month.
Potato/tomato psyllid: Symptoms may begin to appear on potatoes and tomatoes.
Mexican bean beetle: Larvae begin to damage beans.


Concerned about your lawn or tree health?
Call us at 303-806-TREE or Click here to schedule your free plant health care consultation now!


SEASONAL CHECKLIST OF SOME COMMON INSECT-RELATED EVENTS
– ARAPAHOE/DOUGLAS/ELBERT COUNTIES

Early July

Household Insects

Strawberry root weevils: Migrations into homes accelerate.
Sun spiders/Windscorpions: Migrations into homes often peak around this time.

Tree/Shrub Insects

Peachtree borer: Egg-laying typically begins. Preventive sprays should be made at this time to kill newly hatching larvae.
Elm leaf beetle: First-generation larvae become full-grown and move down the trunk to pupate.
Black vine weevil: Adult leaf notching injuries are obvious on euonymus and rhododendron.
Leaf curling aphids: Most species have departed from overwintering host trees and shrubs.
Douglas-fir tussock moth: Typical peak period of injury. Monitor infested trees.
Cooley spruce gall adelgids: Peak period of emergence from galls and migration to Douglas-fir alternate host.
Pinyon pitch mass borer: Adult emergence continues and egg-laying begins.
Mountain pine beetle: Adult emergence usually begins.
Leafcutter bees: Characteristic cut leaf injury begins to appear on rose, lilac, and other susceptible hosts.

Garden Insects

Mexican bean beetle: Larvae begin to damage beans.
Tobacco budworm: Early evidence of injury to flowers may be present.
Grasshoppers: Egg egg largely completed. The optimum time for treatment.

Lawns

Sod webworms: Watch for damage to turfgrasses by the second-generation larvae.
Ant swarms: Winged ants are forced out of colonies during warm afternoons following rainfall events

Late July

Tree/Shrub Insects

Codling moth: Second, and most damaging, generation begins to lay eggs.
Elm leaf beetle: Second-generation egg laying and hatching often occur in late July.
Sawflies: Neodiprion autumnal may cause damage peak in midsummer.
Cooley spruce gall: Abandoned galls become dry and very conspicuous.
Pearslug: Larvae damage plum, cotoneaster.
Elm aphids: Stages on leaves excrete large amounts of honeydew.

Garden Insects

Tomato hornworms: Peak damage by larvae occurs over the next month.
Potato/tomato psyllid: Symptoms may begin to appear on potatoes and tomatoes.
Grasshoppers: Damage accelerates over the next month.
Mexican bean beetle: Larvae begin to damage beans.
European paper wasp: Colonies start to increase greatly in size and foraging adults are commonly seen.


Concerned about your lawn or tree health?
Call us at 303-806-TREE or Click here to schedule your free plant health care consultation now!

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