Track pest insect activity on trees and shrubs in Massachusetts seasonally with our monthly insect almanacs. Pest life cycles vary throughout the growing season and so do professional options for management. Consider this pest itinerary when planning ahead.
Not all managed landscapes in Massachusetts will have every pest mentioned present. Alternatively, some pests that are commonly found through monitoring efforts may not be included here.
Be aware that, in the end, insects often do not follow calendars! Dates of pest activity are not exact and are based on historical observations and general trends. Pest presence should be confirmed via site-specific monitoring practices. Activity at a given location may vary depending on local climate factors and fluctuations due to climate change.
Look to UMass Extension’s Landscape Message for growing degree day (GDD) reports and current pest activity.
This resource is for educational purposes only – always rely on current monitoring to make actual management decisions.
March April May June July August September
March
Click on each picture for a description.
1
Still frozen? It might not look like it, but insects will be awakening soon. Learn more and start planning with the Professional Insect & Mite Guide.
5
Itching to go outside? Overwintering insect eggs can be removed at this time. Search for bagworm bags, viburnum leaf beetle eggs, eastern and forest tent caterpillar egg masses.
11
Learn more about human assisted movement of wood boring insects like emerald ash borer and Asian longhorned beetle.
15
Curl up with a warm cup and check out some short educational videos about insects with UMass Extension’s InsectXaminer.
17
Spotted lanternfly overwinters as an egg mass on many flat surfaces. Search for, report and scrape off egg masses.
21
Balsam twig aphid eggs hatch between 30-120 GDD, in April and May. Check your notes from last year and start planning management.
26
White pine weevil adults overwinter and become active at 7 GDD. Monitor closely if managing the adults.
31
If winter moth is problematic in your area this year, learn more to be prepared. Egg hatch at 20-50 GDD, late March through mid-April.
April
Click on each picture for a description.
1
Woolly aphids such as woolly apple and woolly elm (both on elm; Ulmus spp.) and woolly beech leaf aphid may be very noticeable in the spring but not harmful to their hosts.
5
Monitor viburnum for distorted, curling leaves created by the feeding of snowball aphids or similar insects. Manage early.
11
Pine bark adelgid is a native insect active in the spring which makes pines (Pinus spp.) appear as if covered in snow.
15
Lecanium scales overwinter on twigs and begin feeding again in the spring (April-May). Egg laying and much honeydew can occur.
17
Check pines (Pinus spp.) for hatching European pine sawfly or other pine sawfly eggs. Larvae quickly defoliate plants; scout late April – June!
21
Boxwood leafminer start pupation in late April. Adults emerge by mid-May, leaving shed pupal skins stuck to leaves (350-600 GDDs).
26
Overwintered eastern tent caterpillar eggs will hatch as wild cherry leaves open (approximately 90-190 GDDs).
30
Prepare for cankerworm egg hatch by mid-May, with caterpillar feeding through roughly the end of June (start 115-290 GDDs).
May
Click on each picture for a description.
1
Monitor elm (Ulmus spp.) leaves for zig-zagged feeding damage from the larvae of the introduced elm zigzag sawfly. Report if found!
5
Euonymus caterpillars on European spindle tree (Euonymus europaeus) and others can be prolific by the end of the month. Look for caterpillars and silken webs.
11
Spotted lanternfly eggs hatch at approximately this time. Look for first instar nymphs (immatures) that are black with white spots. Report!
15
Hydrangea leaftier “envelopes” or tied together leaves may be obvious on smooth hydrangea (Hydrangea arborescens) and cultivars.
17
Magnolia scale may become more noticeable on their namesake hosts over the next month or so. Active at least through August.
21
Oystershell scale egg hatch can occur through approximately mid-June. Monitor host twigs for small, mussel-shaped insects.
26
Scout privet (Ligustrum spp.) and other hosts for privet thrips activity. Leaves will appear discolored with grayish speckles or chlorosis.
30
Fletcher scales should be noticeable if present on yew (Taxus spp.) and laying 500-600 eggs beneath their bodies in late-May to early-June.
June
Click on each picture for a description.
1
Lace bug activity on Rhododendron spp. should be monitored, especially if plants have a history of lace bug issues. Search leaf undersides.
5
White-spotted sawyers are convincing native look-alikes of Asian longhorned beetle (ALB). Sawyers are out now, ALB usually after July 1.
11
Box tree moth caterpillars have likely fed on boxwoods, pupated and subsequent multiple generations will be active. Report!
15
Fall webworm eggs can hatch by late June or early July, with webbed branches close behind. Monitor specimen trees early.
17
Bagworm eggs hatch and caterpillars defoliate their hosts between 600-900 GDDs. Scout plants now before feeding is severe.
21
Viburnum leaf beetle larval feeding damage is very noticeable if eggs were not removed in March. Expect adults by mid-July.
26
Twospotted spider mite is a pest of many trees and shrubs. They prefer hot, dry conditions and populations can increase in the summer.
30
Japanese beetle adults are typically active by the end of June throughout August. Adults will skeletonize the leaves of many ornamentals.
July
Click on each picture for a description.
1
Asian longhorned beetle adults have historically started emerging by July 1st in Massachusetts. Report beetles or damage to maple!
5
Dogwood sawfly adults can emerge and lay eggs from May through July. Scout for larvae feeding on the leaves of dogwood (Cornus spp.).
11
Mimosa webworm feeding damage can be noticeable by July. Look for bronzed leaves and webbing in honeylocust and mimosa.
15
Pear sawfly larvae are sluglike and feed on the foliage of cotoneaster, hawthorn, and fruit trees. Scout for in July, becoming abundant in August and September.
17
Tuliptree aphid can be abundant, creating much honeydew that is then coated in sooty mold. Hungry ladybeetles may be nearby!
21
Azalea leafminer may be mining and tying the leaves of azalea with silk. Leaves may be brown in patches. Rake up fallen leaves, which may disrupt the overwintering life stage.
26
European hornets are large and may be confused for the northern giant hornet. European hornets strip bark from certain trees and shrubs. Report suspicious hornets!
30
Spotted lanternfly adults are typically present by the end of July or the beginning of August until the first hard frost. Please report them!
August
Click on each picture for a description.
1
Eastern spruce gall adelgid galls may still be green, containing insects. Prune out of ornamentals before insects emerge.
5
Hickory and other tussock moth species may be seen wandering landscapes. Avoid touching hairy caterpillars or their cocoons without prior ID. Some cause contact dermatitis.
11
Oak skeletonizer feeding is noticeable. This native species can occasionally outbreak. Rake fallen leaves to remove cocoons.
15
August is tree check month! Check maples for evidence of Asian longhorned beetle damage including round 3/8’’ exit holes. Report!
17
Mature red-humped caterpillars occasionally feed on the leaves of ornamental trees and shrubs. Native insects, they may feed through September.
21
Magnolia scale crawlers may be present by late August. Adult females are large, white and conspicuous at this time.
26
Spotted lanternfly adults are present and laying eggs in masses until the first hard frost in MA. Take photos and report!
30
Don’t like sharing space with overwintering insects inside? Now is the time to repair even tiny gaps in windows, doors or other entry points.
September
Click on each picture for a description.
1
Locust borer adult beetles may be active until the first frost. Adults feed on goldenrod, then lay eggs on black locust where larvae bore the wood.
5
Monitor the health of pitch pine in Massachusetts. Southern pine beetle has migrated north with climate change. Take photos & report!
11
White-marked tussock moth caterpillars may still be encountered. Avoid touching – hairs can cause allergic reactions.
15
Dogwood borer adult moths may continue their flights through September. Avoid wounding susceptible hosts which provides entry.
17
Take a minute to remember that most insects are critical members of their ecosystems. Less than 1% of the estimated 2-30 million insect species on planet earth are pests.
21
Encourage clients to avoid moving firewood long distances this year. Buy or source wood locally. Help reduce the risk of moving wood boring insects.
26
Make a plan to learn more about beneficial insects, natural enemies and pollinators! They are as important to recognize as the pests!
30
Review notes from managing insects this year. What worked? What didn’t? What new plans will you need in the next growing season?