In Maryland, garden pests can wreak havoc on plants, especially in the state’s warm, humid climate. Here’s a quick guide to the 10 most common pests and how to manage them effectively:

• Aphids: Active from March to the first frost, they damage new plant growth. Use water sprays or attract ladybugs to control them.
• Japanese Beetles: Peak in July, skeletonizing leaves. Hand-pick them or use pheromone traps.
• Slugs: Thrive in damp conditions, especially in spring and fall. Use barriers like copper tape or beer traps.
• Snails: Similar to slugs, they attack young plants. Remove hiding spots and use organic baits.
• Cucumber Beetles: Active from April to September, they damage cucumbers and melons. Use row covers and sticky traps.
• Leafhoppers: June to September, they suck sap and spread diseases. Use reflective mulch and insecticidal soap.
• Scale Insects: July to October, they drain plant sap. Prune infested branches and apply horticultural oil.
• Spider Mites: Thrive in hot, dry summers (June–August). Mist plants and introduce predatory mites.
• Thrips: Peak in August, leaving silvery streaks on leaves. Use blue sticky traps and reflective mulch.
• Bagworms: Visible in late summer and fall, they defoliate evergreens. Remove bags by hand and maintain healthy plants.

Key Tip: Regular inspections and early intervention are crucial to protecting your garden. For detailed pest management strategies, read on.

How to Identify Insect Pests in Your Vegetable Garden – CSI …

Maryland Garden Pests: Seasonal Patterns

Understanding when pests are most active can help you time your inspections and treatments effectively. In Maryland, the mild spring weather often brings out soft-bodied pests like aphids, which target new plant shoots. Catching these early can stop small problems from turning into major infestations.

As summer heats up and humidity rises, pests like Japanese beetles and spider mites thrive. When fall approaches and the days grow cooler, pests such as bagworms and scale start preparing to overwinter. These seasonal patterns provide a helpful guide for managing pests throughout the year. Let’s take a closer look at the top ten pests and when they’re most active.

1. Aphids

As spring arrives in Maryland, aphids become one of the first major challenges for gardeners.

These tiny, 1/8-inch pear-shaped insects can be green, yellow, black, or brown and are easily recognized by the small tube-like structures (cornicles) on their backs. They tend to gather on the undersides of leaves and new plant growth, causing several issues: yellowing or distorted leaves, stunted growth, sticky honeydew that leads to sooty mold, and overall plant weakness, making plants more prone to disease.

Aphids are active from March, once temperatures rise above 40°F, and remain a problem until the first frost. Their activity tends to peak in May and June.

Prevention and Management Tips

• Plant dill, fennel, or cilantro to attract natural predators like ladybugs and lacewings.
• Spray plants with a strong jet of water every 2–3 days to dislodge aphids.
• Space plants properly and avoid overusing nitrogen fertilizers to improve airflow and reduce aphid attraction.
• Encourage beneficial insects like ladybugs and lacewings to keep aphid populations in check.

2. Japanese Beetles

Japanese beetles (Popillia japonica) are small, metallic green-and-copper insects about 1/2 inch long. They are notorious for destroying plants like roses, grapes, and fruit trees by eating the leaf tissue and leaving only the veins behind, a process known as skeletonizing. These beetles thrive in Maryland’s humid summers, often causing rapid defoliation in affected plants.

They typically show up in late June, reach their peak activity in July, and remain a problem until the first frost in September. Their summer activity aligns with spider mite outbreaks, making mid-season scouting essential. Inspecting your garden regularly in July can help you spot damage early and protect your plants from severe harm.

Prevention and Management Tips

• Use pheromone traps: Place traps around the edges of your garden to catch adult beetles.
• Hand-pick beetles: In the early morning, beetles are less active, making it easier to remove them by hand.
• Choose resistant plants: Opt for species like magnolias or red maples, which are less appealing to these pests.
• Apply organic sprays: Neem oil or pyrethrin-based sprays can help control beetles when they first appear.
• Focus on soil health: Healthy soil can strengthen plants, making them more resilient to beetle damage.

Once Japanese beetle season winds down, other pests like snails may become active at night, requiring a shift in control methods.

3. Slugs

Slugs are among the most troublesome garden pests in Maryland, especially during wet spring and fall seasons. These soft-bodied creatures, measuring between 1/2 to 4 inches long, are nocturnal feeders. They leave behind telltale silvery slime trails and chew irregular holes in leaves, fruits, and vegetables.

How to Spot Them and Recognize Damage

• Slugs are typically gray, brown, or black.
• They thrive in damp conditions and are most active at night.
• Look for large, uneven holes in plant leaves.
• They often attack tender seedlings and low-growing plants.
• Slime trails on plants and soil are a clear sign of their presence.

When Are They Most Active?

• Early spring (March to May)
• Late summer into fall (August to October)
• After rain or garden watering
• On humid nights when temperatures exceed 50°F

Tips to Prevent and Control Slugs

• Clear away debris, rocks, and boards where slugs like to hide.
• Water your garden in the morning to reduce moisture at night.
• Use barriers like copper tape or diatomaceous earth around plants.
• Set shallow beer traps at soil level to attract and trap slugs.
• Space plants properly to improve air circulation.
• Go slug hunting at night with a flashlight and remove them by hand.
• Use organic slug baits with iron phosphate for effective control.

Rainy weather often leads to an uptick in slug activity, so regular checks are essential in Maryland’s humid conditions. Since slugs and snails often appear together, similar control methods can help manage both pests.

4. Snails

Snails, much like slugs, are nighttime feeders and are easily identified by their spiral shells. They leave behind ragged holes in leaves and noticeable silvery slime trails, often targeting tender seedlings and low-growing plants. Maryland’s humid climate and lush vegetation make it a perfect environment for these pests.

When They’re Most Active

Snails are most active under specific conditions, including:

• Early spring (March–May)
• Late summer through fall (August–October)
• During or after rainfall
• Damp nights with temperatures above 50°F
• Feeding primarily between dusk and dawn

Prevention and Control Methods

To protect your garden, consider these strategies:

• Use crushed eggshells or sand as barriers around vulnerable plants.
• Apply copper tape to pots, raised beds, and tree trunks.
• Eliminate hiding spots like stones, boards, and dense ground cover.
• Water your garden in the morning to reduce nighttime dampness.
• Handpick snails at night with the help of a flashlight.
• Set shallow traps using beer or a yeast-water mixture.
• Use organic iron phosphate baits in high-activity areas.
• Keep a strip of dry soil around garden beds to deter movement.

Garden Impact

Snails can cause noticeable damage, particularly to:

• Young seedlings
• Tender leafy vegetables
• Ripening fruits close to the ground
• Ornamental plants
• Herb gardens

As the season shifts from spring to summer, it’s time to watch for cucumber beetles, which bring their own set of challenges and require different control techniques.

5. Cucumber Beetles

As summer begins, cucumber beetles make their appearance, targeting cucumber, melon, and squash plants. If not managed, these pests can severely impact crop production.

How to Spot Them

Maryland is home to two types of adult cucumber beetles, each about ¼″ long. The striped beetle is yellow-green with three black stripes, while the spotted variety is yellow-green with twelve black spots. Their larvae live underground, feeding on plant roots.

The Damage They Cause

Cucumber beetles chew on leaves, flowers, stems, and fruit. They also spread diseases like bacterial wilt and mosaic viruses. Larvae can damage roots and seedlings, leaving scars that affect plant growth.

When They’re Active

These pests are most active from mid-April to early May, with peak activity in late June through July and another surge in late August to September. As late summer temperatures rise, keep an eye out for leafhoppers too.

How to Prevent and Control Them

• Rotate crops every year to disrupt their life cycle.
• Cover plants with row covers until they start flowering.
• Space plants to improve airflow and remove plant debris.
• Use yellow sticky traps and hand-pick beetles in the early morning.
• Plant marigolds or nasturtiums nearby to deter them.
• Apply a layer of kaolin clay to protect plants.
• Attract natural predators like ground beetles and parasitic wasps.
• Water plants at the soil level to minimize moisture on leaves.

6. Leafhoppers

Keep an eye out for leafhoppers from June through early fall. These tiny insects, which thrive in the heat of late summer, can harm plants by sucking sap and stunting their growth.

Leafhoppers (Cicadellidae) are small, wedge-shaped bugs, typically 1/8″–1/4″ long, and come in shades of green, brown, or yellow. In Maryland gardens, they are most active from June through September, with their peak overlapping cucumber beetles. This makes it essential to scout for both pests at the same time.

Damage and Impact

Leafhoppers pierce leaves to feed on sap, leaving behind stippling – small white or yellow spots. They also spread diseases like aster yellows, which can cause plants to grow poorly and develop yellowed, curled leaves.

Prevention and Management Tips

• Use row covers early in the season to block infestations.
• Lay reflective mulch around plants to confuse leafhoppers.
• Treat affected plants with insecticidal soap, focusing on the undersides of leaves.
• Encourage natural predators like lacewings and parasitic wasps.
• Remove weeds from garden edges to eliminate alternative host plants.
• Check plants weekly during peak activity (July-August).

Leafhoppers often persist alongside cucumber beetles and spider mites until the first frost. Taking action now can also help reduce the number of overwintering pests.

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7. Scale Insects

Scale insects are tiny pests (about 1/8 to 1/4 inch long) that show up in late summer and can stick around through winter. They feed on plant sap and develop a hard shell or waxy coating as they mature, making them look like small bumps on stems, branches, or leaves.

Similar to aphids and leafhoppers, scale insects damage plants by draining sap and encouraging the growth of sooty mold – a black fungus that forms on their sugary waste, known as honeydew. Infested plants often show yellowing leaves, slowed growth, and even branch dieback. In Maryland, both armored and soft scale insects are most active from July to October, though they can survive all year on evergreen plants.

Prevention and Control Methods

• Prune and discard heavily infested branches during the plant’s dormant winter period.
• Apply horticultural oil in late winter before new growth begins.
• Use a soft brush and soapy water to gently scrub scales off stems.
• Attract natural predators like ladybugs and parasitic wasps to your garden.
• Inspect plants monthly for early signs of scale activity.
• Treat young "crawler" stages with insecticidal soap before they form their protective shells.

Scale insects often become noticeable around the same time spider mites surge in late summer, so thorough plant inspections during this season are especially important.

8. Spider Mites

Spider mites become a common issue during Maryland’s hot, dry summers. These tiny pests, about 1/50" long, thrive in such conditions and are often spotted alongside scale insects later in the season. While they’re hard to see with the naked eye, their fine webbing on leaves and stems is a clear sign of their presence.

When They’re Most Active

Spider mites are most active under the following conditions:

• Temperatures above 85°F
• Low humidity
• Drought-stressed plants
• Peak hours in the late afternoon
• From June through August

Damage and Impact

Spider mites can cause noticeable damage, including:

• Tiny yellow spots (stippling) on leaves
• Webbing between leaves and along stems
• Leaves turning yellow, bronze, or brown
• Premature leaf drop
• Slowed plant growth

Prevention and Management Tips

Here are some practical ways to manage spider mites:

• Mist plants regularly to raise humidity.
• Spray the undersides of leaves with water every few days.
• Check plants weekly, especially during hot, dry weather.
• Introduce predatory mites early in the season.
• Ensure plants are spaced properly for better air circulation.
• Use insecticidal soaps or neem oil at the first sign of mites.
• Avoid over-fertilizing with nitrogen, as it can attract mites.

Spider mites can severely stress plants during the peak of summer. As temperatures drop, their activity usually decreases, but be prepared for thrips, which often emerge next. Keep monitoring your plants to stay ahead of pest issues.

9. Thrips

After the dry-weather outbreaks of spider mites, thrips often emerge as the next sap-feeding issue in late summer. These slender insects, part of the Thysanoptera order, feed by puncturing plant leaves and sucking out their contents.

When They’re Most Active

Thrips tend to thrive:

• From June to September, with activity peaking in August
• During hot, dry weather
• In the mid-afternoon when temperatures are at their highest
• After spider mite populations have started to drop

Signs of Damage

These tiny pests, measuring 1/16–1/8″ long, leave behind unmistakable damage:

• Silvery streaks and patches on leaves
• Black spots of fecal matter on leaf surfaces
• Leaves that curl or show distorted growth
• Stunted flowers
• Scarring on fruits and vegetables
• Spread of plant viruses like tomato spotted wilt

How to Manage and Prevent Thrips

To keep thrips under control, try these methods:

• Set up blue sticky traps to monitor and capture adult thrips
• Clear away weeds and plant debris where they might hide
• Release natural predators like minute pirate bugs or lacewings
• Use insecticidal soap, focusing on the undersides of leaves
• Lay down reflective mulch to confuse and deter them
• Ensure plants are spaced properly to allow better air circulation

As temperatures cool, thrips activity will decrease, but it’s a good idea to keep an eye out for bagworm egg masses in the fall. Regular monitoring can help you catch infestations early, limit virus spread, and minimize damage to your plants.

10. Bagworms

As summer winds down and fall approaches, bagworms become visible on evergreens throughout Maryland.

How to Spot Them

Bagworms create silk-and-foliage bags measuring 1.5–2 inches, which dangle from branches and resemble tiny pinecones. Male bagworms emerge as small, clear-winged moths, while females stay inside their bags.

The Damage They Cause

Bagworms feed on plants like juniper, arborvitae, spruce, cedar, pine, and some shrubs. Their feeding can strip needles and leaves, leaving behind brown patches or even completely defoliated branches. In severe cases, branches may die.

When They’re Active in Maryland

• June–August: Larvae actively feed during this time.
• Late August–September: Larvae create overwintering bags.
• May: Eggs hatch after overwintering in the bags.

How to Manage and Prevent Bagworms

• Remove Bags by Hand
  Collect and destroy the bags during winter or early spring to stop larvae from emerging.
• Maintain Healthy Plants
  Proper spacing, regular pruning, and consistent watering can help plants resist infestations.
• Seek Professional Help
  Companies like Pro Landscapes MD offer tree trimming and insecticide treatments to address bagworm issues effectively ^[1].

Regular inspections, especially in early summer when larvae are still small, can help prevent serious damage.

^[1] Pro Landscapes MD provides landscaping services, including tree care and treatment options for managing bagworm infestations.

Garden Pest Reference Chart

For a quick overview of common Maryland garden pests, including their favorite plants, damage indicators, and peak activity times, check out our detailed pest management guide. Need personalized help? Contact Pro Landscapes MD for expert advice tailored to your garden.

Getting Help with Garden Pests

When your own pest control efforts and the pest chart fall short, Pro Landscapes MD can step in with expert pest-management solutions provided by their certified horticulturists.

What They Offer:

• Landscape design and installation with water-saving and environmentally friendly techniques
• Comprehensive garden and tree care, including planting, pruning, and seasonal upkeep
• Regular maintenance plans to identify and address pests before they become a problem

Operating in central Maryland, Pro Landscapes MD provides free consultations to help you create pest-resistant landscapes. Reach out to schedule your complimentary consultation today.

Conclusion

Knowing Maryland’s common pests and how to prevent them is key to keeping your garden healthy. Successful pest control relies on spotting issues early, regular maintenance, and expert help to stop infestations from coming back and to keep your plants growing strong. Pro Landscapes MD’s team of certified horticulturists uses native plants, tailored drainage solutions, and eco-friendly methods to design gardens that naturally deter pests. Reach out to Pro Landscapes MD for a consultation to keep your garden thriving and pest-free all year.

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