Identifying Common Spring and Summer Tree Insects (Pests)

Identifying Common Spring and Summer Tree Insects (Pests)

We’re weeks into the growing season, and our trees are happy to show off their fresh appearance: a full, blooming canopy, sprouting flowers and fruits and—wait, are those curling leaves?

Damage to tree leaves and stems is often the first sign of a bigger tree problem, possibly an insect infestation.

If you’ve seen something odd on your tree, find out what the problem is. Use our checklist below to pinpoint what insect could be damaging your trees and how to stop it.

Symptoms: Leaf curling, twig dieback, a sugary substance called “honeydew,” black, sooty mold and stunted growth

  • What insect is damaging my tree: Aphids, the resident “plant lice”

  • What do aphids do: They feed on tree leaves and stems, prevent proper nutrient and sunlight intake and cause premature leaf drop.

  • How to control aphids on trees: Stop aphids using horticultural soap treatments or insecticides.

  • When to control aphids: Talk to your arborist as soon as you spot symptoms.

Symptoms: Chewed, ragged-looking leaves that fall prematurely in spring 

  • What insect is damaging my tree: Cankerworms, the hungry, hungry caterpillar

  • What do cankerworms do: They eat away at leaves, stripping the tree of nutrients.

  • Most common tree victims of cankerworms: Elm, oak, apple, maple, linden, beech, cherry, hickory and ash

  • How to control cankerworms: Apply a pesticide in spring to remove cankerworms. Then prevent in the fall with an insecticidal tree band.

  • When to treat cankerworms: Control this pest in spring and focus on cankerworm prevention in fall.

Symptoms: Chunks of leaves chewed down to the veins, browning leaves around the top of the tree canopy and leaves falling in summer

  • What insect is damaging my tree: The flying, feeding Japanese beetle

  • What do Japanese beetles do: They feed on tree leaves in warm, sunny weather. This tree pest often eats the entire leaf, leaving behind only the skeleton.

  • Most common tree victims of Japanese beetles: Crape myrtle, birch, littleleaf linden, crabapple, purple leaf plum, Japanese maple and Norway maple

  • How to control Japanese beetles: Apply one or two pesticide treatments a few weeks apart.

  • When to treat for Japanese beetles: Act during peak growing season, from mid-June through August.

Symptoms: Large, silky spider webs and tree leaf loss, especially on black cherry trees

  • What insect is damaging my tree: The extremely troublesome Eastern tent caterpillar

  • What do Eastern tent caterpillars do: They chew on foliage, leave behind webs and create an unsightly appearance. On black cherry trees, this pest is a serious threat.

  • Most common tree victims of Eastern tent caterpillars: Black cherry, ash, birch, sweetgum, willow, maple and oak

  • How to control Eastern tent caterpillars: Clip and destroy the tents.

  • When to get rid of tent worms: Wait until winter to remove the silky webs. Your arborist can also apply a treatment to control the larvae.

Symptoms: Yellow spots or leaf curling on new tree leaves, premature leaf drop, a clear, sugary substance on or under your trees, black fungus and lots of ants

  • What insect is damaging my tree: The un-welcomed whitefly

  • What it does: Whiteflies suck plant sap from new, tender tree leaves.

  • How to control whiteflies: You can get rid of whiteflies by using horticultural oil treatment or yellow sticky traps.

  • When to apply whitefly treatment: Whiteflies pose no immediate threat and may be controlled by other predatory insects.

Symptoms: Silky “webs” in trees, chewed leaves, mild to severe leaf loss and branch death with no regrowth on evergreens

  • What insect is damaging my tree: Bagworms, the camouflaged critters

  • What do bagworms do: Bagworms consume tree leaves, often unnoticeably, until severe damage occurs.

  • Most common tree victims of bagworms: Juniper, arborvitae, cedar, spruce, honeylocust, linden, willow, maple, oak, birch, elm and poplar

  • How to treat bagworms in trees: Begin by handpicking and destroying all bags. If that’s not practical, your local arborist can apply an insecticide treatment.

  • When to control bagworms: Remove bags as soon as you spot an infestation.

See any of the above tree pest signs? Ask your local arborist to inspect your trees – for free.

  • The Tree Doctor September 14, 2017 >Hi Troy. From what you described, it sounds like your maple has cottony maple scale. The good news is, there are treatment options. You may find this article helpful, davey.com/arborist-advice/articles/cottony-maple-scale/. Hope this helps, Troy.
  • troy cook September 14, 2017 >maple with white sacs or fungus on tree seems to be killing it already killed younger maple
  • The Tree Doctor August 14, 2017 >Hi Joan. Great question! To make the best recommendation for your tree, we would need to see photos of the bugs on the maple leaves, as treatment depends on proper identification of the bug. You can submit your photos to blog@davey.com. Here if you have any other questions, Joan.
  • Joan Gronnert August 14, 2017 >what solution to bugs on the maple leaf tree living on the leaves how to get rid of
  • The Tree Doctor July 26, 2017 >Hi Carol! Sorry to hear about your trees. We would be happy to come to your property for an inspection! I have passed along your request to your local office to set up a free consultation, so they should be reaching out soon. Or if you’d prefer, you can contact them at 866.254.7922 or daveytree.ca/local-offices/burnaby-tree-service/. Here if you have any other questions, Carol.
  • Carol Morris July 26, 2017 >Would like an inspection of our blue spruce, dogwood and apple trees for disease or mites. Blue Spruce is turning brown inside and looks quite sick this year - About 25 yrs old.
  • The Tree Doctor July 25, 2017 >Hi, Jennifer! We would be happy to provide you a quote for an insecticide application. I have passed along your request to your local office to set up a free consultation, so they should be reaching out soon. Or if you’d prefer, you can contact them at 262.395.7589 or davey.com/local-offices/milwaukee-tree-service/. Here if you have any other questions, Jennifer.
  • Jennifer Meiller July 24, 2017 >I have three mature linden trees that seem to have an insect infestation. Can you provide a quote for an insecticide application please? Thank you!
  • The Tree Doctor June 5, 2017 >Hi Jean. Oh no! Sorry to hear the tree in your front yard is struggling and dropping leaves. We are more than happy to help and figure out what's wrong. I've passed along your request to your local arborist, so they should be reaching out soon to set up a free consultation. After inspecting the tree in person, they'll let you know if it needs to be fertilized, pruned or removed - and how much each service would cost. If you'd prefer, you can contact the office directly at 314-732-4851 or davey.com/local-offices/st-louis-tree-service/#main-form. Talk to you soon, Jean.
  • Jean Dantzler June 2, 2017 >I have these horned oak galls (I think) on my large front tree and it's dropping new growth leaves by the dozens, daily. Please review my tree with me and let me know if it requires fertilizing (and how much you'd charge). I had it pruned some last year, but it's a BIG tree. Need to know if proper care can cure it or if I'm looking at removal. thx.
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