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Common Garden Pests & Insects

Common insect pests that damage ornamental plants and flowers

Our camera caught many insects in action over the years...

While working in residential and commercial landscapes over the past few decades, we've often encountered many of the same insect pests damaging the same plants. On this page we share our photos of these pests along with some brief additional comments on the damage caused by these plant pests.



Aphids (plant lice)

Aphids are very common on new growing branch tips
Aphids are very common plant pests and often work in a symbiotic relationship with ants.  They especially like Spirea -- in this case the 'Snow Mound' variety.


Bagworm damage on Arborvitae
These caterpillars create silk bags camouflaged with foliage from the host plant. Bagworms become much more noticeable as bags turn brown.

Arborvitae bagworm caterpillar sticking his head out for a bite
By late summer, this Arborvitae was showing widespread bagworm damage. Controls: apply Bt or an approved insecticide in June, or hand pick the bags in late Fall to destroy overwintering eggs.

Black Vine Weevil

Black Vine Weevil adults do the noticeable "C-shaped" leaf notching on Rhododendron leaves, but the real damage is caused by the root weevil stage which damages the roots. A root drench of insecticide to control the grub stage is usually applied in late June in the Pittsburgh, PA area.


Carpenter Ants

Carpenter Ant damage

Carpenter Ant galleries in a cherry log
We wouldn't ordinarily include Carpenter Ants with other plant insect pests. However, after seeing a "tunneled out" wild cherry tree break off at the base during a windstorm, it only seemed appropriate. Carpenter ants weakened the heartwood of the tree enough that it blew down, hitting a house. Carpenter ants are drawn to wet wood.

Dogwood Borer

Dogwood Borer holes in the trunk of a Dogwood tree
Notice the "drill holes" in this trunk

Dogwood borer is the most significant pest of Flowering Dogwood (Cornus florida). Dogwoods planted in full sun are much more likely to be impacted by dogwood borer than those planted in partial shade, due to their increased stress level. Avoid damaging trunks with weedeaters and lawnmowers. Adults emerge in late May.

Eastern Tent Caterpillar

Eastern Tent Caterpillars in the crotch of a tree
Eastern Tent Caterpillars arrive quickly in the spring and are easily distinguished by their location in the "crotch" of a branch.  In stark contrast, Fall Webworm tents are formed at the branch tips.


Japanese Beetle Grub
While aerating this home lawn in September we noticed the sod was loose and had several brown areas. Further examination revealed 'C-shaped' Japanese Beetle grubs. Grubs eat grass roots causing sod to brown and feel loose when you pull up on it. The many different types of soil grubs are identified by the pattern of hairs on their rear ends which are known as 'rasters.'
Grub damage

Japanese Beetles

Japanese Beetle
The adults suddenly appear around the 4th of July and "skeletonize" the leaves on plants. Purple-leafed plums are one of their favorites. The larval stage is best known for the damage it causes to lawns by eating the roots off grass, causing large brown areas of turf, mostly in the fall and spring (see 'grub' photos above). Chemical lawn treatments are timed for late-summer into early-fall when the grub is most vulnerable. Biological control: Milky Spore is effective against Japanese Beetle grubs.

Lace Bugs

Lace bug damage on a PJM Rhododendron
Speckled leaves on PJM Rhododendrons (photo above), Azaleas and Andromeda (Pieris) are usually a sure sign of lace bugs. Look at the undersides of leaves to detect active adults during the summer months. The adults are 1/8-inch long with clear, lace-patterned wings. The undersides of leaves will also have brown splotches.
Lacebug damage on back of leaf


Pine Needle Scale

Needle scale
This insect will make the needles on your pine look like they have snow on them. It's most commonly seen on Mugho Pines in landscapes, but also infests Scotch Pines. Control the crawler stage in late May with horticultural oil or insecticidal soap sprays. Dormant oil applications in fall or spring are less effective.

"Rodents"... voles?

Tip blight ... NOT.... rodents chewing the bark off stems!
These blue rug junipers (photo above) appeared at first glance to have 'tip blight' fungus.

The branches have been girdled by small rodents
Upon closer examination, small chewing rodents (Voles?) had stripped bark off the branches (photo above) girdling them enough to cause browning foliage on branch tips.  We've seen several cases like this in 2001


Sawflies chew pine needles to stubble
Check your Pines carefully in May for these camouflaged invaders.  Look first for the areas where needles have been chewed to stubble... the caterpillars will be close by.  They can be sprayed or handpicked.

Scale  (Magnolia)

Sooty mold
A black substance on plant leaves usually indicates the presence of a sucking insect excreting excess honeydew. Black sooty mold grows on the honeydew giving the leaves a blackened appearance. This 'sweet' honeydew on the leaves may attract bees as well as ants. Scale insects (white, top left, in photo above) have infested this Magnolia tree.

Scale on Magnolia
Close examination of the tree branches reveals a large infestation of 'bumper to bumper' scale, resembling small oyster shells....these are the Mama scales.  Young scale crawlers emerge from beneath these 'turtle shells.' Dormant oil sprays, properly used, will provide good control of this insect pest, and be less harmful to the environment than most other pesticides. Read and follow label directions, they are there to help.

Scale crawlers
Scale crawlers can be seen emerging in July
on this Magnolia in Pennsylvania

Scale (Lilac)
Lilac Scale

Scale (Juniper
Scale on Juniper
Insect controls for Scale
Dormant season
: Horticultural oil applied in early spring.
Growing season: Contact insecticides that kill young crawlers.


Pesticide usages

Deer browsing

Shedding needles



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