Life can be hard for trees and bushes in St. Louis and throughout Missouri. Bitter cold winter, snow and ice, blazing summer temperatures, long dry periods, windstorms and clay in soil are all ever-present challenges to your trees, bushes and landscaping.

But they’re not the only threats.

A wide variety of pests native to Missouri and the Midwest can keep your trees and bushes under attack, damaging or even destroying them. These pests can act quickly, so it’s important to be aware of their presence and take action when necessary to protect your trees and bushes.

At Hansen’s Tree Service, we specialize in tree care and have extensive experience in spotting and combatting these pests. Below is our the “Ten Most Wanted” list of the 10 pests that threaten trees and bushes in St. Louis and throughout much of Missouri, along with tips for controlling or eradicating them.

1. Emerald Ash Borer (Agrilus planipennis)

Why It’s a Threat
The Emerald Ash Borer is an invasive insect that targets ash trees, which are common in St. Louis and Missouri. The larvae of this beetle bore into the bark of ash trees and disrupt the flow of water and nutrients, ultimately killing the tree. Emerald Ash Borer infestations often go unnoticed until significant damage has been done.

Control
If caught early, this borer can be controlled with systemic insecticides that are absorbed by the tree. It’s important to regularly inspect ash trees for signs of infestation, such as D-shaped exit holes or wilting leaves. In severe cases, removal of the affected tree may be necessary to prevent the spread of the insects to nearby trees.

2. Japanese Beetles (Popillia japonica)

Why It’s a Threat
Japanese beetles are known for their voracious appetites, feeding on the foliage of a wide variety of trees, bushes, and plants. These beetles can defoliate entire trees if left unchecked, weakening them and making them more susceptible to disease and other pests.

Control
The best way to control Japanese beetles is through manual removal and the use of pheromone traps. Insecticides can also be applied to trees during the beetles’ active season, typically from late June to early August.

3. Bagworms (Thyridopteryx ephemeraeformis)

Why It’s a Threat
Bagworms are caterpillars that create distinctive “bags” made of silk and plant material. They can defoliate trees and shrubs, particularly evergreens, causing significant damage over time. Large infestations can weaken trees and shrubs, making them more vulnerable to other pests and diseases.

Control
Bagworms are easiest to control in their early larvae stage. Pruning infected branches or using insecticides can help eliminate these pests before they can cause major damage.

4. Southern Pine Beetle (Dendroctonus frontalis)

Why It’s a Threat
Southern pine beetles are particularly dangerous to pine trees, and they attack weakened or stressed trees. The beetles tunnel beneath the bark, disrupting the flow of nutrients and ultimately killing the tree. In severe infestations, entire pine stands can be wiped out.

Control
Preventative measures such as thinning dense pine forests and removing weakened trees can help limit the spread of the southern pine beetle. Insecticides may also be used on trees at high risk of infestation.

5. Cottonwood Borer (Plectrodera scalator)

Why It’s a Threat
The cottonwood borer is a wood-boring beetle that attacks cottonwood, willow, and poplar trees. The larvae tunnel through the tree’s trunk, weakening the structure and causing dieback. While the adult beetles do not harm trees, the larvae can severely damage them over time.

Control
The best way to control cottonwood borers is to inspect trees regularly for signs of infestation, such as holes in the bark or sawdust-like material. Insecticides can be applied to trees in the early spring before the beetles lay eggs.

6. Tree Aphids (Aphidoidea)

Why It’s a Threat
Tree aphids are small insects that suck sap from trees and bushes, weakening them and causing leaf curl and yellowing. Aphids also secrete a sticky substance called honeydew, which can attract mold and other pests. While aphids generally do not kill trees, prolonged infestations can lead to significant stress.

Control
Controlling aphids can be as simple as spraying trees with a strong stream of water to dislodge them. For more severe infestations, horticultural oils or insecticidal soaps can be applied.

7. Spongy Moth/Gypsy Moth (Lymantria dispar)

Why It’s a Threat
Gypsy moth larvae are notorious for defoliating trees, particularly oaks, maples, and birches. Large outbreaks can lead to significant tree stress, making them more vulnerable to disease and other pests. In some cases, defoliation can even lead to tree death if repeated over several years.

Control
The use of pheromone traps can help monitor and reduce the gypsy moth population. For infestations, insecticides or biological controls such as the bacterium Bacillus thuringiensis can be effective.

8. Oak Wilt (Bretziella fagacearum)

Why It’s a Threat
Oak wilt is a fungal disease that affects oak trees, causing rapid defoliation and often leading to tree death. The fungus spreads through root grafts between trees, making it particularly difficult to control in larger stands of oak.

Control
Preventing oak wilt requires careful pruning practices, especially during the growing season when the fungus is most active. Infected trees should be removed, and fungicides may be applied to prevent further spread.

9. White Pine Weevil (Pissodes strobi)

Why It’s a Threat
The white pine weevil attacks the terminal leaders (top shoots) of white pine trees, causing the tree to become deformed and weakened. While it doesn’t usually kill the tree outright, repeated attacks can lead to significant damage.

Control
Trunk injections with insecticides or early pruning of infested branches can help mitigate the damage. Preventing infestations is easier when trees are healthy and growing vigorously.

10. Scale Insects (Coccoidea)

Why They’re a Threat
Scale insects are small, immobile pests that attach themselves to tree bark and sapwood. They suck out sap, weakening the tree and leading to yellowing or stunted growth. In severe cases, scales can cause the death of the tree.

Control
Control scale insects through the application of horticultural oils or insecticides. Regular monitoring and early detection are key to preventing large infestations.

Are Your Trees Being Threatened by a Pest on Hansen’s Ten Most Wanted List? Contact us Today!

The key to stopping these pests is recognizing their presence and quickly taking steps to eliminate them. Regular inspections, proper tree maintenance, and early intervention can keep your landscape thriving and free from the worst pest damage. If you’re concerned about pests damaging your trees or bushes, our certified arborists and tree care specialists can help you assess the situation and take the steps necessary to protect your trees.r you.

Contact us today! We’re here to help!