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Overwintering Pests and How to Manage Them

What Are Overwintering Pests?

Humans have adapted to living in extreme cold – the residents at Longyearbyen can attest!

But how do pests cope? How do they survive the winter?


A California Winter’s Tale

“Ugh, it’s freezing!”

In an undefined coastal city, the cries of the Californians go unheeded by the rest of the U.S.

Eye roll It’s not the North Pole, after all.

But it can feel like it when temperatures reach below 45F at night!

We may not have traditional winters, but our insects do hide away to reemerge in the spring, ready to conquer our plants and homes.


What are Overwintering Pests?


The most common overwintering pests in Southern California are mealy bugs, leaf miners, and whiteflies (oh my)! Overwintering pests survive winters by finding relatively stable, warmer shelters and staying there. According to the Smithsonian Institute, overwintering pests can hide inside wood (the trees nod knowingly), in leaf litter, under the soil, and even in your home!


What To Do?

You’ve called a Sims Tree Health Specialist, and they’ve created a treatment plan to help reclaim your plants and property from overwintering pests.

Our ISA Certified Arborist recommends a systemic soil drench for your evergreen tree.  The treatment circulates into the tree, goes up into the leaves, and puts up a good fight against those overwintering pests!

For deciduous trees, our ISA Certified Arborist recommends a topical oil spray.

It’s essential to have service done before it gets too cold and during dormancy. That is, after the leaves have fallen but before buds begin to break.

Winter forest and trees


But California Doesn’t Have Winters!

Unless you’re in Big Bear, you’re kind of right – and that’s the problem.

Winters here can be above 70F for up to a week at a time, creating ideal temperatures for overwintering pests to leave dormancy!


Further Prevention

The best way to prevent overwintering pests from overcoming a tree is to keep up with treatment plans recommended by our ISA Certified Arborists.

Additionally, checking your trees for these signs can help:

Leaf miners tend to overwinter in between the layers of a leaf.

If a tree has rough bark, tear back a small piece to inspect for tortoise beetles seeking warmth between the layers.

Inside the heavy foliage of a citrus tree (Southern California is filled with those), look for signs of aphids and psyllids.


Home for the Holidays

Overwintering pests shouldn’t call your trees home for the holidays!

Check trees and yards for signs of overwintering pests and call your ISA Certified Arborist at Sims Tree Health Specialists, Inc. to prevent further infestations in the spring.


About Sims Tree Health Specialists, Inc. 


Sims Tree Health Specialists, Inc. is dedicated to the preservation, education, improved health, and safety of trees. Sims THS has provided California’s Urban Forests with premium healthcare since 1972. To learn more, visit our website:

Sims THS offers services with our ISA Certified Arborists in the following:


Diagnosis and Disease Management, Pest Suppression, Organic Solutions, Fruit Suppression, Drought Protection, and Arborist Assessment Reports and Preservation Plans.

In addition to providing quality tree health services, the Sims family is known for their educational pursuits. In 1996, they started the Sims Tree Learning Center (TLC), a 6-acre botanical garden and research facility sponsored by Sims Tree Health Specialists, Inc. The facility houses multiple types of gardens including a cactus and succulent garden and one of the largest collections of Palms in the Inland Empire. Learn with us!


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