REVISED Late Spring Cold and Frost Damage (Horticulture/Urban IPM)

Late Spring Cold and Frost Damage

June 3rd, 2021

In Montana, it is not uncommon to have late spring cold snaps after things have started to produce new growth in the early spring. This can damage newly emerged leaves, shoots, and flowers especially when temperatures dip to the mid-high 20s. This damage is usually noticeable a few days to a week after the freezing temperatures as wilting and browning of leaves and needles, in addition to potential defoliation of severely damaged growth.

With the cold snap that occurred in the last couple of weeks of May, along with the snow that accompanied it, Montanans are now seeing some of the resulting damage to their trees, shrubs, and early season annuals.

Although the damage can look significant and alarming, most of the discoloration that we are seeing in the state is largely aesthetic, and new growth has already started to resume. Although some of these plants may have stunted growth in the early part of the growing season, most will recover when appropriately cared for, since late winter cold snaps rarely have lasting impacts on healthy trees and shrubs.

To learn more about environmental damage to trees and shrubs, visit the following links:

Contact your local extension office for information on caring for your trees and shrubs.

By: Abiya (Abi) Saeed    Extension Horticulture Specialist  (

Alert Period: 05/25/2021 - 07/06/2021
Submitted By: Abiya Saeed
Grasshoppers in the Yard and Garden_Statewide (Horticulture/Urban IPM)

Grasshoppers are becoming an issue around the state. Once grasshoppers are adults and have entered the yard and garden, management is extremely challenging.

See this link for more information and for a printable pdf (ADA compliant). 

Grasshoppers in the Yard and Garden (

Alert Period: 06/10/2021 - 11/01/2021
Submitted By: Lauren Kerzicnik
Social Wasps in Montana_time to put western yellowjacket traps out (Horticulture/Urban IPM)

We have several social wasps in Montana. Except for the Western yellowjacket, social wasps are typically not aggressive unless their nest is disturbed. Most are beneficial and feed on a lot of our garden pests. Our most common wasps are bald-faced hornets, aerial yellowjackets, Western yellowjackets, and paper wasps. It is time to put out traps for western yellowjackets to trap queens.

See this fact sheet for more information.


Alert Period: 05/25/2021 - 10/01/2021
Submitted By: Lauren Kerzicnik
Brown marmorated stink bug_confirmed in Kalispell (Horticulture/Urban IPM)

The invasive brown marmorated stink bug, Halyomorpha halys, was found flying within a car in Kalispell (Flathead Co.) on May 4, 2021. The stink bug was confirmed for the first time in Montana on January 26, 2021 (from inside a home in Billings).

We currently don’t know what impact it might have on our crops, specialty crops, and as a nuisance home invader across the state.

See this link for more information on the stink bug

Brown Marmorated Stink Bug - MSU Extension IPM Program | Montana State University

Alert Period: 05/20/2021 - 11/30/2021
Submitted By: Lauren Kerzicnik
Codling Moth_statewide (Horticulture/Urban IPM)

Commonly referred to as “the worm in my apple,” codling moths are the primary insect pest of apple and pear in Montana. The adult codling moth typically emerges during apple bloom across the state, which can help growers and homeowners time chemical controls.

There are several options for managing codling moth in backyard plantings. Chemical controls are applied after petal fall and should never be applied during bloom when risk to harming pollinators is high.

See the link to this printable fact sheet for more information (ADA Compliant):

Alert Period: 05/04/2021 - 07/31/2021
Submitted By: Lauren Kerzicnik
It's Tick Season_Statewide_revised (Horticulture/Urban IPM)

It’s tick season and time to look out for ticks. The Forest Service also released a report about an increase in Colorado tick fever cases (vectored by the Rocky Mountain wood tick) last summer (2020) in the Lolo, Bitterroot, Beaverhead-Deerlodge, and Salmon-Challis National Forests.

See the attached fact sheets for more information on ticks in Montana and the report from the Forest Service.

(revised to include Forest Service report)

Alert Period: 04/07/2021 - 09/30/2021
Submitted By: Lauren Kerzicnik
Alert Documents: