Western Boxelder Bug

General Description

The western boxelder bug is another piercing and sucking insect like stink bugs and lygus bugs that can cause fruit damage later in the season and render fruit unmarketable when present in high numbers.


Boxelder (Manitoba maple) and other seed-bearing maples are preferred for egg-laying; adults will feed on foliage of other non-seed bearing maples as well as ash trees. They will attack the fruit of apples, pears, cherries, peaches and plums later in the summer.


Boxelder will cluster on fruit in the late summer when searching for food and overwintering sites. However their damage is spotty (orchard margins) and generally not significant. They pierce the fruit to extract nutrients, leaving the tissue discoloured and corky at the feeding sites and somewhat pitted, rendering the fruit unmarketable (Fig. 1). The damage looks very similar to late season stink bug damage.

Figure 1. Apples damaged by western boxelder bug feeding. (Gayle Krahn)


They are a nuisance around dwellings when they congregate on south-facing walls in the fall and spring.


Nymph - young nymphs are bright red and becomes marked with black lines as they mature to gradually resemble adults and develop wings.

Adult - flat, elongate, gray to black 10-14 mm long body with distinct red lines crisscrossing the back (Fig. 2). 

Figure 2. Western boxelder bugs. (Gayle Krahn)


Life History

Overwinter as adults in sheltered locations in and around orchards, including tree bark crevices, buildings, pole stacks, wood piles and bin piles. Adults emerge in the spring to feed on host trees before mating. Females lay eggs in bark crevices of host trees where the subsequent nymphs feed on the developing seeds and foliage.  


Visual inspection of fruit tree hosts nearest non-tree fruit hosts is the most practical way to detect boxelder bug presence. They are usually found congregated on fruit. 


Cultural Control

Removing host trees, especially female boxelder (Manitoba maple) near the orchard may help reduce boxelder numbers migrating into orchards.

Chemical Control

Pesticides applied against stink bugs and lygus bugs will also control any boxelder bugs present. Boxelder are a very infrequent problem in orchards.