Fall pest invader guide, 2023 edition


August 23, 2023

Photo: genxtek/iStock / Getty Images Plus/Getty Images

Photo: genxtek/iStock / Getty Images Plus/Getty Images

With the shift in seasons comes an unwelcome guest: fall-invading pests. These pesky intruders seek warmth and shelter in our living spaces, causing annoyance and potential health concerns. Drawing from insights shared in earlier publications (El Damir, 2022), this guide offers practical tips for understanding, preventing, and dealing with these seasonal invaders.

Spotting the culprits

As temperatures drop, various pests migrate indoors. Common fall invaders include boxelder bugs (Boisea trivittata), with black bodies and red stripes; cluster flies (Polleniidae), recognizable by their gray color and yellow thorax hairs; and harlequin beetles (Harmonia axyridis, also known as multicolored Asian lady beetles), with distinct “M” or “W” markings at the back of the head. Western conifer seed bugs (Leptoglossus occidentalis), brown with white V-shaped markings, also join the party, along with brown marmorated stink bugs (Halyomorpha halys) with shield-shaped body and brown mottling, clover mites (Bryobia praetiosa), with its unique elongated first pair of legs, reddish or greenish coloration, and sparsely arranged featherlike plates on the abdomen, foreign grain beetles (Ahasverus advena)recognized by the presence of a slight projection or knob on each front corner of the pronotum, and the gravid /mated females of yellowjackets and paper wasps (Vespidae) (yellowjackets tend to have a more robust and stocky body shape, while paper wasps have a more elongated and slender body with longer legs and a more distinct waist between the thorax and abdomen (El Damir, 2022).

Effective prevention

Taking action is key. Seal entry points, replace worn sweeps, and reinforce doors. Applying insecticides with knockdown power to sunny sides of buildings deters pests from getting indoors (El Damir, 2022).

Thoroughness matters

Coverage matters when using pesticides. The careful application eliminates hiding spots. Focus on high entryways like rooflines, favored by cluster flies. Treating potential entry points and under eaves strengthens your defense (El Damir, 2022).

Insecticide application

Follow label instructions and choose insecticides carefully. Opt for long-lasting solutions with knockdown effects to keep pests out (El Damir, 2022). The flexible application covers resting and entry areas of fall-invading pests.

Setting expectations

Communication with customers is vital. After treatment, dead insects may be present and insecticides might take time to work. Live insects could linger due to various factors, but treatment will eventually eliminate them. (El Damir, 2022).

Understanding insecticides

Insecticides work differently – some act fast, while others take time. Applying them at the right time and ensuring proper coverage, especially at entry points, is crucial. Heavy rains and warm sunny days might require a follow-up treatment (El Damir, 2022).


Be proactive against fall-invading pests. Prompt action, careful application of pesticides, and clear communication are your allies (El Damir, 2022). By embracing these insights, homeowners and professionals can enjoy a pest-free fall season.


About the Author

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Dr. Mohammed El Damir, BCE, is technical and training director of Adam’s Pest Control, Medina, Minn.

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