University of Maryland Extension

September Indoor and Outdoor Insects


Boxelder bug. Photo: William M Ciesla Forest Health Mgmt International, Bugwood.org

(More tips from HGIC)

  • Different nuisance pests, including centipedes, crickets, and spiders are more noticeable inside the home with cooler fall temperatures. Sweep them up, but it is not necessary to treat with pesticides.
  • Over the summer, Indian meal moth may have been breeding in pantry products such as flour, cake mixes, cereals, bird seeds, dried pet food, etc. Remove the source of the infestation and clean all jars and containers that are affected. Do not use insecticides to control these pests.
  • Its early fall - prepare for the invasion of insects! Crickets, ladybird beetles, boxelder bugs, stink bugs, cluster flies, elm leaf beetles, and other innocuous insects will attempt to enter your home this fall for protection. Caulk, weatherstrip and seal up all cracks and entry points around your house foundation, vent openings, windows, and doorways to prevent these critters from coming indoors.
  • September is also the time when various species of flies try to come indoors. Keep screen doors tightly closed, when flies get indoors the best defense is not a spray but the fly swatter. Flies are always attracted to sunny windows, hang fly paper strips in windows to trap them.
  • Ticks will continue to be active throughout the fall and winter. Deer tick populations are especially high around the Chesapeake Bay. Be sure to check yourself and loved ones after working in the yard or hiking in natural areas.
  • Outdoor yellowjacket nests can be treated with a wasp and hornet spray at night. Nests in high or unobtrusive locations should be left alone. Nests in wall voids should be evaluated and treated by a professional pest control company. Yellow jackets are killed by a hard freeze and will not return to last year’s nest.
  • Boxelder bugs are congregating on box elder trees and may be seen in large numbers on house siding, sheds, shrubs or ground covers. The nymphs are bright red. The box elder tree is a weedy, native species. It has compound leaves with three leaflets and resembles poison ivy. The female tree has large clusters of winged seed pods. The box elder bugs congregate on the female trees from the base to the canopy.
  • Avoid storing pesticides over the winter in sheds and garages. Cold temperatures can cause these materials to become ineffective. If you have questions about the efficacy of your pesticides call the manufacturer, using the phone number listed on the label.
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