Hackberry Psyllid
With temperatures in the KC Metro area so variable this fall season, I am sure many people have been opening their windows to let in some cooler temperatures. By doing so, perhaps you have noticed some tiny critters trying to amass on your screen. Our hotline at the extension office has been flooded with Johnson County residents wanting to know what and why small bugs are gathering on their screens. 
One insect we commonly see on window screens late in the fall is hackberry psyllids (Pachypsylla spp.). These insects are responsible for creating hackberry nibble galls on the leaves of hackberry trees (Celtis occidentalis). If you or your neighborhood have many hackberry trees, chances are you have seen these “gnat-like” bugs crawling on the mesh of your window. These itty bitty (2-5 mm long) insects will pile up on a window screen by the hundreds and can easily slip through the openings. Why are they doing this, you might wonder? They are looking for a cozy spot to overwinter. Adults will hibernate once temperatures get below 40° F. Usually, hackberry psyllids will overwinter in the bark of hackberry trees or other surrounding trees. However, a house with climate-controlled air is a close second.
Asian lady beetles (Harmonia axyridis) are another nuisance we see around the outside of the windows when temperatures start to drop. As larvae, these insects benefit your garden because their diet mainly consists of aphids. As adult beetles look for a nice spot to overwinter, areas on a house that receive afternoon sun are very appealing. It only takes one female to land on a window and release a pheromone to attract many more beetles to that spot. The aspect that makes them a nuisance is not just the collection of dead bodies that will appear on your windowsill, but if these insects are crushed, they can emit a foul-smelling yellow liquid that can potentially stain objects they come in contact with. Over time, the crushed or uncrushed dead beetle will dry and turn to dust, which can affect people’s allergies and asthma.
Other pests that can find their way inside your home are lace bugs (Corythucha spp. and Stephanitis spp.). These insects can be found on many landscape plants around your neighborhood. In small numbers, they aren’t that noticeable. When populations are high, they seem to be everywhere, causing damage to more than one type of plant. They also seek out spots to overwinter, and one large factor is artificial light. Lamps, ceiling fans, porch lights, and other light sources inside your home can bring these insects to you. The worst part about these bugs is that they bite. They use their piercing-sucking mouthparts to jab into your skin to see what you taste like. It feels very similar to a mosquito bite. However, it doesn’t leave as much of an itching sensation.
Many different types of insects and arachnids will try to seek refuge inside your home this winter. Some will try to make their entry in through the window, others will find cracks along your door. Some lucky ones will get in when you open the door for a few seconds. Don’t be alarmed at the sight of a few; they are just looking for a winter home. If pest numbers get too out of control inside your home, consult a professional.
by Markis Hill, Horticulture Ornamentals and Turf Agent, 2024