Pests of the home & landscape

October 3, 2000
Lady Beetle Questions and Answers

Q. Is the Lady Beetle that congregates around homes in the fall a native species?
A. The particular lady beetle in question is not a native species. Its normal distribution is Asiatic and is found in southern Siberia, Manchuria, China, Formosa, Korea, Japan, etc. It is now commonly referred to as the "Asian lady beetle" or the "multicolored Asian lady beetle." Other names have been suggested; however, these names can not be used in the article.

Q. If it is not a native species, why was it introduced into the United States?
A. Lady beetles are predatory insects (they feed on other insects), and the native lady beetles tend to feed on other insects in low growing vegetation. Researchers were looking for a beneficial species that would feed more on pest species in trees, such as pecan, walnut, apple, peach, etc. Circumstantial evidence indicates that this insect is, in fact, doing what it was intended to do - reduce aphid and other pest species in trees.

Q. How does the "Asian Lady Beetle" spend the winter?
A. A number of insects in the order Coleoptera will spend the winter in the adult stage, and this lady beetle is no different. It will move into overwintering sites between October 25th and November 5th. It will remain in this site until trees begin to leaf out the following spring.

Q. Where does the "Asian Lady Beetle" spend the winter in the indicated Asian countries?
A. It was studied extensively in Japan before importation and researchers found it by the thousands in rocky outcroppings. On sunny days as south-facing slopes would warm, the insects would crawl or fly about.

Q. Was there any indication that the insect would use homes or other structures as overwintering sites?
A. Based on available information, there was no indication that the insect used structures as overwintering sites in the Japanese study area.

Q. Why does it use buildings in the U.S. as overwintering sites?
A. There may not be an answer to this question; however, the best guess is that the upright structure of the house represents a hilly area or a rocky outcropping.

Q. When was the insect introduced into the Unites States?
A. Releases were made during 1916, 1964, and 1965 in California. Based on collection data following the California releases, none of the releases were successful in establishing this species in the state. Additional releases were made in Nova Scotia, Connecticut, District of Columbia, Delaware, Georgia, Louisiana, Maine, Maryland, Mississippi, Ohio, Pennsylvania and Washington from 1978 to 1982. Connecticut received an additional release in 1985. Eight Mississippi releases were made between July 12th to October 23rd, 1980. Total insects released in Mississippi were 3,781.

Q. When did the problem start?
A. The first calls to the Entomology Department were in the fall of 1991, and an informal survey showed that about three-quarters of the counties had received some complaints concerning this insect during that year.

Q. Why do such large numbers occur around a particular structure?
A. In the fall, lady beetles will emit a pheromone that attracts other lady beetles. This material is called a congregating pheromone. As beetle numbers increase, so does the effectiveness of the released chemical. Finally, thousands of these insects will occupy an area, and they may then fly to an appropriate site to rest for the winter.

Q. Are these insects damaging to the home; do they bite or cause other problems?
A. Generally, the insects are more of a nuisance than a pest, such as a termite; however, the connotation of "nuisance" varies with the person. They do cause problems when flying about the house in such numbers that they interfere with ones daily routine, and they will stain some fabrics. There are reports of biting, but it is not in the sense of "feeding on the body of the person." These bites may be in response to the salts or other chemicals that may be present on the skin of a person.

Q. Why are more seen on certain days than on other days?
A. This is related to temperature. If our winters were constantly cold, we would probably never know the insects were in the walls or in the attic, however, this is not the case. In our area, we may have three or four days of cold weather and then it will warm up into the high 60s or low 70s. On these warm days, the sides of the houses will warm and the insects will crawl or fly about, and, during these periods of activity, some will find their way into the home. With the arrival of another cool/cold front, the temperatures will fall, and lady beetle movement will cease.

Q. How can I control them?
A. Once they are in the walls, it is difficult, if not impossible, to get them out. A vacuum cleaner can be used to collect those insects that move into the living space of the building. Or, an aerosol spray containing pyrethrums can be used to kill beetles that are flying about the house. If the latter approach is used, be sure to protect food preparation surfaces. Keep in mind that vacuuming and the use of an aerosol will only give temporary relief.

Place a light, either incandescent or black, in the attic with a bowl of water under the light. Beetles that are attracted to the light will fall into the water. Check the bowl every two or three days and remove dead beetles. Replenish the water periodically. I would not recommend the use of an insect electrocuter in this area.

Q. Can I do anything before the beetles enter the wall voids?
A. Yes. The following may give some degree of control:

  • If the house is brick, check the caulking around window and doorframes. If it is not providing a good seal, re-caulk these areas.
  • If the area around the facia board and brick is not caulked, it should be done before the beetles enter the walls.
  • Be sure that all screens over louvers and soffits are in a good state of repair.
  • Apply an insecticide to the outside areas around doors, windows and the facia board. Ortho Home Defense Indoor and Outdoor Insect KillerÆ (RTU) can be used in this manner. This method may or may not work, depending upon when the material is applied and when the lady beetles arrive. If the beetles arrive shortly after the application, it may give some repellency. If the beetles arrive two to three weeks after the application, then it may not give any control or repellency. Weather permitting try to apply the material around the 20th of October.

James H. Jarratt
Extension Entomologist
Mississippi State University

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