Asian Lady Beetle Identification
The Asian lady beetle was introduced to the United States from Asia to control aphids, scale, and other crop pests from 1978 to 1981. The Asian lady beetle is now widely documented in the areas of the Midwest, Southwest, and Pacific Northwest.
Asian lady beetles are usually recognized as typical ladybugs; however, they are slightly larger than native species. The coloration of this beetle varies from mustard-yellow to a dark reddish-orange. Often, a number of spots are present on the wing covers, but the number varies, and in some specimens, the spots are absent.
The key identifying marks on this beetle are two white, oval markings on the pronotum (just behind its head) and an M-shaped marking may also be present on the pronotum. This beetle (6 to 10mm) is slightly larger than the two-spotted lady beetle (4 to 5mm). Larvae are primarily black with orange lateral stripes.
Asian Lady Beetle Life Stages
The Asian lady beetle goes through four distinct life stages: egg, larva, pupa, and adult. In early spring, female adult beetles lay yellow eggs on the underside of the leaves of host plants near aphids, mites, and scale insects. Eggs hatch in 3-7 days, and larvae begin searching on plants for aphids and other soft-bodied arthropods on which to feed. Larvae molt four times, becoming larger after each molt and enter an immobile pupal stage after the last molt.
After several days, the adult emerges from the pupal case. Development time from egg to adult requires about 15-25 days depending on temperature and food availability. Asian lady beetles produce several generations of offspring per year. Later in the fall, just before the first frost, adult Asian lady beetles seek shelter to spend the winter.
Are Asian Lady Beetles Dangerous? Do They Bite? Threats
Although Asian lady beetles may bite, their bite does not seriously injure humans or spread diseases. If crushed, the beetles will emit a foul odor and leave a stain. The dust produced from an accumulation of dead beetles behind wall voids may trigger allergies or asthma in some people.
Asian lady beetles are voracious predators of crop pests and produce several generations per year. Their tendency to aggregate and their ability to enter structures may cause this insect to become a significant structural pest. There have been reports of hundreds and even thousands of these beetles found in and on homes.
Starting in October, during warm sunny afternoons following a cold night, Asian lady beetles congregate outside houses, sheds, and other buildings in search of overwintering sites. They may be found in attics, wall voids, on siding, and are attracted to light. These beetles normally enter homes on the southern and western exposures (sunny side) of structures. They are attracted to sunlight and are often found in windows where many expire.
Asian Lady Beetle Extermination and Control In San Francisco
Asian lady beetles become a problem for homeowners when they move inside homes and structures. Prevention is the most effective control method. Follow these preventative tips to deter an Asian lady beetle infestation:
- Use a good quality silicone caulk and seal cracks around windows, doors, utility pipes, siding, behind chimneys and underneath the wood fascia and other openings.
- Repair or replace damaged screens on doors and windows.
- Replace weather-stripping around windows and doors.
- Plant Mums – Asian lady beetles do not like mums. Be proactive and plant mums around windows and entrances of the home.
- Lady beetles do not like citrus or citronella scents. Make a citrus spray with orange or lemon essential oil diluted in water. Spray liberally around areas such as windows and doors where ladybugs congregate.
- If Asian lady beetles have already entered your home, use a vacuum cleaner to vacuum them up, and dispose of in a plastic bag.