Love ’em or hate ’em, Ladybugs here to stay


Dr. Bob Gilbert – Columnist

I love the fall season partially because there is less work to do outside. The annuals tended to all spring and summer are now either composited or cuttings have made to root for next year. Trees and shrubs that we have taken for granted yell at us with fabulous fall colors. However, the invasion of Multicolored Asian Ladybugs in November is a big headache and at my house it seems like an invasion. We sweep and vacuum up hundreds daily and some years it is worse. I learned early on that our native Ladybugs ­– sometimes called Ladybirds or Lady Beetles – are beneficial insects as they feed on garden pests such as aphids. The Multicolored or Harlequin Asian Ladybug, a different species, was deliberately introduced into the U.S. Now it has invaded large areas of the U.S., parts of Canada and parts of Europe. In fact, its spread has been recorded as one of the fastest invasions of any introduced insect surpassing even the Japanese Beetle. One hundred thirty Ladybug species have been found in the U.S. There is a great variation in colors ranging from total black, red, orange and yellow. Not all have spots. Asian Ladybugs are distinguishable by the small dark “w” or “M” marking on the white area behind its head. What may account for its vast numbers is that it produces as many as three generations a year. It only takes three weeks for the egg, larvae and adult cycle to be completed. Whereas the native species only has one generation per year. The larvae form resembles a small carrot-shaped alligator without wings. Eggs are laid under leaves and when hatched, the larvae stay on the host until the winged adult emerges. The Asian beetle was first introduced in the U.S .in 1990s with some evidence that it would control aphids and scale on agricultural crops such as pecans and apples. They perform that function well or maybe too well? This insect does not have a natural predator in the U.S. that could control its numbers. Also, it competes with the native species that has had a 14 percent recent reduction in its population perhaps from competition? What is also remarkable is that the Asian lady beetle houses a lethal fungus organism. If our native ladybug or any other insect would happen to eat the eggs or the larvae of the Asian it will die. So, it is deadly to any other insect that might be a potential predator. Like other insects the adults over winter in tight crevices. On a warm sunny day In November they leave their host plants and swarm in vast numbers presumedly looking for a place to over winter. It seems like they prefer houses with tight spots such as door cracks, window screen gaps and broken seals. Our native ladybug maybe is doing the same but they are in such low numbers we do not notice them. Asian Ladybugs have an unpleasant odor and produce a yellow-orange stain when crushed. Good reasons to keep them out of the house. They are aggressive and can even bite. As I was writing, this one landed on my neck and bit me. Asthma sufferers are bothered by these insects. Multi-spotted individuals tend to be females but then the number of spots vary greatly from one individual to another of the same species. In Brussels there is a legend that when a ladybug lands on your arm the number of spots will tell you how many children you will have. Hopefully only one lands at a time. So, what can we do about this nuisance? First of all, during the growing season they are doing their job controlling aphids. They basically are out of sight most of the year. Secondly, you cannot eliminate all of them even if that was a good idea. There are non-selective insecticides that can be used as a spray outside and bug-bombs for indoor use. Remember that when using a non-selective spray, you are killing good insects as well. Sealing cracks and openings in our houses helps especially around doorways so the bugs will not attach themselves to your clothing as you enter your house. There are ladybug funnel traps available that could help reduce your local population. We already have at home the most effective control – a vacuum cleaner. We do need to be thankful that they can not survive our cold winters unless protected. Hopefully the agency that introduced this insect has learned something. It is important to know what predator controls an insect population in its native habitat. For a potential new insect introduction do we already have a similar predator? Most likely not. Insects will only feed on a genetically predetermined host. They do not graze or sample. In theory when introducing a new insect, the predator that controls its population should also be introduced. But then will it become a pest? It is fair to say the some of the beetles were most certainly introduced by accident. Rigid plant inspections and even quarantine of imported plants helps reduce that kind of risk. I have a friend who has a bonsai nursery. He imports large numbers of bonsai plants from Japan. They cannot be bare rooted for any length of time and survive. The imported bonsais are quarantined in their original Japanese soil in separate isolated greenhouses for one year. Close inspection makes sure no new pests or diseases are present either in the soil or on the plants. The USDA monitors this quarantine process carefully. Now there is almost an identical problem with another Asian insect – the Brown Marmorated Stink Bug. This was an accidental introduction first found in the U.S. in 1998. Marmorated means marbled or mottled. This serious pest is a sucking insect that feeds on agricultural crops. It is accurately named, it stinks. In late fall it invades houses sometimes in large numbers while attempting to overwinter. It has no natural predators in the U.S. In Japan there is a small parasitic wasp that lays its eggs only on the Brown Marmorated Stink Bug. There are no plans to introduce the wasp because I assume it, too, could become invasive? It seems like we are experiencing a fair number of invasive Asian pests and invasive Asian plants. I have often wondered if Asian countries are having the same problem from our exports? They do not have our controlling predators nor do we have theirs. Dr. Bob Gilbert, now living in Franklin is cofounder of Smith Gilbert Gardens in Kennesaw Ga. Karen Lawrence is a prefessional photographer of botanical subjects and wildlife is from Franklin, N.C.