   Lady Beetles are Beneficial - May 16, 2007 Jeff Schalau, Associate Agent, Agriculture & Natural Resources, Arizona Cooperative Extension, Yavapai County Lady beetles, often called Ladybugs, are the most commonly known of all beneficial insects. Both adults and larvae feed on many different soft-bodied insects with aphids being their main food source. Knowing that lady beetles will arrive in your garden helps you tolerate spring aphid populations. Learning to recognize the eggs and stages of the lady beetle life cycle will help you monitor their populations and reduce some gardener’s use of insecticides. Lady beetles belong to the family Coccinellidae. Most people recognize adult lady beetles by their shiny, convex, half-dome shape. They are often orange with black spots. However, given over 500 species found north of the Mexican border, there is much variation in color: from bright colors with spots to dark colors with few or no markings. Most lady beetles are predaceous as both larvae and adults and vary in adult body length between 3 to 7 mm. Aside from aphids, lady beetles can also feed on many other pests such as soft-scale insects, mealybugs, spider mites and eggs of the Colorado Potato Beetle and European Corn Borer. One larva will eat about 400 medium-size aphids during its development to the pupal stage. An adult will eat about 300 medium-size aphids before it lays eggs. About three to ten aphids are eaten for each egg the beetle lays. More than 5,000 aphids may be eaten by a single adult in its lifetime. Usually the life cycle from egg to adult requires about three to four weeks, or up to six weeks during cooler spring months. In the spring, overwintering adult females find food, then lay from fifty to three hundred eggs in or near aphid colonies. Egg masses are small, bright orange ovals laid on end in groups. Eggs hatch in three to five days, and larvae feed on aphids or other insects for two to three weeks. Larvae are multi-colored, often mostly blue with red or orange markings and resemble little alligators (or in Arizona, Gila monsters). Larvae of most species go through four instars (stages between molts) looking similar but increasing in size each time before they pupate. The pupae are often attached to leaves, tree trunks, and structures and look similar to the larvae but are stationary and rounded. The pupae emerge as adults in seven to ten days. There may be five to six generations per year. Convergent lady beetles (Hippodamia convergens) are one of the most common native species. The common name refers to a pair of white convergent dashes on the prothorax (the round plate behind the head). Photos of all life stages of the convergent lady beetle can seen on the web at: www.ipm.ucdavis.edu/PMG/NE/convergent_lady_beetle.html. The multicolored Asian lady beetle has been intentionally imported to the United States for biological pest control. While it is a very effective predator, this hasty introduction has also created some negative impacts. Unlike our native species of lady beetles, the multicolored Asian lady beetle seeks protected overwintering sites in and around buildings. They may occur in any type of structure. Because these exotic lady beetles readily occur on trees, homes in forested areas are often infested. The beetles can form large, hidden aggregations in secluded dark locations inside homes. They periodically invade living spaces, apparently in response to the warm interior temperatures. When disturbed, multicolored Asian lady beetles excrete a yellow-orange body fluid (their blood). The fluid has a foul odor and can permanently stain fabric and walls. People have also reported an allergic reaction to the fluid as well as nuisance biting (they do not break the skin). Needless to say, these impacts have caused concern among those affected and reinforces the need to be careful when introducing non-native organisms to new environments. In Arizona, we have many native lady beetle species. Do not transport them from one place to another. If there is food available or habitat is suitable, they will appear at the proper time. Furthermore, respect and conserve lady beetles (and other beneficial and/or benign insects) by only using insecticides when absolutely necessary to prevent long-term or serious economic impacts. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |