Aphid Predator and Parasite
Posted by romeethredge on June 30, 2012
Aphids have been real bad lately, sucking plant juices, slowing plant growth and leaving behind honeydew and sooty mold. Fortunately we have some help from nature in the form of parasites and predators. The lady beetle and its immature stage which is pictured here and looks quite different from the adult. Often folks ask how to control this bad looking pest that turns out to be a good guy.
Commonly referred to as Lady Bugs these helpful critters are not bugs at all, they are beetles and their correct name is The Ladybird Beetle. There are about 400 different types of Lady Bugs in the Coccinellidae family inNorth America and about 4,000 species worldwide. The most common beneficial species inNorth America is the Convergent Lady Beetle.
All Lady Bugs have similar life cycles. Eggs are laid in the spring. When hatched the larvae will feed for several weeks and pupate into adults. The adults feed through the fall, then either lay eggs and die, or hibernate over the winter, waking in the spring to feed and lay eggs.
Lady Bugs are the most widely used and best known form of biological pest control. Famous for their control of aphids, Lady Bugs will also consume large numbers of whitefly, mealybugs, scales, mites and many other soft bodied insects as well as bollworm, broccoli worm, cabbage moth and tomato hornworm. A Lady Bug will consume up to 1,000 aphids in it’s lifetime in both its larval and adult stages.
In the other photo I have a parasite, a wasp that is laying tiny eggs inside aphids that will develop inside the aphids and in a little while you will see the brown blown up carcasses of killed aphids and often a circular hole where the adult wasp has emerged. This is a valuable aphid parasite, Lysiphlebus testaceipes. Dr John Ruberson, UGA Scientist says “When this parasite is abundant, it can cause rapid and dramatic reductions in aphid populations, and their activity is easily detected as healthy aphids are replaced by swollen and hardened aphid `mummies.’ Here’s some more information about the parasite from Cornell University. “The female wasp inserts an egg into the aphid and in about 2 days a tiny wasp grub hatches and feeds internally on the living aphid. The wasp grub completes feedings in about 6-8 days, resulting in the death of the aphid. Movement of the wasp grub inside the aphid expands the aphid, giving it a swollen appearance. The larva cuts a hole in the bottom of the aphid, attaches the aphid to a leaf with silk and a glue, and the dead greenbug changes color from green to a brown “mummy”. Then the wasp grub molts to the pupal stage, and after 4-5 days a wasp emerges by cutting a circular hole in the top of the mummy.
Hopefully soon we will see some more help from nature to control this pest. A naturally occuring disease usually comes in abouth this time of year here to wipe out most of our aphids on cotton.. This fungal epizootic typically occurs in late June or early July depending upon location. Once numerous gray fuzzy aphid cadavers are observed in a field we would expect the aphid population to crash due to the fungus in about a week. Aphids add stress to plants by feeding on and removing plant juices. Heavy accumulations of honeydew, yellowing terminals, and plant stunting should be considered prior to treating aphids.