Question of the Week – Copidosoma
Posted by romeethredge on October 13, 2012
Last week I had a photo of what looked like a caterpillar that had pupated under a soybean leaf. That is a common occurence with soybean loopers and a part of their life cycle. There is something very different about this pupa though. It was invaded by a parasitic wasp, Copidosoma. Officially called Copidosoma floridanum. It’s like something out of a science fiction movie.
And according to UGA Entomologist Phillip Roberts, the Copidosoma parasitized looper does consume more foliage than a non-parasitized looper. So it does not help with the generation of larvae currently feeding, but hopefully help in overall looper control.
University Of Tennessee (It’s ok to quote them since the Bulldogs beat Tennessee this year) Entomologists say Copidosoma is referred to as an egg-larval parasite because its eggs are deposited in newly laid looper eggs. Looper moths deposit eggs individually on leaves. Female Copidosoma wasps search for these eggs and deposit either one or two eggs inside each looper egg that they find. Some time after the looper begins feeding on crop leaves, the Copidosoma egg begins to divide into additional eggs, 2, 4, 8, 16, 32, etc. Eventually a parasitized looper contains around 1000 of these Copidosoma eggs, all of which may have developed from a single original egg and all of which are genetically identical. Thus, if only one Copidosoma egg was initially placed in the looper egg, all of the Copidosoma eggs will be either male or female. When two Copidosoma eggs are initially placed in the same looper egg, they are usually of opposite sexes.
Once the parasitized looper larvae is about 2/3rds grown, changes in the growth hormones of the looper trigger the Copidosoma eggs to hatch and begin feeding within the body of the host caterpillar. Strangely, this also stimulates the host larva to delay its pupation and have additional larval instars, resulting in a larger larva that provides more food resources for the parasites developing within its body. The looper larva remains alive until after it forms its pupal cocoon on the underside of a leaf, but then dies, due to the feeding of the Copidosoma larvae, before it has a chance to pupate. By this time the body of the looper caterpillar is completely filled with the bodies of the Copidosoma parasites, which by this time have also pupated. The resulting looper mummies are initially tan to gray in color and have a grainy appearance due to the presence of the large number of Copidosoma pupae that can be seen through the “skin” of the looper. If one collects one of these mummified loopers and places it in an enclosed container, it will “hatch” within a few days into hundreds of very small, gnat-like adult Copidosoma. In one Louisiana study the average number of Copidosoma to develop from parasitized soybean loopers was 992, but as many as 2500 to 3000 parasites have been recorded from individual larva
This week’s question is about a tree. What kind of tree is this that Kevin Lewis is showing me beside his peanut field?