Have you ever thought about a cactus, with its spines and tough skin, and how much it hurts if you fall on one? What about a moth and the possibility of it hurting, or killing a cactus? Researchers at Arkansas State University in Jonesboro, AR are investigating the destructive effects of an invasive species of South American moth that has infested Southeastern United States coastal regions, and possible methods of mitigating the effects.
This particular moth is a cactus boring moth that lays its eggs on the cactus, and once the eggs hatch, the larvae (caterpillars) burrow into the cactus. The caterpillars, anywhere between 20 to 150 of them, then live inside the pad and eat everything inside, sometimes destroying the entire plant. A major concern is what happens when this invasive species spreads to the southwest US and Mexico.
Anastasia Woodard, a PhD student at ASU, and other students in Dr. Travis Marisco’s laboratory are studying the native species of North American moth called the Blue Cactus Moth, which does not normally kill cactus. Pricklypear cacti are not only an important agricultural crop, but also a very important part of many ecosystems. The Pricklypear cacti have developed a defense system against the Blue Cactus Moth that includes producing thick mucilage that forces the larvae outside the cactus pads and drowns them, and induced apoptosis, or programmed cell death, which destroys the infected cactus pad, therefore preventing the infestation from spreading to the rest of the plant.
However, the Pricklypear cacti don’t normally defend against the invasive South American moth. This is where Woodard and team come in - they have found that plants that are defending against the native, species are able to signal neighboring plants and induce defense mechanisms against the invasive cactus moth (Woodard et al 2012). Then things start to happen. The invasive caterpillars take much longer to develop, making it more likely that they will meet their end due to predators or parasites before they can reproduce (Woodard et al 2012). The team, in collaboration with other groups at ASU, and at Pennsylvania State University, is researching the identification of the chemicals used to trigger the plants defense system, and developing a natural, plant based pesticide to elevate the plant’s natural defenses. The research is currently in field trials.
When asked about the implications of the results of this research, Woodard responded “Plant to plant signaling has been shown to result in faster, more vigorous plant defense responses, and synthetic plant volatiles as well as genetically modified plants over producing plant volatiles have recently been under investigation as environmentally friendly pest management tools. We were the first to find evidence that volatile plant signals can be used to induce defense against an insect herbivore that a plant would not normally defend against. In addition we’re the first to try to use induced hairy roots, a plant based bioproduction system often used by pharmaceutical companies, to produce defense volatiles.”
Why did Woodard, a researcher with a background in disease ecology and zoology, become involved in this type of research? “This field has so many opportunities for projects that can change how we do agriculture and manage insects. I hope that during my career I will be able to help develop more sustainable, environmentally friendly agricultural practices.”
This project is currently funded by The Garden Club of America, Arkansas Plant Powered Production (P3), the Molecular Biosciences Graduate Program at Arkansas State University, the Arkansas State University Foundation STAR Herbarium Research Fund, and the Arkansas Department of Higher Education.
More information about the Travis Marisco’s lab can be found at http://myweb.astate.edu/tmarsico/page%202.html
Woodard A, G Ervin, T Marsico (2012) Host plant defense signaling in response to a coevolved herbivore combats introduced herbivore attack. Ecology and Evolution 2: 1056-1064.