As we continue our sojourn through warm and sunny South Florida, we arrive at Sanibel Island and meet two more non-native organisms that now call Florida home. Two weeks past we met the beautiful Green Orchid Bee in Selby Gardens and last week we met the noxious killer of cycads, the Cycad Scale, in Sarasota. This episode begins with a rather handsome vine introduced to Florida in 1905 called air potato. Its curious name arises by virtue of the aerial tubers produced by the vine that very much resemble russet potatoes. The technical name for these reproductive structures are bulbils and spread of this vegetation-choking plant is largely through human transport of bulbils. Air potato is now considered one of the most invasive alien plants in Florida. Conventional methods of management include use of herbicides, destruction of bulbils, and rogueing vines out of vegetation and soil. However, between 2009 and 2011, collections of a highly specialized leaf beetle, Lilioceris cheni, the Air Potato Leaf Beetle were made in Nepal and China. In 2011, after careful evaluation, the first releases of the beetle were made and by 2015 more than 400,000 beetles had been reared and released around the state.
Watch as an adult Air Potato Leaf Beetle feeds while a larva takes a stroll on a leaf of the invasive air potato.
My first encounter with the leaf beetle took place on Sanibel Island on the edge of a parking lot where leaves of the air potato vine were in tatters, having suffered the jaws of many larval and adult leaf beetles. Gorgeous red and black adult beetles consume noxious foliage of the vine and convert leaf tissue into eggs that are deposited on the surface of a leaf. This flamboyant coloration likely warns visually-hunting predators that this meal may be distasteful. Leaves and other parts of the air potato are laden with toxins and, although beetles thrive on them, air potatoes are not recommended for human consumption.
Female beetles lay upward of 1,900 eggs during their 5-month lifespan. Eggs hatch into voracious larvae that chew ragged holes in leaves. In addition to their orange and black coloration, larvae have another rather nasty trick to ward off potentially lethal attacks by predators. As they consume and process leaves, they pile excrement upon their back. Image the surprise of a hungry predator ready to enjoy a juicy beetle larva that winds up with a mouthful of crap. How clever! The good news in this story is that the beetle is now widely spread throughout the state and a survey of several release locations revealed reductions in both the number of bulbils produced by vines and an accompanying reduction in the density of vines. Way to go tiny heroic beetles!
Bug of the Week thanks Dr. Paula Shrewsbury for images used in this episode. The informative article “Classical Biological Control of Air Potato in Florida” by T. D. Center, W. A. Overholt, E. Rohrig and M. Rayamajhi was used as a reference for this episode. You can check it out at this link: https://edis.ifas.ufl.edu/in957#FIGURE%203