CHINQUAPIN The Newsletter of the Southern appalachian Botanical Society Volume 20 (4) Winter 2012 Which Weed is Witchweed? By Lytton John Musselman, Old Dominion University But haustoria do more than this—they also transport growth regulators from the parasite to the host. As a result there is an My introduction to the pernicious African parasitic weed, increase in the ratio of host roots to stems. In witchweed-infested witchweed (Striga asiatica), was accidental and highly illegal. I corn in the sandy soils near Whiteville, it was possible to recognize was a doctoral student at the University of North Carolina doing a a parasitized corn plant just by pulling on its stem—those infected comparative study on haustoria, the organs that define parasitism were more difficult to pull because of the increased number of host in parasitic angiosperms. So when I read a journal article about roots. witchweed in North Carolina, I went to the Whiteville, North The life cycle is complex. Germination of the “dust” seeds de- Carolina area, located, and collected several plants with hosts pends on the right combination of temperature, water, and distance and soil. And I wrote to the USDA laboratory in Whiteville for from the host. Not only can this tiny organism measure these “further information.” Within hours of receipt of my letter I was a factors, it can also determine if the host is suitable. If suitable, the marked man. root hairs clasp By this innocent act, I violated a federal plant quarantine and the host root was soon visited by the head of the lab and a federal quarantine and the tip of officer. With this inauspicious start began my productive and the parasite amicable relationship with the Witchweed Laboratory, with years of seedling root collaborative work on the biology of witchweed. is transformed Witchweed is a small plant, seldom more than 2 feet tall with into a haus- narrow opposite leaves and brilliant scarlet red (rarely yellow) flow- torium that ers—in other penetrates the words, a very host and con- attractive plant nects with the that stands out Witchweed seed in my palm. The longest dimension of a xylem. in monotonous seed is shorter than width of a human hair. rows of corn. It is at this stage that the witchweed “bewitches” its host because it is damaging the host without appearing above ground. When it Like its does emerge to flower, the host could be debilitated. relatives in the After emergence, the parasite produces some of its own food Orobanchaceae through photosynthesis, but would die without attachment to its (many were host. Shortly after emergence the flowers appear. In the popula- once placed in tions I have examined both in the Carolinas and in Africa, all of the the Scrophu- flowers are autogamous, that is, they pollinate themselves. lariaceae), Thousands of seeds are produced by each plant. This prodigious witchweed harvest is exacerbated by the fact that the seeds can remain viable attaches to the in the soil for as long as twenty years. Not surprisingly, control is a roots of its hosts huge problem especially in less developed countries. An intensive through special- quarantine and eradication program by the U S Department of ized structures Agriculture brought the parasite under control and witchweed is no Witchweed in Botswana where it can be a major con- straint on grain production. called haustoria. longer a problem here. Haustoria form How did this African plant arrive in the Southeast? No one is the physiological and morphological bridge between parasite and certain. One intriguing possibility is that seeds were carried on host and are the salient feature of parasitic angiosperms. Though wool from Africa. Al Radford told me that one of the places to witchweed haustoria are small (seldom more than an inch wide) find previously unreported plants in the Carolinas was around a they exert a powerful pull on the host, diverting materials carried in wool carding mill near the coast of South Carolina and suggested the water stream to the parasite. that was the origin of the infestation in the 1950’s. Once it was Witchweed continued on Page 29 26 Chinquapin 20 (4) The Newsletter of the Southern Appalachaian Botanical Society SABS Officers and Newsletter Editor From The Editor’s Desk: undertook this task with the publication of the Castanea journal. It was just that the Wendy Zomlefer J. Dan Pittillo, Newsletter Interim Editor less technical information had a good outlet President (2012-2014) Members will appreciate my interest in for members, hence we started the newslet- Department of Plant Biology 2502 Plant Sciences getting the newsletter available to member- ter as a way to broaden these topics. Profes- Athens, Georgia 30602 ship, having finished the second year as in- sors, please encourage your students to take Phone: (706) 583-0389 terim editor. The Chinquapin, though not advantage of this opportunity. [email protected] an peer-reviewed publication but certainly And now we have the willing colleague, reviewed at least by an editor, has the ad- Dr. Joe Pollard, busy as he must be as a full- Lytton Musselman vantage of getting information out in print time professor at Furman University, to take Past President (2012-2014) more quickly. I believe it is an excellent on this added task without compensation. Department of Biological Sciences way for students to get into the publishing So, it would be great if you members would Old Dominion University mode and easier way for members to share welcome him and at least drop an email Norfolk, VA 23529 (757) 643-3610 their thoughts to all members. Certainly note of thanks for his generous willingness [email protected] this was in the mind of Earl Core and those to carry on the torch of good will and good at University of West Virginia when they botanical knowledge to be shared by all. Charles N. Horn Treasurer (2010-2014) Biology Department Witches’ Broom 2100 College Street Newberry College By Bob Gilbert Newberry, SC 29108 Have you ever looked up into a tree canopy and spotted what appears to be squirrel’s (803) 321-5257, fax (803) 321-5636 nest, but on closer inspection you find it alive with atypical needles or leaves and abnor- [email protected] mal growth patterns? These masses are called witches’ brooms. There are various causative Michael E. Held (2012-2016) agents. The most commonly seen brooms are on hackberry (Celtis). In fact multi-brooms Department of Biology on a deciduous tree is a good clue it may be a hackberry. A mite and a mildew fungus cause Saint Peter’s University these brooms1. Other brooms are caused by different sources. Cherry and blueberry brooms Jersey City, NJ 07306 are caused by a fungus and 201-761-6432 pine brooms by a rust, while [email protected] viruses on peaches and black locust can create abnormal Ruth Douglas growth2. The name evolved Recording Secretary (2009-2013) in ancient times when 101 Wildflower Drive Charlottesville, VA 22911 brooms were often found (434) 293-6538 in old trees in very old [email protected] cemeteries. It was believed they occurred where a John Pascarella, Editor-in-Chief of witch had rested during her Castanea (2009-2013)* nightly travels3. Now that Dean, College of Sciences, Box 2209 witches are almost extinct it Sam Houston State University is understood that stresses Huntsville, TX 77341 Witches’ brooms in Prunus sp. from both environmental Phone: (936) 294-1401 [email protected] factors and parasites can induce these curious growths. Also a broom that originates from one central bud on a pine can result from a genetic change3. Jean Baldwin Another feature about brooms is that pieces can be rooted or grafted and rarely revert Managing Editor of Castanea back to normal growth patterns. Most stay small, becoming dwarf or miniature plants. They 810 East 10th Street can produce seeds that m ay have further variations. When you find miniature plants, espe- Lawrence, KS 66044 cially conifers, in a nursery almost always they were started from a broom. In fact a whole [email protected] new industry has evolved of miniature, semi-dwarf or dwarf conifers that appeal to people with rock gardens and bonsai collections. J. Dan Pittillo, How do you collect a broom, as they are often high up in an old tree? The tree could be Newsletter Interim Editor 675 Cane Creek Road climbed and the broom cut down or a crane would enable the same collecting technique. Sylva, NC 28779 But most often a shotgun is used. A shower of broken pieces rains to the ground. The entire (828) 293-9661 broom mass would not survive left whole as there are no roots. So roots have to be created. [email protected] Trees like pines do not produce roots easily. So the small portions (scions) are grated on rostocks of the same type. Most commonly pine brooms are grafted on Western White Pine rootstock because it is very vigorous in our climate. In fact there are seedlings grown by specialized nurseries for rootstock grafting. Witch’s Broom continued on Page 30 The Newsletter of the Southern Appalachaian Botanical Society Chinquapin 20 (4) 27 A Field Trip with Mark Catesby By Amy Hackney Blackwell Let’s organize a field survey, starting 290 years ago! I know that’s any or all images to anyone who sends us a disk drive (500 giga- strange grammar, but bear with me. Think of the potential – we bytes could hold them all). could get an idea of what was growing before widespread European Last winter Patrick and I worked our way through the images settlement, before the construction of roads and cotton farming from the two Catesby volumes, H.S.