Introduction Lygodium microphyllum is native in Old World tropic and subtropic regions like Australia, Southeast Asia, India, and Africa. First naturalized in 1960’s Invasive FL species now covers 43,000 ha of FL everglades, growing 150% from ‘97-’99. It grows thick, into mats which smother the undergrowth and up over shrubbery and trees, which can carry ground fires into the forest canopy.
Reproduction peaked in wet season but goes all year. 15,000 spores per cm 2 of fertile leaf. The landscape model they have developed shows that, in the absence of aggressive control measures, the landscape coverage of visible L. microphyllum infestations could exceed the current combined coverage of the top five invasive species by 2014, extending north into the Kissimmee River basin and south into Everglades National Park. Volin found that it was probably propagule pressure that did the most to aid in it’s spread across FL along with L. microphyllum’s adaptable reproductive capablility with a mixed mating strategy, high selfing rates, and ability to make intergametophytic crossings help it adapt to environments.
Methods-Exploration Sites were chosen based on similar climates and habitats to where the Florida plants were growing. CLIMEX software was used to compare the climates of West Palm Beach in Southern Florida with L. mircophyllum native areas in Australia and Asia. Most places were visited multiple times to account for seasonal changes in herbivore populations and collections were conducted with hand searches, sweeping, beating of foliage and/or dissection of underground plant parts.
Methods-Arthropod ID Arthropods collected were identified by molecular tools, some specimens were sent on to different systematists 1 to 30 individuals of each sample were taken to ensure consistency throughout the individual locations of research and the 28S rRNA was sequenced for identification as well as taxonomic references and comparisons of adult and juvenile herbivores.
Methods-Host range testing Test plants were kept in 25 degrees Celcius with normal day light. Two pairs of young moths were placed in a moist bag with one fern leaf or small group of pinnae and were left until death or 5 days if eggs were laid. Larve were allowed to develop on these test leaves.
Results-Exploration L. microphyllum was never seen more than a few meters tall and was found growing in many habitats, esspecially wet areas or recent burn sites. Two mites and twenty insects species were collected feeding on Lygodium species, the most seen being the mite Floracaru perrepae and a moth Neomusotima conspurcatlis Table 1??
Results-Herbivores Floracau perrepae was found in all areas researched Female mites laid eggs in leaf curls where they hatch and grow to adulthood. Feeding on the leaf leads to leaf death and eventually pinnae defoliation. A steady state is reached between mite induced death and plant growth until fires when the plant grows rapant without the presence of the mite. The mite seems to only feed on F. microphyllum and F. reticulatum, based on this narrow host range F.perrepae should be a good candidate in fighting the invasive form in Florida, however Australia/Queensland population have not done well there.
Neomusotima conspurcatlis was the predominate insect found on L. microphyllum. Eggs are laid mostly on new growth and larvae first skeltonize and then consume entire leaves as they grow. Although natural populations were only found at low densities they were seen throughout the year and were found after recent fires which is a good sign for dispersal and ability to keep microphyllum in check Pyraustinae sp was found to have larvae that feed similar to the N. conspurcatlis but only nocturnally and were found on no other ferns.
Catclysta camptozonale which was found in areas more similar to the South Florida winter (few freezes a year but subtropical environment). Consumes leaves like the Neomusotima moth. Natural populations were found to be very low except for one documented outbreak in Queensland in 2000 where whole patches of L. microphyllum were consumed Amenia sp a stem-boring moth was found to be a great candidate for Lygodium control as larvae were found to tunnel into the stem causing death of the shoot distal. However, they have not been able to cultivate a species to use in testing.
Different species of Callopistria were collected from Australia and Asia but are also naturally found in Florida where Lygodium grows Sp A was found to consume entire pinnae in a fish bone type pattern making them easy to find. Sp B and C may have too wide of a host range to use against microphyllum.
Neostromboceros albicomus, a sawfly was found to lay eggs in the soil, which may protect against fires, occur in high densities and when emerge defoliate L. microphyllum, making it a good candidate. Acanthuchus trispinifer was not found to be able to breed on microphyllum therefore making it a poor candidate for control although adults were found to do some leaf damage. (picture)
Not good candidates Following were found on Lygodium but wouldn’t make good candidates. Spodoptera litura, Achips maclopis, Pseudococcus longispinus was found to be detrimental to Lygodium but was a generalist and found to kill everything in site. The flea beetle Manobia could not survive on microphyllum. Endelus bakerianus, a leaf mining beetle seems to grow only on microphyllum and adult Lophothestes were found there but it is unknown and untested whether they may be detrimental to other species. Octothrips lygodii was also found to be debilitating to microphyllum but its unknown host range makes it un-usable currently.
Discussion Three other fern species have been considered for biological concern programs: P. aquilinum was found to have 31 herbivorious species but after some study the UK didn’t use any because of ethics in using biological control for native species, even if detrimental to agriculture. However, control for the aquatic fern S. molesta was successful using Cyrtobagous salviniae. Using the Stenopelmus rufinasus weivel to control the fern species A. filiculoides has also so far been successful. This study was conducted and proceeded to have similar results as these previous stories. This study in particular found that for L. microphyllum the herbivores Arcania and Lepidoptera represented the majority.
To get the most diverse collections, they were made over three year sin all season and weather conditions to account for the low population density of many of these insects. Densities were noted to be higher during rain and may be low in general due to the low nutrient level of many of the sampling places, particularly Australia (2/3 nitrogen, potassium, phosorus as FL plants). The mite F. perrepae is the best candidate with its narrow host range to limit effects on other plants and its abundance on L. microphyllum
Summary F. perrepae= mite, best for control b/c of narrow host range Leaf feeding pryalid moths = moths, many good, some have narrow host range, a few host ranges are unknown however. In moths that may be good for control another aspect for concern is their population growth without natural enemies. Stemboring= also considered because of extent of damage done to plant, also good at concealing itself against parasites Sawfly=because pupated in soil which help fire survival and narrow host range
Work Cited Goolsby J, Wright A, Pemberton R. Exploratory surveys in Australia and Asia for natural enemies of Old World climbing fern, Lygodium microphyllum: Lygodiaceae. Biological Control [serial online]. September 2003;28(1):33. Available from: Academic Search Premier, Ipswich, MA. Accessed March 30, 2010. Madeira P, Pemberton R, Center T. A molecular phylogeny of the genus Lygodium (Schizaeaceae) with special reference to the biological control and host range testing of Lygodium microphyllum. Biological Control [serial online]. June 2008;45(3):308-318. Available from: Academic Search Premier, Ipswich, MA. Accessed March 30, 2010 Volin J, Lott M, Muss J, Owen D. Predicting rapid invasion of the Florida Everglades by Old World Climbing Fern (Lygodium microphyllum). Diversity & Distributions [serial online]. September 2004;10(5/6):439-446. Available from: Academic Search Premier, Ipswich, MA. Accessed March 30, 2010