Prospects for biological control of Old World climbing fern -Encouraging results with the brown lygodium moth and

update on other agents

Anthony Boughton & Ted Center

United States Dept. of Agriculture - Agricultural Research ServiceInvasive Plant Research Laboratory

Ft. Lauderdale, Florida

Overview• Background on the weed and where it’s from

• Overview of lygodium biocontrol agents

• Review promising results with the brown lygodium moth- biology, weed impact studies, damage photos

• Status of research on other agents- lygodium moth, Austromusotima camptozonale- lygodium sawfly, Neostromboceros albicomus- lygodium stem borers

Old World climbing fern, Lygodium microphyllum,in south Florida

- One of the most serious invasive, exotic weeds impacting Florida- First reported naturalized in 1968, near Jupiter, Martin County- Spread rapidly and invaded moist habitats across much of southern Florida- Classified as a noxious weed by the State of Florida- Category 1 invasive exotic by FLEPPC

EDD Maps Invasive Species mapping website (http://www.eddmaps.org)

Current distribution

Growth form of lygodiumClimbs….

…and spreads to form mats

Resembles a flowering plant but is a fern

Fern life cycle showingalternation of generations

Meiosis producesspores (haploid n)

Airbornedispersal

Spore germinates intoyoung gametophyte orprothallus

Zygote (diploid 2n)

Dominant sporophytegeneration(diploid 2n)

Gametophytegeneration(haploid n)

Antheridia containingsperm

Archegoniacontaining a single egg

spermYoungsporeling

Mature fern

Fern life cycleshowing alternation

of generations

Sorus

Fern life cycle showingalternation of generations

Lygodium microphyllum:Sperm/eggs on same gametophyte are compatible, so 1 spore -> 1 mature plant

Meiosis producesspores (haploid n)

Airbornedispersal

Spore germinates intoyoung gametophyte orprothallus

Zygote (diploid 2n)

Dominant sporophytegeneration(diploid 2n)

Gametophytegeneration(haploid n)

Antheridia containingsperm

Archegoniacontaining a single egg

spermYoungsporeling

Mature fern

Fern life cycleshowing alternation

of generations

Sorus

Spore production in lygodiumVegetative and reproductive leaflets Underside of a reproductive leaflet

Each sorus -> average of 215 sporesEach leaflet -> average of 133 sori-> 28,500 spores per reproductive leaflet

(Volin et al 2004)Assuming several hundred reproductive leaflets per plant --> millions spores/plant

= HUGE PROBLEM!

Sori

1) Smothers and excludes native plants

2) Changes local fire ecology, because vines carry fire into tree canopies, causing death of trees

--> these impacts fundamentally changing native plant communities & ecosystems

Difficult to manage:

- Burning and mechanical removal not effective for long-term management --> weed rapidly regrows from underground rhizomes

- Herbicides effective, but need for follow-up treatments makes things expensive--> not viable for long-term management over huge areas currently infested

- Production of large numbers of airborne spores allows L. microphyllum to spread rapidly and colonize remote new locations

--> Biological control to provide sustainable long-term management

Two main impacts caused by L. microphyllum

Native range of Old World climbing fern

- Biological control for management of L. microphyllum = Classical biological control

- Search home range of weed for suitable natural enemies (insect & mite herbivores that eat lygodium)

- After testing and regulatory approval, natural enemies that are suitably specific

--> introduced into lygodium-infested areas in Florida--> establish and increase in numbers

--> resulting feeding damage --> depressant effect on lygodium populations

Biocontrol agents for L. microphyllum

Lygodium moth,Austromusotima camptozonale

Lygodium gall mite,Floracarus perrepae

Brown lygodium moth,Neomusotima conspurcatalis

Lygodium sawfly,Neostromboceros albicomus Lygodium stem borers

Brown lygodium moth, Neomusotima conspurcatalis(Lepidoptera: Crambidae)

First released in FL in 2008, & since then has been showing encouraging results

- Native to SE Asia and Australia

- Insect underwent extensive testing in Australia and in quarantine in US to insure thatit wouldn’t pose a risk to native or beneficial plants

- Based on this testing, concluded that the brown lygodium moth had suitable hostspecificity for lygodium biocontrol

- Petition submitted to TAG in 2005. TAG subsequently recommended release

- USDA-APHIS release permit issued fall 2007

Boughton et al 2009. Laboratory host range testing of N. conspurcatalis…..Biocontrol Science & Technology. Vol 19, No. 4, p369-390

Brown lygodium moth, Neomusotima conspurcatalis(Lepidoptera: Crambidae)

Life cycle ofbrown lygodium

moth

Eggs

Caterpillars

Pupa

Adult

Female moths lay an averageof 136 eggs

- Feeding/damaging stage- Molt 5 times

Leaf feeding damage on L. microphyllum

Brown lygodium moth first released 31 January 2008 in Jonathan Dickinson State Park

1000 adults released

Field releases of brown lygodium moth caterpillars

Photos: Patrick Lynch, SFWMD

Field observations at 4-6 months

Field observations beyond 6 months

Photo seriesSurvey plot 23 Oct 2008

Survey plot 13 Nov2008

Fixed point photos

10 Aug 2008 10 Sept 2008

Fixed point photos

13 Mar 2009 February 2010

Vegetation studies to measure impact of brown lygodium moth caterpillars on L. microphyllum

01

2 3 4 5 67

8 9 10 11 1213

14 15 16 17 1819

20

- 20 m, fixed transects installed at release and control sites at time releases were begun

- PVC poles used to consistently mark transect end points

- Vegetation measures assessed:- Linear cover of lygodium in each meter along the 20 m transect

- % lygodium cover in seven 0.5 m x 0.5 m (20 x 20 inch) quadratslocated at 1,4,7,10,13 & 19 m from transect origin

- Transects first measured at or shortly after insect releases were started

- Transects re-measured at intervals thereafter

Results of vegetation studies

Linear Cover Data Quadrat Cover Data

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0 10 20Q

uadr

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um)

Time from transect installation (months)

ControlRelease

In areas where the moth established:-> lygodium cover was reduced by about 50% during first 6-8 months-> at release sites, weed remained at reduced level for next 10-12 months

* asterisk indicates last time-point when control sites were free of the agent

*

0

10

20

30

40

50

60

70

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0 10 20

Line

ar c

over

(% ly

godi

um)

Time from transect installation (months)

ControlRelease

Recent Releases

2008 releases- 7 releases (1000-15,300 insects each) in cypress, of which 6 established -> 86%

- 1 release (4,400 insects) on tree island, which did not result in establishment -> 0%

- Total of 58,000 insects in Martin and Palm Beach counties

2009 releases- 63,000 insects in 10 releases (2000-15,000 insects each)

- Tree islands (x4), cypress (x2), oak hammock (x1), red bay/sawgrass scrub (x3)

- Palm Beach, Martin, Highlands, Monroe & Manatee counties

- Moths established at only 1 site (cypress) -> 10%

Factors impacting populations of the brown lygodium moth

1) Negative impacts of cold weather

Frost damage to lygodium, March 2009

a) At temperatures below 15 C (60 F), survival of the moth is reduced(75% survival at 27 C (81 F) down to only 25% at 15 C)

b) Freezing temperatures kill above-ground lygodium foliage-> destroys food supply causing starvation of the caterpillars

- Low temperatures may limit the utility of this agent in colder parts of FL

2) Attack by parasitoid wasps3.3 mm

2.0 mm 3.4 mm

Factors impacting populations of the brown lygodium moth

• At least six species of parasitoid wasp have been recovered so far • Parasitism rates were low during summer and fall 2008• By spring 2009, 25% of Neomusotima caterpillars were parasitized, and

emergence of moths had declined to 40%• Later in 2009, parasitism fell to 12%, & moth emergence recovered to 76%• Parasitism will be a key factor in the long-term success of this agent

Lygodium moth, Austromusotima camptozonale(Lepidoptera: Crambidae)

• Closely related to the brown lygodium moth, and larvae cause similar damage

• Native to subtropical Australia, so hoped that it may do better than the brown lygodium moth during Florida’s winter

• Plans to make new releases using fresh insect stocks later this year

Released in south Florida from 2005 to 2007, but did not establish

Lygodium sawfly, Neostromboceros albicomus(Hymenoptera: Tenthridinidae)

Currently undergoing regulatory evaluation by TAG & APHIS

• Native to Thailand & SE Asia

• Work started in 2005, but rearing problems halted project

• Thai cooperator discovered that mating requires large flight cages

• Larvae are leaf defoliators

Lygodium sawfly, Neostromboceros albicomus(Hymenoptera: Tenthridinidae)

• Host specificity testing completed 2009

• 38 fern species in 17 families

• 4 species relevant to FL (citrus, sugarcane, rice & cypress)

• 6 congeners– L. palmatum (native, American climbing fern)– L. japonicum (naturalized, invasive exotic weed)– L. cubense, L. venustum, L. volubile, L. oligostachyum

Lygodium sawfly, Neostromboceros albicomus(Hymenoptera: Tenthridinidae)

Results showed:• No significant feeding or oviposition on non-lygodium ferns or FL

species tested, nor any development to adult• No oviposition or development on L. palmatum• Low oviposition but no development on L. cubense & L. venustum• Comparable oviposition & some development (25%) on

L. japonicum, L. oligostachyum & L. volubile

- We hope to receive permission to release within the next 12 months

- The sawfly is not closely related to the lygodium moths--> we don’t expect it will suffer the same degree of parasitism

Lygodium stem-borers(Lepidoptera: Crambidae)

• 4 species recognized so far:I) Siamusotima aranea - Thailandii) Lygomusotima sp A - Singaporeiii) Lygomusotima sp B - Malaysian Borneoiv) Ambia sp - Hong Kong, Southern China

• Extremely small in size - adult wingspan = 9 mm (3/8 inch)- caterpillars = 5 mm (1/4 inch)

Under investigation at USDA Australian Biocontrol lab, Brisbane

Lygodium stem-borers(Lepidoptera: Crambidae)

--> Thought to have great potential for biocontrol

• Boring damage destroys vascular tissue and causes death of entire lygodium stem above the feeding point

• …but very difficult to rear

• Small size makes them hard to follow

• Although larvae have been successfully reared to adult, moths emerge at different times

• Host range testing will be started if rearing can be figured out

Conclusions• The brown lygodium moth is broadly established in Jonathan Dickinson

State Park, Martin County, FL and has successfully survived two winter seasons. Small moth population appears established in Loxahatchee NWR, Palm Beach County

• Caterpillars of the brown lygodium moth cause a 50 % reduction in lygodium ground cover when they first colonize an area, and these reductions appear to be maintained for at least the next 10-12 months beyond that

• Populations of the moth are adversely affected by cold weather during winter and are subject to attack and mortality by parasitoid wasps

• Key factor in determining long-term utility of the brown lygodium moth for lygodium biocontrol will be the extent to which parasitoid populations build-up and negatively impact populations of the moth

• Overall, results with the brown lygodium moth are encouraging, and we hope that other agents will make similar contributions to lygodium biocontrol

Acknowledgements

• Bob Pemberton (USDA-ARS retired)• Rachel Taylor, Gloria Witkus, (USDA-ARS)

• CSIRO Scientists at USDA Australia Biocontrol Lab, Brisbane

• Co-operators at Jonathan Dickinson State Park

Continuing funding from:• South Florida Water Management District• Florida Fish & Wildlife Conservation Commission

Citations

Boughton et al 2009. Laboratory host range testing of N. conspurcatalis…..Biocontrol Science & Technology. Vol 19, No. 4, p369-390

Boughton & Pemberton 2009. Establishment of Neomusotima conspurcatalis ….Biocontrol Science & Technology. Vol 19, No. 7, p769-772

Life cycle oflygodium sawfly

Eggs

Cocoon

Adult

Larvae

Subsequent releases used caterpillars reared in lab

Mating cage

Foliage bouquet

Upon emergence, caterpillars moved from bouquet onto lygodium foliage in sandwich boxes, ready for release