Biological Control of Tropical Soda Apple in Florida

Rodrigo Diaz

William A. Overholt

Stephen Hight

Amy Roda

Julio Medal

Ken Hibbard

Aquatic Weed Control

Short Course

May 7th, 2014

Arcadia, FL. Summer 2005

This talk covers the successful implementation of a biological control program of tropical soda apple

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1. Background of TSA 2. Biological control agent: Gratiana boliviana

3. Mass release program of beetles 4. Establishment and impact of beetles

Tropical soda apple (Solanum viarum) is a species of the nightshade family, Solanaceae

Shrub, perennial, up to 1.5m tall Leaves and stems covered with prickles

Racemes of white flowers Leaves are sticky due to trichomes

Tropical soda apple is a prolific seed producer

TSA can flower and fruit all year 400 seeds per fruit that remain viable in soil for 2 years (Mullahey 2002)

2 cm

Movement of TSA is facilitated by mammals, and the transport of contaminated hay and turf

Collier Co.

TSA has been reported in several states; however, it is a major problem only in Florida

also in

– Texas

– Mexico

Source: EDDMaps Source: EDDMaps October 2010 First report in Florida: 1988

TSA is invasive in open pastures as well as in shaded hammocks

DeSoto Co.

Dense TSA infestation disrupts cattle and wildlife movement Lack of shade increases heat stress in cattle

Alachua Co.

Florida ranchers lose $6.5 to 16 million annually due to increased control costs

Hendry Co.

Increased mechanical control Reduction in stocking rates Increased chemical control

St. Lucie Co.

TSA is an alternative host for insect pests and diseases of tomato, eggplant, pepper

Early blight (Alternaria)

Mosaic Virus

Colorado Potato Beetle

Tomato hornworm

Stink bugs

2. Biological control agent: Gratiana boliviana

Gratiana boliviana is a leaf feeding beetle found in Paraguay, Argentina and Brazil

30 days at 25oC

♀ ♂

Larvae and adults produce a ‘shot hole’ damage on the leaves

Larvae and adults feed voraciously on TSA leaves and wounds facilitate the entrance of diseases

Shot holes Skeletons

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.

Adults are reproductive from April to October and migrate to the ground during winter

Before the release of the beetle its host specificity was extensively studied under quarantine

Host range testing on 118 plants revealed that G. boliviana would only feed and reproduce on tropical soda apple

UF quarantine

Release Permit

SP1

SP2

SP3

SP 118

3. Mass release program of beetles

Mass rearing was conducted at several locations across Florida

DPI, Fort Pierce

USDA, Miami

UF, Gainesville

UF, Immokalee

This project was successful in part due to close collaboration of agencies

Releases targeted initially to counties with large TSA infestations

Okeechobee, Osceola, Highlands, Glades, St. Lucie

Source: National Agricultural Statistics Service, USDA

Releases were conducted by ranchers, extension agents and researchers

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4. Establishment and impact of beetles

After five year of releases, a survey was conducted to monitor the establishment and impact of beetles

38 counties with a total 113 of random sites Plant and beetle variables collected

Beetle densities were higher in St. Lucie and Okeechobee

Furthest beetles were found from a release site was 32.4 km

Average distance travelled / year = 4.7 km

Furthest distance travelled/year = 8.1 km

Highest density was 38 beetles per plant

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Height Diameter Fruit

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No GB

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Beetles negatively affected TSA performance

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B

A

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plant density

beetles/plant

Long term monitoring study revealed a decrease in TSA densities after 2 years of beetle release

Quarterly sampling of 16, 4 m2 quadrates

July 2006

October 2007

Before and after the beetle: St. Lucie Co.

July 2006

October 2007

Before and after the beetle: St. Lucie Co.

May 2003 June 2007

Before and after the beetle: Polk Co.

June 2005 August 2007

Before and after the beetle: Okeechobee Co.

July 2005

Survey of ranchers to assess the effectiveness of the program

Ranchers were more aware of the beetle in Central and South Florida

34%

71%

53%

2010

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62 55 53 51

55

North Florida Central Florida South Florida

Ranchers told us the beetle is helping at controlling TSA

How common are the beetle in the ranch? How is the level of success of these beetles?

54% of cattle owners in C and S-FL stated that the beetles were responsible for TSA control in their properties

Pamphlets, how-to manuals and videos used to communicate to a wider audience

Videos include the ‘rancher perspective’, ‘how to recognize beetles and plants’ and ‘how biological control works’.

Each step in the biological control program of TSA was crucial for the overall success

1. Recognition of impact of TSA 2. Availability of host specific agent

3. Effective release program

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4. Reduction in TSA densities in C and S-FL

Questions?