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Tropical soda apple (Solanum viarum Dunal) (Solanaceae) is a small shrub native to South America that is invasive in pastures and conservation areas across Florida. Dense patches of tropical soda apple not only reduce cattle stocking rates and limit their movement, but also serve as reservoirs for pests of solanaceous crops. A classical biological control program was initiated in 1994 with exploration for natural enemies of tropical soda apple in Argentina, Brazil, and Paraguay. Host specificity tests conducted under laboratory and field conditions demonstrated that the leaf feeding beetle Gratiana boliviana Dunal (Coleoptera: Chrysomelidae) was a specialist herbivore that completes development only on the target weed. After obtaining appropriate permits, field releases of G. boliviana were initiated in Florida in May of 2003. Larvae and adults of G. boliviana feed on tropical soda apple leaves and may completely defoliate their host plants, resulting in reduced growth and fruit production. Mass rearing facilities for the beetle were established in northern, central and southern Florida, and adults were either hand-carried or transported to release sites by overnight courier. From 2003 to 2011, a total of 250,723 beetles were released and they became established throughout Florida, however, their impact is more noticeable in regions below latitude 29 °N. Reductions of tropical soda apple densities caused by damage by the beetle were visible 2-3 yr after initial release, or in some cases, within a few months. Various methods of technology transfer were used to inform the public, land owners, funding agencies and scientists about the biological control program, including articles in trade magazines, extension publications, websites, videos, field days and scientific publications. The project was successful because of the coordinated efforts of personnel from federal, state and county agencies.

Survival assays were conducted with beet armyworm (BAW), Spodoptera exigua (Hubner), a tortoise beetle, Gratiana bolivana Spaeth, and western flower thrips (WFT), Frankliniella occidentalis (Pergande), on tropical soda apple (TSA), Solanum viarum Dunal, a relative of tomato. Both S. exigua and G. boliviana seem to induce plant defenses in tropical soda apple. Significantly more S. exigua neonate larvae survived to second instar on non-induced plants and artificial diet when compared with plants with induced defenses. Our results further suggest that the induced response in TSA was systemic, since BAW neonates suffered higher mortality in induced plants despite not being in direct contact with the damaged part of the plant. Results suggested that feeding action of G. boliviana on TSA had no significant influence on WFT host choice.

Multiple-choice and no-choice tests were conducted at the Florida Department of Agriculture quarantine facility to determine the host specificity of the South American flower bud weevil, Anthonomus tenebrosus Boheman, intended for biological control of the exotic weed tropical soda apple (TSA), Solanum viarum Dunal in Florida, USA. Ninety-one plant species in 21 families were included in multiple-choice feeding and oviposition experiments, including the target weed and the 6 major cultivated Solanaceae: bell pepper (Capsicum annuum L.), chili pepper (C. frutescens L.), tomato (Lycopersicon esculentum Mill.), tobacco (Nicotiana tabacum L.), eggplant (Solanum melongena L.), and potato (Solanum tuberosum L.). Plant bouquets with flower-buds of 8 to 10 randomly selected plant species, always including TSA (S. viarum) were exposed to 10–20 A. tenebrosus adults for 1 to 2 weeks. Oviposition and feeding were observed twice a week. No-choice host-specificity tests were also conducted with A. tenebrosus a...

Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae), the first biocontrol agent introduced against tropical soda apple, Solanum viarum Dunal (Solanaceae), was released in Florida in the summer 2003. Post-release evaluations have focused on insect population changes and the impact of insect feeding damage on the plant defoliation and fruit production of the target weed. Gratiana boliviana quickly established in the release sites, and dispersed causing extensive defoliations to tropical soda apple plants and significant reduction of fruit production. Plant defoliation during the first growing season was directly associated with the increase in number of beetles observed on the tropical soda apple plants. Beetles showed a dispersal ability from the release sites of 1.6 km per year. Two years after the beetle release, most of the tropical soda apple plants at the 3-ha release site in Polk County and at the release site in Okeechobee County, Florida have been replaced by other plant species, resulti...

Open field experiments were conducted in Brazil to assess the suitability of the South American leaf feeding beetle Metriona elatior Klug for biological control of tropical soda apple, Solanum viarum Dunal in the USA. A multiple choice open field test with eggplant (Solanum melongena L.), bell-pepper (Capsicum annuum L.), potato (Solanum tuberosum L.), tomato (Lycopersicon esculentum Mill.), gilo (Solanum gilo Raddi), falsa-jurubeba (Solanum fastigiatum Willd.), and the target weed Solanum viarum, was conducted at the Universidade Federal do Parana Experimental Station in Curitiba. A second multiple choice-test was conducted 2 years later at the same location excluding the target weed and exposing M. elatior adults to S. melongena, S. tuberosum, L. scullentum, and C. annuum. An S. viarum control plot was established 60 km from the choice-test field. In total, 276 teneral adult beetles were released in the first multiple choice-test. In the second test, 176 beetles were released in the choice-test...

An open-field experiment was conducted to assess the suitability of the South American leaf feeding beetle Gratiana boliviana Spaeth for biological control of Solanum viarum Dunal in the USA. An open-field test with eggplant, Solanum melongena L., was conducted on the campus of the University of Buenos Aires, Argentina, and a S. viarum control plot was established 40 km from the campus. One hundred adult beetles were released in each plot at the beginning of the experiment during the vegetative stage of the plants, and forty additional beetles were released in the S. melongena plot at the flowering stage. All the plants in each plot were checked twice a week and the number of adults, immatures, and eggs recorded. Results showed almost a complete rejection of eggplant by G. boliviana. No noticeable feeding damage was ever recorded on eggplant. The experiment was ended when the eggplants started to senesce or were severely damaged by whiteflies and spider mites. The results of this open-field exper...

Solanum mauritianum Scopoli and Solanum sisymbriifolium Lamarck are major exotic weeds in South Africa, while Solanum viarum Dunal is similarly problematic in the United States of America. All three species are native to northeastern Argentina and southeastern Paraguay, where they were surveyed for natural enemies in February 1998. Insect agents for Solanum weeds have a tendency to extend their host ranges to include non-target Solanum species, in particular cultivated eggplant (S. melongena L.), during laboratory trials, making it difficult to promote their release. To facilitate the interpretation of such results, other native and cultivated Solanum species that grew in close proximity to the target species were also surveyed to give an indication of the insects’ field host ranges. During the survey period, 19 insect herbivore species were recorded on S. mauritianum, while 8 species were recorded on each of S. sisymbriifolium and S. viarum. Based on the insects’ occurrence, abundance and damage...

The larval developmental rate of the tortoise beetle Metriona elatior Klug (Coleoptera: Chrysomelidae), a potential biocontrol agent of tropical soda apple (TSA) Solanum viarum Dunal (Solanaceae), was studied in the laboratory at 3 constant temperatures (20[degree], 25[degree], and 30[degree]C), photoperiod (14:10 L: D), and relative humidity 60%- 80% in growth chambers. Sixteen neonate larvae were individually reared on excised TSA leaves placed in 0.5-liter transparent-plastic containers for each temperature treatment. Larvae were daily checked to determine the number and duration of larval instars at each of the temperature tested. At 20[degrees] and 25[degree]C, the percent survival from first instar to adult was 75 and 73%, respectively. A constant temperature of 30[degrees]C had a detrimental effect on the larvae and none reached the pupa/adult stages. The general life cycle of this beetle is discussed.

Survival assays were conducted with beet armyworm Spodoptera exigua (Hubner) and southern armyworm S. eridania (Stoll) with tropical soda apple Solanum viarum Dunal, a relative of tomato. In addition, polyphenol oxidase (PPO) enzyme assays were conducted to determine if plant defense compounds are being produced by tropical soda apple in response to herbivory. Both S. exigua and S. eridania induced plant defenses in tropical soda apple. Significantly more S. exigua and S. eridania neonate larvae survived to 2nd instar on non-induced plants and artificial diet when compared with plants with induced defenses. Tropical soda apple plants fed on by S. exigua and S. eridania had significantly increased PPO activity.