Stephen D. Hight

Biological Control of Purple LoosestrifeA case for using insects as control agents, after rigorous screening, and for integrating release strategies with research

P urple loosestrife (Lythrum salicaria L.) is an exotic wetland perennial responsible for the degradation of many prime wetland habitats throughout the temperate regions of the United States and Canada. Large, monotypic stands reduce the biotic diversity of wetland systems by replacing native plant species (Stuckey 1980) and thereby eliminating the natural foods and cover essential to many wetland wildlife inhabitants, including waterfowl (Friesen 1966, Rawinski and Malecki 1984, Smith 1964). In North America, this plant is a classic example of an introduced species whose distribution and spread has been enhanced by the absence of natural enemies and the disturbance of natural systems, pri-

Biology, host specificity tests, and risk assessment of the sawfly Heteroperreyia hubrichi, a potential biological control agent of Schinus terebinthifolius in Hawaii

Heteroperreyia hubrichiMalaise (Hymenoptera: Pergidae), a foliagefeeding sawfly of Schinusterebinthifolius Raddi (Sapindales:Anacardiaceae), was studied to assess itssuitability as a classical biological controlagent of this invasive weed in Hawaii. No-choice host-specificity tests were conductedin Hawaiian quarantine on 20 plant species in10 families. Besides the target weed, adultfemales oviposited on four test species. Females accepted the Hawaiian native Rhussandwicensis A. Gray (Sapindales:Anacardiaceae) as an oviposition host equallyas well as the target species. The other threespecies received significantly fewer eggs. Neonate larvae transferred onto test plantssuccessfully developed to pupae on S.terebinthifolius (70% survival) and R.sandwicensis (1% survival). All other 18test plant species failed to support larvaldevelopment. A risk analysis was conducted toquantify the acceptability of non-targetspecies as host plants for H. hubrichi onthe basis of the insects performance atvarious stages in its life cycle. Risk ofdamage to all plant species tested wasinsignificant except for R. sandwicensis. Risk to this native plant relative to S.terebinthifolius was estimated at 1%. Currently this level of risk is too high torequest introduction of this insect into theHawaiian environment. Detailed impact studiesin the native range of S. terebinthifoliusare needed to identify thepotential benefit that this insect offers. Also, field studies in South America withpotted R. sandwicensis would give a morereliable analysis of the risk this nativeHawaiian plant would face from naturalpopulations of H. hubrichi.

RELEASES, DISTRIBUTION AND ABUNDANCE OF GRATIANA BOLIVIANA (COLEOPTERA: CHRYSOMELIDAE), A BIOLOGICAL CONTROL AGENT OF TROPICAL SODA APPLE (SOLANUM VIARUM, SOLANACEAE) IN FLORIDA

ABSTRACT From 2003 to 2008, 176,643 Gratiana boliviana, Spaeth (Coleoptera: Chrysomelidae) were released in Florida as part of a biological control program targeting tropical soda apple (TSA) Solarium viarum Dunal (Solanaceae). The spatial distribution of releases was clustered with more beetles released in south/central Florida than further north. A survey conducted in the fall of 2008 found G. bolviana present at >70% of randomly selected locations between 26° and 29° latitude, but no beetles were found at sites further north. The presence of beetles and beetle damage were associated with smaller TSA plants and fewer fruits per plant. The absence of beetles in northern Florida may be due to the fewer number released in that area, but also could be influenced by land cover and climate.

Host specificity tests of Galerucella calmariensis (L.) and G. pusilla (Duft.) (Coleoptera: Chrysomelidae), potential biological control agents of purple loosestrife, Lythrum salicaria L. (Lythraceae)

Abstract Host specificity tests of Galerucella calmariensis (L.) and Galerucella pusilla (Duft.) (Coleoptera: Chrysomelidae) were conducted under quarantine to determine the suitability of these beetles as biological control agents of purple loosestrife, Lythrum salicaria L., an aggressive emergent aquatic weed of Eurasian origin. Both species of imported Eurasian beetles, natural enemies of purple loosestrife, were tested on 15 species of plants from nine families within six orders. The plants were selected on the basis of preliminary tests by the Commonwealth Agricultural Bureaux International Institute of Biological Control. Adult G. calmariensis readily fed and oviposited on Lagerstroemia indica L., Decodon verticillatus (L.) Ell., and Lythrum alatum Pursh. However, only L. alatum and Lythrum virgatum L., besides the target host purple loosestrife, supported larval development beyond the first instar to the adult stage. Test plants outside the Lythraceae showed minimal feeding or oviposition and were not suitable as hosts. Feeding by adult G. pusilla was confined to members of the Lythraceae. Of the five test plants that were accepted for oviposition, only two (L. virgatum and L. alatum) were suitable for larval development past the first instar. As L. virgatum is considered taxonomically similar to L. salicaria, it appears that the only test plant that is a suitable host for both Galerucella spp., besides the target plant, is L. alatum. These results suggest that both species of beetles are highly host specific and should not be a threat to nontarget plants with the exception of L. alatum.

Host specificity tests of Hylobius transversovittatus goeze (Coleoptera: Curculionidae), a potential biological control agent of purple loosestrife, Lythrum salicaria L. (Lythraceae)

Abstract Host specificity tests of Hylobius transversovittatus Goeze (Coleoptera: Curculionidae) were conducted under quarantine to determine the suitability of this imported Eurasian weevil as a biological control agent of purple loosestrife, Lythrum salicaria L., an emergent aquatic weed of Eurasian origin. Based on preliminary tests by the C.A.B. International Institute of Biological Control (IIBC), 15 species of plants from nine families were selected for the tests. Adult feeding, oviposition, and larval development of the weevil were restricted to the family Lythraceae. Besides purple loosestrife (the target plant), Decodon verticillatus (L.) Ell. supported larval development to the adult stage. Lythrum alatum Pursh. supported larval development to the third instar. There was, however, more adult feeding and ovipositional preference for purple loosestrife over all other test species. The results suggest that H. transversovittatus is adequately host specific and should not be a threat to nontarget plants.

Pheromone-Based Attractant for Males of Cactoblastis cactorum (Lepidoptera: Pyralidae)

Abstract The cactus moth, Cactoblastis cactorum (Berg), is an invasive pest of Opuntia spp. Since its arrival in the Florida Keys in 1989, it has moved rapidly up the east and west coasts of Florida, threatening to invade the southwestern United States and Mexico. Female moths produce a sex pheromone that attracts male moths. In this study, we report on mating behavior observed in the laboratory and the identification of putative pheromonal chemical components based on mass spectral analysis of volatiles collected from virgin female moths and from solvent extraction of excised glands. Three candidate components, formulated on rubber septa in different release rates and ratios, were tested in laboratory olfactometer and flight tunnel experiments, and in field tests in areas with known feral populations of cactus moths. Lures formulated with the three-component blend of 54% (Z,E)-9,12 tetradecadien-1-ol acetate, 42% (Z,E)-9,12 tetradecadien-1-ol, and 4% (Z)-9- tetradecen-1-ol acetate were the most effective, although changes in the ratio of these components had little effect on lure efficacy. For field deployment, traps baited with synthetic lures with a 1 mg load of the three component blend captured equal or higher numbers of males than traps baited with two virgin females. Trapping systems using this pheromone-based attractant will be useful for population delineation in areas currently infested.

Oviposition preference of Cactoblastis cactorum (Lepidoptera: Pyralidae) in caged choice experiments and the influence on risk assessment of F1 sterility

Abstract Releases of lepidopteran biological control agents have successfully controlled invasive weed species. However, issues with non-target effects of released exotic agents have resulted in stringent pre-release host specificity testing. Use of inherited (F1) sterility, a radiation induced genetic condition that can cause sterility in the F1 generation, could further assess the risk of non-target effects and negative ecological effects under field conditions. This technique may aid in approving potentially effective and safe biological control agents for release. The unintentional arrival of the cactus moth, Cactoblastis cactorum, into the United States provides a unique opportunity to evaluate the potential of F1 sterility. This study was conducted to assess host oviposition preferences of C. cactorum females mated with irradiated and non-irradiated males for cactus species from seven groups based on location, cactus growth characteristics (plant structure), spine densities, genera, and economic importance. No significant differences in female host preference were observed between females mated with normal or irradiated males. Lack of significant differences in oviposition preference suggests that inherited (F1) sterility has potential as a risk assessment tool for potential exotic biological control agents for invasive weed species. Evaluation of the overall analysis of female C. cactorum host preference revealed that significantly different numbers of eggsticks were oviposited on cactus species. In whole plant cages, significantly more eggsticks were oviposited on Opuntia corallicola than any other species, and in cladode cages, significantly more eggsticks were oviposited on Opuntia humifusa than all other species except Opuntia pusilla.

BIOLOGICAL CONTROL OF TROPICAL SODA APPLE (SOLANACEAE) IN FLORIDA: POST-RELEASE EVALUATION

Dunal (Solanaceae) were con-ducted initially in 1994 by University of Floridaresearchers in collaboration with UniversidadeEstadual Paulista, Jaboticabal campus, Brazil.Sixteen species of insects were found associatedwith tropical soda apple in Brazil and Paraguay(Medal et al. 1996). A biological control programwas initiated by the University of Florida in 1997with funds provided by the United States Depart-ment of Agriculture, Animal and Plant Health In-spection Service, and the Florida Department ofAgriculture & Consumer Services. Explorationsin the place of origin (southern Brazil, northeastArgentina, south Paraguay, and Uruguay) of thetarget weed were conducted in collaboration withBrazilian university researchers, and the USDA-Agriculture Research Service Biological ControlLaboratory in Hurlingham, Argentina. During ex-ploratory surveys, the leaf beetle

Release and distribution of Lilioceris cheni (Coleoptera: Chrysomelidae), a biological control agent of air potato (Dioscorea bulbifera: Dioscoreaceae), in Florida

ABSTRACT From 2012 to 2015, 429,668 Lilioceris cheni Gressit and Kimoto (Coleoptera: Chrysomelidae) were released in Florida for biological control of air potato Dioscorea bulbifera L. (Dioscoreaceae). In the fall of 2015, a state-wide survey was conducted at 113 randomly selected air potato infestations in order to determine the spatial distribution of L. cheni. Damage due to L. cheni was found at 86% of locations and was low in the Florida panhandle where air potato was relatively uncommon and fewer beetles had been released, and in far south Florida, despite high numbers of beetle releases. On average, beetles travelled 9.5 km from the nearest release site to survey sites from the date of release to the time of the survey, with a maximum distance of nearly 67 km. The rate of spread was estimated at 8.2 km/year under the assumption that beetles present at survey sites migrated or were moved from the nearest release site. Air potato vines produced fewer aerial tubers, the vegetative propagule of air potato, as foliar damage due to L. cheni increased. The results suggest that future research efforts should focus on determining the biotic and abiotic factors that may be limiting establishment in some areas of Florida.

Opportunities for improving risk communication during the permitting process for entomophagous biological control agents: a review of current systems

Concerns about potentially irreversible non-target impacts from the importation and release of entomophagous biological control agents (BCAs) have resulted in increasingly stringent national import requirements by National Plant Protection Organizations worldwide. However, there is a divergence of opinions among regulators, researchers, environmentalists, and the general public on ways to appropriately manage associated risks. Implementation of a comprehensive and effective risk communication process might narrow the opinion gaps. Results from a comprehensive survey conducted in the United States were used to describe communication habits of stakeholders involved in biological control and identify areas that are fundamental in an efficient process. In addition, this study critically reviews risk communication practices and how phytosanitary decisions are communicated in the permitting systems for entomophagous BCAs of several countries to identify risk communication tools used in an effective risk communication framework. The following barriers to efficient risk communication were identified: absence of a formalized risk communication process, undefined risk communication goals and target audiences, lack of credibility and objectivity of information sources, inefficiency of mode of distribution of messages, insufficient public participation, and lack of transparency of decision making processes. This paper suggests the creation and/or enhancement of modes of distribution of risk messages to increase coverage, understanding, and guidance. For instance, messages should be presented in different formats such as internet, brochures, and newspapers. Surveys, public meetings, and trainings/workshops are tools that can be used to characterize stakeholders’ diversity and develop risk messages specific to the targeted audience. Implementation of a participatory decision making process will increase stakeholder involvement and trust in the risk management plan. Development of practical mechanisms, such as public hearings will increase all stakeholders’ involvement in the risk assessment process. A clear framework describing how public comments will be incorporated in the decision making process should be implemented. Finally, to ensure a streamlined risk communication process, there must be consistency in the messages disseminated by federal, state, and local agencies.