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Air potato, Dioscorea bulbifera L. (Dioscoreaceae), is an invasive vine that climbs into vegetation outcompeting native species and altering ecosystems in the southeastern USA. The biological control agent, Lilioceris cheni Gressitt and Kimoto (Coleoptera: Chrysomelidae), has been released in Florida since 2011 and in other states including Georgia (2015), Louisiana (2016), Texas (2017), Mississippi (2018), and Alabama (2018) to manage air potato. Despite the wide distribution of the weed and mass rearing efforts, there are no studies documenting the establishment of L. cheni outside of Florida. The objectives of this study were to document the beetle release efforts by several agencies and determine the establishment and impact of L. cheni across the southeastern USA. Using community science reports and field surveys, we documented the distribution of air potato and L. cheni. Results demonstrated that the distribution of air potato extends to temperate regions from South Carolina and Georgia to subtropical regions of Louisiana, Texas, and Florida. Surveys showed that the beetle is present across all states with releases, and numbers fluctuated between 6 and 37 beetles counted per 30-surveyor-minutes. Most sites sampled had moderate to high beetle damage (scales of 3–4 out of 5), and air potato cover was low to moderate (2–3 out of 5). However, air potato was still abundant in some areas, which suggests the need for additional beetle releases and/or the use of other tactics to achieve management goals. [ABSTRACT FROM AUTHOR]

Multiple importations of Lilioceris cheni, a defoliating beetle of the invasive air potato plant, were received by the ARS-Invasive Plant Research Laboratory from 2002 to 2012. The last two, in 2011 (China) and 2012 (Nepal), formed the basis of two colonies from which releases were made into six Southeastern U.S. States. Colony populations were examined using the mitochondrial COI sequence. Phylogenetics, evolutionary divergence, a haplotype network, population statistics, and migration models were generated for the two colonies, countries of origin, and the inferred populations (clades). Phylogenetics eliminated the possibility of cryptic speciation and alleviated the need for host-range testing of the 2012 Nepalese samples. Evolutionary divergence showed the Chinese colony was 1.65X as divergent as the Nepalese, but one Nepalese clade was the most distinctly different of all clades. AMOVA showed most (>70%) genetic variation resided within rather than between colonies. In contrast, AMOVAs showed high levels (>61.5%) of genetic variation between underlying clades with proportionally less variation within. The haplotype network showed broad agreement with the phylogeny. Clade C, from China, displayed the largest number of haplotypes and the largest mutation-scaled effective population size in MIGRATE software. The best MIGRATE models indicated that migration and descent followed the order of phylogenetic descent. The results suggest that the genetic diversity being offered to the adventive range by these very divergent colonies (and clades) is large and should support great ecological flexibility. [ABSTRACT FROM AUTHOR]

Dioscorea bulbifera has invaded, smothered, and disrupted ecological functions of native plant communities in Florida. Vines senesce in late fall, then overwinter as tubers and aerial bulbils which sprout in spring and repeat the growth cycle. A foliage-feeding beetle Lilioceris cheni, introduced from Asia as a biocontrol agent has established throughout D. bulbifera's range in Florida. Synchronies among the growth phenology of the weed, life stages of biocontrol agents and weather conditions, are considered essential for the successful suppression of an introduced weed. We conducted a common garden study that encompassed pre-biocontrol release attributes of D. bulbifera followed by a 5-yr post-L. cheni release impacts study on its natural infestations in four sites. We gathered monthly data on D. bulbifera and L. cheni and assessed possible synchronies between their life stages and with local weather variables. Air and soil temperatures and total rainfall showed positive correlation with timing of D. bulbifera vine emergence/senescence, vine coverage, adult beetle emergence from diapause, and their life stages (egg clutches, larvae, and adults). Vine sprouting and beetle emergence in two southern sites began in February and April, and in the remaining two northern sites in March and May, respectively. Vine sprouting and beetle emergence was initiated at 15 and 20°C, respectively. All sites achieved maximum vine coverage in July. Bulbil development, oviposition by overwintering adults, and vine damage by adult and larval feeding began in June. These sequences of events indicated phenological synchrony of the beetle and air potato life stages in Florida. [ABSTRACT FROM AUTHOR]

Open-field host-specificity testing assesses the host-range of a biological control agent in a setting that permits the agent to use its full complement of host-seeking behaviors. This form of testing, particularly when it includes a no-choice phase in which the target weed is killed, may provide the most accurate assessment of the ecological host-range of an agent. We conducted a two-phase field host-specificity test with experienced and naïve adults of Lilioceris cheni Gressitt and Kimoto (Coleoptera: Chrysomelidae), a biological control agent of Dioscorea bulbifera L. (Dioscoreales: Dioscoreaceae). We followed field tests with a no-choice laboratory consumption study with the congeneric plant species that received test feeding in the field, and an additional field evaluation of spillover risk. Both experienced and naïve adults strongly preferred D. bulbifera to non-targets in the field. Within 47 h post-release, 90% of the released beetles that remained in the plots were found on D. bulbifera . In the laboratory no-choice test, the beetles consumed significantly more D. bulbifera and survived longer on this plant than the non-targets. All naïve beetles in the Dioscorea sansibarensis and Dioscorea villosa treatments and 75% of naïve beetles on Dioscorea floridana died within 7 d. Potted plants of the native D. floridana experienced minor test feeding in the spillover experiment when surrounded by large populations of L. cheni in the field. At the end of this experiment, L. cheni eggs and/or larvae were present on 83% of D. bulbifera plants but none of the D. floridana plants. We conclude that L. cheni is host-specific to D. bulbifera and does not pose a spillover risk to the native D. floridana . [ABSTRACT FROM AUTHOR]

Dioscorea bulbifera, an Asian vine, is invasive in the southeastern USA. It rarely flowers but propagates from potato-like bulbils formed in leaf axils, which persist into the subsequent growing season.Lilioceris cheniGressitt and Kimoto, a foliage-feeding beetle (Coleoptera: Chrysomelidae: Criocerinae) from Nepal, had been tested, proven to be a specialist and approved for release as a biological control agent. Regulatory delays, however, resulted in the demise of quarantine-held colonies, and acquisition of new Nepalese stock proved untenable. Searches then undertaken in southern China resulted in the collection of over 300 similar beetles. Two ChineseLiliocerisspecies were identified: one confirmed to beL. cheniand the other identified asLilioceris egena(Weise). Mitochondrial analysis revealed an exact DNA match between some Chinese and one of the two Nepalesecoxidase subunit I haplotypes and all ChineseL. chenihaplotypes clustered as a single species but the comingling of the two species aroused concerns over possible hybridisation. These concerns were allayed by nuclear D2 analysis showing the absence of dual parental sequences. Nonetheless, diligence was exercised to ensure that the Chinese strains were safe to release. Abridged host testing using critical test species verified specificity. Caged releases during autumn 2011 documented the ability of adult beetles to overwinter in south Florida despite a prolonged lack of foliage. Open releases the following year produced vigorous populations that caused extensive defoliation. Preliminary observations indicate thatL. cheninow contributes to the control ofD. bulbiferaand the bulbil-feedingL. egenashould complement these effects if its host range proves appropriate. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Biological control impact of L. cheni on D. bulbifera was studied in five sites for 5-year. • Feeding-damage by L. cheni killed premature D. bulbifera vines and freed smothered vegetation. • Lilioceris cheni population declined as the vine cover decreased in the sites. • Both quantity (density) and biomass of individual bulbils significantly decreased over years. • Lilioceris cheni will provide an ecologically and financially viable means for B. bulbifera management. Abstract Expanding populations of Dioscorea bulbifera , a trellising invasive vine of Afro-Asian provenance, have become widely established in the southeastern United States. Its clambering habit enables the weed to grow over, smother and displace native vegetation while producing vast quantities of vegetative propagules (bulbils) and reducing biodiversity of different ecosystems in Florida. A specialized foliage-feeding beetle, Lilioceris cheni from Nepal and China, has been released in USA for biological control of D. bulbifera. To determine the beetle's potential to curb the vine's ability to overtop native vegetation and to suppress propagule production, beetle restricted (insecticide treated) and unrestricted (beetle inoculated) sites were compared at five localities in Florida. Dioscorea bulbifera cover, L. cheni population density, and herbivore damage were documented at 6-week intervals, with bulbil density and biomass measured annually, for 5 years. Results from beetle unrestricted treatment revealed that high L. cheni feeding damage reduced vine cover over native vegetation, and decreased bulbil density and biomass. Spillover of L. cheni populations from beetle unrestricted into restricted treatment areas after exhaustion of D. bulbifera vines resulted in coalescing effects between treatments, so the beetle restricted treatment also showed some reduction in vine cover and bulbil density but individual bulbil biomass remained unchanged. These results show that L. cheni has the ability to suppress the invasive attributes of D. bulbifera in its adventive range. [ABSTRACT FROM AUTHOR]