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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]

Lilioceris cheni is a successful biological control agent on the invasive yam, Dioscorea bulbifera in many areas in Florida, Georgia, Alabama and Louisiana. Two biotypes are available for release and come from significantly different centres of origin. The Nepalese biotype was collected at higher altitude and latitude sites, whereas the Chinese biotype was collected at slightly lower latitude and lower altitude. We hypothesised that Nepalese beetles would survive winter better in north Florida and that Chinese beetles would overwinter better in subtropical south Florida. We established sites in Homestead, Fort Pierce, Gainesville and Tallahassee, Florida to gauge the overwintering survival of each biotype. Beetles that overwintered in each site for one to three seasons were collected and followed to assess their reproductive capacity. In the final year of the experiment, we extracted fat bodies to determine effects of biotype and site. Nepalese beetles overwintered significantly better overall. Beetles survived better in the first study year (2013-2014). Both biotypes reproduced very well after surviving winter and beetles in Fort Pierce survived better than beetles in other regions and maintained a higher fat body. Nepalese beetles may have a wider ecological envelope - a decided advantage for a large region such as peninsular Florida. We suggest that current release programmes incorporate Nepalese beetles into their protocol to increase overwinter survival and establishment. [ABSTRACT FROM AUTHOR]

A Chinese biotype of Lilioceris cheni Gressitt and Kimoto (Coleoptera: Chrysomelidae) is being mass reared and released in Florida for biological control of the invasive air potato vine, Dioscorea bulbifera L. (Dioscoreales). Another biotype from Nepal is under investigation for determining whether its release would benefit the ongoing biological control program.We compared temperature-dependent development, fecundity, life table parameters, and consumption of the two biotypes in the laboratory. Both biotypes completed development at 20-30 °C, although survival of Chinese beetles was higher at 20 °C and 27.5 °C, and survival of Nepalese beetles was higher at 30 °C. In addition, Nepalese beetles developed at a faster rate at 20 °C, and consumed air potato foliage at a higher rate at 25 °C. The most important difference between the biotypes, with regard to biological control purposes, was the shorter generation time of Nepalese beetles, which resulted in a higher intrinsic rate of population increase, despite much higher fecundity of Chinese beetles. The higher intrinsic rate of increase of the Nepalese beetles may allow a more rapid population increase in the field, and thus, greater damage to air potato plants. However, differences in other life history traits, such as overwintering ability, diapause, and cold tolerance, will also influence field performance. [ABSTRACT FROM AUTHOR]

The yellowmargined leaf beetle, Microtheca ochroloma (Stal) (Coleoptera: Chrysomelidae), is an adventive pest of cruciferous crops in the southeastern United States. Despite its pest status, there is limited information about the influence of temperature on development and survival of M. ochroloma. The objectives of this study were to assess the effect of temperature on the development and survival of immature stages, and determine the cold tolerance of immature and adult stages. Development was evaluated at 15,20,25, and 30°C, and cold tolerance was measured at 5,0, and -5°C inside environmentally controlled chambers. Survival of M. ochroloma from egg to adult was ≈80% at 15,20, and 25°C, but only 24% at 30°C. Mean developmental time was longest at 15°C (57 d) and shortest at 30°C (17 d). Leaf area consumed by the fourth instar was 7.4-fold lower at 30°C compared with consumption at 15, 20, or 25°C. The lower developmental threshold varied from 7.3 to 9.8°C and the total degree-days required to complete development from egg to adult was 333. At 5,0, and -- 5°C, the LT90 values for the first instar were shorter compared with all other stadia, suggesting that the first instar is the most susceptible to cold temperatures. Eggs were most cold tolerant, followed by pupae and adults. Based on the LT50 (13d) and LT90 (38d) of eggs at 0°C, the predicted northern distribution of M. ochroloma extends to Kansas, Illinois, Kentucky, and Virginia. [ABSTRACT FROM AUTHOR]

Rising atmospheric CO2 levels could have drastic effects on the performance of invasive weeds and their insect herbivores. Despite the importance of biological control as an effective management tool for environmental weeds, there have been few studies on the potential impact of climate change on the future efficacy of biological control. The objective of the present study was to evaluate the effect of elevated CO2 on the performance of tropical soda apple Solanum viarum (Solanaceae) and its biological control agent Gratiana boliviana (Coleoptera: Chrysomelidae). We established three levels of CO2 in environmental growth chambers: ambient (400 ppm), medium (580 ppm) and high (780 ppm). Plants growing at the high level had greater biomass compared to those growing at the ambient and medium levels of CO2. Leaf water content and the amount of leaf nitrogen were reduced at high compared to ambient or medium CO2 levels. G. boliviana immature survival and developmental time were negatively affected at high CO2 but not at medium or ambient levels. Adults were lighter and smaller when reared at the high CO2 level compared to ambient and medium treatments, while adult fecundity was higher at the medium CO2 level. Leaf area consumed by fifth instars was lower when feeding on plants grown at the high CO2 level either inside a Petri dish or on potted plants. These results suggest that beetle performance may be diminished under future climate. However, further studies should incorporate other factors such as temperature and precipitation as well as the evolutionary potential of herbivores and plants to adapt to a changing climate. [ABSTRACT FROM AUTHOR]

Abstract: Tropical soda apple (TSA), Solanum viarum Dunal (Solanaceae), has invaded many pastures and natural areas in Florida. The biological control agent Gratiana boliviana Spaeth (Coleoptera:Chrysomelidae) is providing adequate control of TSA stands in South and Central Florida. However, poor or no establishment of this agent has occurred in northern Florida. The goal of this study was to examine the mortality factors that influence the population dynamics of G. boliviana in Florida. Horizontal life tables were constructed by following cohorts of individuals in the laboratory and inside closed and open cages at field sites in Central and North Florida. Fertility life table parameters were estimated using laboratory and field data. In addition, as part of a vertical life table analysis, TSA plants were sampled every two weeks in pastures in Central Florida, and counts of all G. boliviana and other herbivores and predators were recorded. Survival to adulthood was similar between Central and North Florida (open cages: 12–19%). Intrinsic mortality (laboratory data) and biotic factors (predation) together accounted for 75% of the mortality of immature stages. Survival of beetles in a natural population determined from vertical life tables was 5%. A complex of three mirid species (Engytatus modesta Distant, Tupiocoris notatus Distant, and Macrolophus sp.) were the most abundant predators found in the field, and are known to feed on G. boliviana eggs and larvae. Positive growth rates (r m =0.3) during the summer and early fall allow the beetle population to increase and provide suppression of TSA in Central Florida. [Copyright &y& Elsevier]

The effect of herbivory by Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) on the invasive, tropical soda apple (TSA) (Solanum viarum Dunal, Solanaceae), was investigated using exclusion methods and by monitoring the density of G. boliviana and the weed at four locations over a period of 40 months. TSA plants protected by insecticide were taller, wider, and had greater canopy cover that unprotected plants, and plants in closed cages were taller and wider than those in open cages. Survival of plants was higher in plots protected with insecticide than in unprotected plots in both years of a 2-year study. In the population dynamics study, the initial density of TSA was 4-5 times higher at one of the locations than at the other three sites, but within 3 years, TSA density at the high density site had declined by 90%. At the three sites which initially had a low abundance of TSA, density remained low throughout the study. The intrinsic rate of increase of G. boliviana varied between -3.9 and 4.5, but over the 3-year study, was not different from zero, indicating a stable population. The intrinsic rate of increase was lower than zero for the period from October to January, and greater than zero during the January to April period. In the periods from April to July and July to October, the rate of increase was not different from zero. The implications of these results for biological control of TSA in Florida are discussed. [ABSTRACT FROM AUTHOR]

The leaf beetle Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) was introduced from South America into the southeastern United States in 2003 as a classical biological control agent of tropical soda apple, Solanum viarum Dunal (Solanaceae). Temperature-dependent development and survival studies revealed that development was completed at temperatures >16°C and ≤34°C. The number of degree-days required to complete one generation was 341 and the estimated lower developmental threshold was 13.37°C. Using nonlinear regression, the upper lethal threshold was estimated to be 34-35°C. Cold tolerance studies revealed that the lethal time for 90% of adults (LT90) was 12.6 days at 5°C and 8.68 days at 0°C. Based on the developmental and cold tolerance data, a map predicting the areas of establishment and number of generations per year was generated, which suggests that the northern extent of the G. boliviana range in the USA will be near 32-33° north latitude. Fewer generations per year in more northern areas of the southeastern USA may decrease the effectiveness of this biological control agent. [ABSTRACT FROM AUTHOR]