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Simple Summary: Privets (Ligustrum spp.) are popular hedge shrubs that escape from gardens and cause negative impacts by invading forests in the United States. The narrow host specificity of the seed-feeding weevil, Ochyromera ligustri, suggests that this weevil could be considered a fortuitous biological control agent of privets. To find out the host range of this weevil, time-consuming experiments involving rearing and dissections are often conducted. Herein, we developed PCR primers to rapidly and accurately detect the presence of the weevil in privet fruits. We confirmed that the novel PCR primers specifically work for O. ligustri even with a small quantity of DNA, which was 0.01 ng. Using the newly developed PCR-based detection saves time and labor in research related to the detection and impact of this weevil. Ligustrum spp. (Oleaceae) have become invasive species in the US and negatively affect native plant diversity and richness in forests. Ochyromera ligustri (Coleoptera: Curculionidae) is considered a potential biological control agent in the US because adults feed on the foliage and larvae are seed-feeders of Ligustrum spp. To discover the relationships between O. ligustri and Ligustrum spp., fruit dissections or rearing and field observations are required. In the current research project, novel PCR primers were developed to rapidly detect the DNA of O. ligustri in molecular analyses without rearing and observation. The developed PCR primers worked even with 0.01 ng of DNA and did not amplify the DNA of the other five curculionid species tested. When the novel primers were tested with three Ligustrum spp. species common in the southeastern US, the DNA of O. ligustri was detected from all three species. We expect that the novel primers will be utilized to find out the presence and impact of O. ligustri on Ligustrum spp rapidly and accurately. [ABSTRACT FROM AUTHOR]

Invasion from giant salvinia (Salvinia molesta Mitchell, Salviniaceae) blocks sunlight entering waterbodies, reducing submerged aquatic macrophytes, thus lowering dissolved oxygen and stressing aquatic organisms. Due to its rapid growth and ease of dispersal through fragmentation, giant salvinia can quickly become problematic and difficult to eradicate. Since invasion of giant salvinia is persistent, land managers need a cost-effective method of control. Biological control by the salvinia weevil (Cyrtobagous salviniae Calder and Sands, Coleoptera: Curculionidae) has proven successful in controlling giant salvinia, and at a fraction of the cost of chemical and mechanical control. To maintain a source of salvinia weevils for field releases, mass rearing in outdoor ponds by natural resource managers is common practice in tropical regions. Using number of freezing hours and degree-day calculator, we examined how winter and spring conditions impacted the production of weevils in mass rearing ponds across southern Louisiana, USA. We found that winter temperature determined adult weevil mortality while spring temperature dictated reproduction, larval appearance, and timing of pond harvest. During winters with <55 h of freezing temperatures, ponds maintained densities of at least 13 adult salvinia weevils kg−1. Winter with >200 hours of freezing temperature reduced adult density in the ponds nearly extirpating the population. Larvae were found on samples on average at 89 degree-days which began accumulating in January 1st. This study suggested that winter and spring conditions are critical for mass rearing operations and population growth of C. salviniae. [ABSTRACT FROM AUTHOR]

Brazilian peppertree,Schinus terebinthifoliaRaddi (Anacardiaceae), is a South American plant that is highly invasive in Florida. The impact of insect herbivores on the performance of Brazilian peppertree was evaluated at two locations in Florida using an insecticide exclusion method. Although 38 species of insect herbivores were collected on the invasive tree, there were no differences in growth or reproductive output of insecticide protected and unprotected trees, providing evidence that insect feeding had no measurable impact on tree performance. The majority of insects collected on Brazilian peppertree were generalists, and several were serious agricultural pests. [ABSTRACT FROM PUBLISHER]

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]

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]

Simple Summary: Mismatched distributions between biological control agents and their host plants occur for a variety of reasons but are often linked to climate, specifically differences in their low-temperature tolerances. How to measure and use low-temperature tolerances of control agents to inform agent prioritization, selection for redistribution, or predict efficacy is vitally important, but has not been previously synthesized in a single source. We discuss causes of climate mismatches between agents and target weeds, the traditional and non-traditional approaches that could be used to decrease the degree of mismatch and improve control, and regulatory issues to consider when taking such approaches. We also discuss the variety of cold tolerance metrics, their measurement and ecological value, and the types of modeling that can be carried out to improve predictions about potential distributions of agents. We also briefly touch on molecular bases for cold tolerance and opportunities for improving cold tolerance of agents using modern molecular tools. Many weed biological control programs suffer from large-scale spatial variation in success due to restricted distributions or abundances of agents in temperate climates. For some of the world's worst aquatic weeds, agents are established but overwintering conditions limit their survival in higher latitudes or elevations. The resulting need is for new or improved site- or region-specific biological control tools. Here, we review this challenge with a focus on low-temperature limitations of agents and propose a roadmap for improving success. Investigations across spatial scales, from global (e.g., foreign exploration), to local (selective breeding), to individual organisms (molecular modification), are discussed. A combination of traditional (foreign) and non-traditional (introduced range) exploration may lead to the discovery and development of better-adapted agent genotypes. A multivariate approach using ecologically relevant metrics to quantify and compare cold tolerance among agent populations is likely required. These data can be used to inform environmental niche modeling combined with mechanistic modeling of species' fundamental climate niches and life histories to predict where, when, and at what abundance agents will occur. Finally, synthetic and systems biology approaches in conjunction with advanced modern genomics, gene silencing and gene editing technologies may be used to identify and alter the expression of genes enhancing cold tolerance, but this technology in the context of weed biological control has not been fully explored. [ABSTRACT FROM AUTHOR]

• Biotic and abiotic influences on weed biological control vary geographically. • Literature and a global database on weed biological control were reviewed. • Abiotic limitations such as temperature and precipitation were most common. • Biogeographical studies will inform predictions and manage control expectations. The impacts of different biotic and abiotic limiting factors on introduced biological control agents and their weed targets may result in geographically variable control, with implications for ongoing management and plans to improve efficacy. Geographic variability in control successes, however, may be underreported. Using the comprehensive catalogue, "Biological control of weeds: A world catalogue of agents and their target weeds", we assessed whether geographic variability in successful control is common, whether variability in programs could be attributed to limiting factors, and which factors were most likely responsible for variable success. In 38% of all reviewed programs, success was deemed spatially variable but nearly half of variable programs had unknown or unreported limiting factors. We discuss the factors that can contribute to geographic variability in agent abundance and associated success of weed biological control, provide case studies and current biological control practices, and finally discuss the potential ecological and evolutionary consequences of this variability. Published data to assess whether geographic patterns of variability were predictable, or to quantify variability along environmental gradients are lacking. Research that addresses the strength of agent-host interactions across environmental gradients, such as temperature or precipitation, or examines spatial variability in a metapopulation or landscape context may provide the best understanding of control failures and contribute to a biogeographic framework within which to evaluate ongoing and future biological control projects. [ABSTRACT FROM AUTHOR]

Schinus terebinthifolia (Brazilian Peppertree) is a South American plant that has become invasive in many countries around the world. It was introduced into the US about 100 years ago as an ornamental. Escaping cultivation, it now occurs in Alabama, Florida, Georgia, Texas, California, and Hawai’i. This species is one of the most invasive weeds threatening agriculture and natural areas in the Southeast. Efforts to manage Brazilian Peppertree populations with biological controls began in Hawai’i in the 1950s and resulted in the release of 3 insect species. However, the control agents have had minimal impact, and the weed continues to be a difficult problem. More recently, our international team of collaborators has discovered and tested numerous new species of potential biological control agents. These species attack different plant tissues and include defoliators, sap-suckers, stem borers, and leaf- and stem-gall formers. Despite difficulty finding an agent sufficiently specific for field release in Florida, we have narrowed the field to 2 promising species, the thrips Pseudophilothrips ichini (Hood) and the foliage-gall former Calophya latiforceps Burckhardt. Results of no-choice and choice trials conducted overseas and in quarantine indicate that both species will safely contribute to the control of this invasive weed. Herbivorous feeding by immature and adult individuals of both herbivore species stunt growth, distort leaves, and should reduce reproductive output of Brazilian Peppertree. [ABSTRACT FROM AUTHOR]