Response of Chinese Tallow (Triadica sebifera) and Coexisting Natives to Competition, Shade, and Flooding

A greenhouse experiment was designed to determine the interactive effect of light, flooding, and competition on the growth and performance of Chinese tallow (Triadica sebifera [L.] Roxb.) and three tree species native to the southeastern United States: water tupelo (Nyssa aquatica L.), sugarberry (Celtis occidentalis L.), and green ash (Fraxinus pennsylvanica Marshall). The experiment used a factorial design that received two treatments: light (low irradiance or high irradiance) and flood (nonflooded and flooded) regimes. In the nonflooded and high irradiance treatment, changes in the growth (ground diameter, number of leaves, and total biomass) indicated that growth metrics of tallow were highest when growing with sugarberry and water tupelo but decreased when tallow was in competition with green ash. In contrast, competition with tallow reduced the height, net photosynthetic rate, stomatal conductance, and transpiration rate of water tupelo. The results showed that tallow had lower growth metrics when in competition with green ash at no apparent decrease in the growth of green ash except for growth rate. Our results suggest that tallow may be less competitive with certain native species and underplanting may be a possible opportunity for improving the success rates of native trees species establishment in areas prone to tallow invasion. Study Implications: Chinese tallow is a highly invasive tree species in the southeastern coastal states and in this study, we examined the growth and survival of tallow in competition with tree species native to the southeastern coastal states, USA. The growth of tallow differed greatly among native species in well-drained environments lacking forest overstory with lower growth metrics when grown with green ash but higher growth metrics when grown with water tupelo and sugarberry. Following density reduction treatments, we recommend management actions that promote the regeneration of native tree species to occupy the open vegetation canopy and suppress reestablishment of tallow.

Host Plants of the Immature Stages of the Invasive Longan Lanternfly, Pyrops candelaria (L.) (Hemiptera, Fulgoridae) in Taiwan

The longan lanternfly, Pyrops candelaria (L.), has been invading mainland Taiwan since 2018, but the distribution of the species has been confined to northern Taiwan until now. The manual removal of the adult insects from the longan is still the main control strategy because of the uncertainty around other key host plants, especially for eggs and nymphs. In this study, large numbers of eggs and nymphs were found on Triadica sebifera (L.) Small and Acacia confusa Merr. The occurrence of immature individuals on Triadica sebifera increased with developmental stage from eggs to the last instar from May to July 2021. On April 30, the first egg mass was recorded. More egg masses were recorded in May, and some could be found in July. In May, only two younger instars were detected. Third and fourth instars began to appear from June, while the fifth instar was mainly recorded from July onwards. The results of this study provide great strategic value for decision-makers to allow for effective control of the target tree species. For now, we proved that longan and pomelo trees, preferred by adults, are not the key hosts for the immature stages of this insect, because few immature individuals were found on them. Therefore, we suggest that the existence of Triadica sebifera should be considered when analyzing possible spreading areas of this invasive lanternfly in Taiwan.

Spatiotemporal Invasion Severity of Chinese Tallow (Triadica sebifera) and Invasibility of Forest Types in Southern US Forestlands

Quantifying invasion severity of nonnative invasive plant species is vital for the development of appropriate mitigation and control measures. We examined more than 23,250 Forest Inventory and Analysis (FIA) plots from the southern coastal states of the United States to develop an alternative method to classify and map the invasion severity of Chinese tallow (Triadica sebifera). Remeasured FIA plot-level data were used to examine the spatiotemporal changes in the presence probability and cover percentage of tallow. Four invasion severity classes were identified by using the product of presence probability and cover percentage. Chinese tallow invasion severity increased over time with 90 and 123 counties being classified into the highest severity class for the first and second measurement, respectively. Further, the invasibility of major forest-type groups by severity class was examined using the product of the county-level mean presence probability and mean cover percentage of Chinese tallow as a proxy of invasibility. Longleaf/slash pine (Pinus palustris/P. elliottii) forests were highly resilient to the Chinese tallow invasion. In contrast, elm/ash/cottonwood (Ulmus spp./Fraxinus spp./Populus deltoides) and oak/gum/cypress (Quercus spp./Nyssa spp./Taxodium spp.) forest-type groups were vulnerable to invasion. Study Implications: In the southern United States forestland, differences in invasion severity and vulnerability of forest types to Chinese tallow invasion have been observed across time and space. Our findings provide insight into spatial variations in the severity of Chinese tallow invasion and the relative susceptibility of different forest-type groups in the region to inform monitoring and management of this invasive species. High invasion severity occurs in the lower Gulf of Mexico coastal region of Texas, Louisiana, and Mississippi and the Atlantic coastal region of South Carolina and Georgia, with the longleaf/slash pine and oak/gum/cypress forest-type groups being most susceptible to Chinese tallow invasion. Based on these results, we recommend that management efforts be tailored to the different invasion severity classes. Forests in the high-severity class need a management program coordinated across different agencies and landowners to curb the increase of tallow populations to prevent stand replacing risks. The monitoring of Chinese tallow spread should focus on longleaf/slash pine, loblolly/shortleaf pine, and oak/gum/cypress groups, because the spread rate was higher in these forest-type groups. A better use of scarce resources could be to treat lands in the moderate- and low-severity classes to reduce the propagule pressure levels and post-invasion spread. For those counties with a minimal-severity condition, early detection and eradiction measures should be taken in a timely maner to prevent tallow from invading noninvaded neighboring counties. Managers may be able to treat a larger area of these lands for a given investment compared with lands already severely invaded.

Triadica sebifera (Chinese tallow tree).

Triadica sebifera is a valuable multipurpose agroforestry species in the central Himalayan region and across Asia, and is also a popular ornamental tree for its colourful autumn leaves. The fruit of T. sebifera contains two types of fat. The white, fleshy outer seedcoat (sarcotesta) produces a fat known as Chinese vegetable tallow, while the cotyledons of the seed (kernel) yield a drying oil called stillingia oil. These oils are used as a substitute for cocoa butter in the food industry, to make paints, varnishes, soaps and candles, and to waterproof umbrellas. The leaves contain a dye, used in Asia to dye silk black. As an agroforestry species, Triadica sebifera is a good soil binder and contributes to nutrient recycling. It is planted in tea plantations as a shade tree and is also a minor timber tree. Its wood is sometimes used to make various implements, toys, furniture and Chinese printing blocks. The root, bark and leaves are used in traditional medicine in China (PROSEA, 2018; PROTA, 2018).

A brief review of Triadica sebifera (Chinese tallowtree) in the southern United States, emphasizing pollinator impacts and classical biological control

Throughout history a great many plant species have been purposefully transported to new areas around the globe. Horticulture, the promise of new sources of plant material for industry, forage, food, and stabilization of soil are only a few of the motives for the early transcontinental exchange of plants. Many introductions have been beneficial or benign, however, some plants introduced into new areas are now considered invasive and detrimentally impact the environment. Chinese tallowtree [Triadica sebifera (L.) Small] (Euphorbiaceae) is an excellent example of the best intentions leading to unanticipated negative effects many decades later. Native to eastern Asia and now naturalized and widespread in many tropical, subtropical, and temperate areas in the world, Chinese tallowtree has proven to be one of the worst woody invasive plants. It is known for shading out native vegetation, capable of dominating areas following disturbance or even invading previously diverse undisturbed habitats. It is prevalent in the southern United States, especially along the Gulf Coast. Investigations into classical biological control of Chinese tallowtree have yielded at least two promising candidates but have raised objections among beekeepers and beekeeping organizations who prize the quality honey produced from an abundant spring nectar flow. In this review we discuss Chinese tallowtree’s invasive characteristics, detrimental effects, potential use as a biomass crop, and demonstrated or potential direct and indirect effects on native and non-native pollinators. We review the current state of identification and screening of biological control agents. Four research questions are presented which are designed to fill gaps in our knowledge of Chinese tallowtree and pollinators. We conclude that classical biological control efforts to reduce Chinese tallowtree populations are justified and, if successful, will likely improve habitat for native plants and native and exotic pollinators in restored areas.