Rubber dandelion (Taraxacum kok-saghyz, Rodin) is being developed as a temperate-zone source of rubber, but best agronomic practices must be determined before it can become a viable supplement to imported rubber produced from para rubber tree (Hevea brasiliensis, hevea) plantations located mostly in Southeast Asia. In our study, the effect of planting density and harvest time on yield was determined by transplanting 1.5-month-old greenhouse-produced plants at planting densities of 1.24, 2.47, 4.94, and 9.88 million plants/ha, randomized across four planting boxes with two densities per box (i.e., two planting areas at each density). Half of each planting area was selected randomly and hand-harvested after 6 months, and the remaining plants were hand-harvested after 1 year. Rubber yields per plant were greater after 1 year than after 6 months, but yields per unit area were similar as a result of the loss of half the plants during the severe 2013–14 Ohio winter. A maximum rubber yield of 960 kg dry rubber/ha was obtained from the 9.88 million-plants/ha planting density after 1 year, but root size was significantly decreased compared with lower densities, and appeared too small for mechanical harvest. A planting density between 2.47 and 4.94 million plants/ha may produce the optimal combination of root size and total rubber yield. Greater rubber concentrations, faster-growing plants, short-season germplasm, and in-field weed control are required before yields obtained in outdoor planting boxes can be matched or exceeded on farms, especially in a direct-seeded rubber dandelion crop.

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Background: Over 8% of the US population have detectable Type I Hevea latex IgE antibodies and, upon exposure to natural latex and rubber products, are at risk for potentially dangerous reactions, especially in dental settings where these products are exposed to mucosal membranes. Methods: Extractable antigenic protein levels were quantified in dental dams, examination gloves, and various other dental and rubber products. ASTM standards D6499 (antigenic protein) and D5712 (total protein) were used to quantify the protein content. Results: In dental dams, extractable protein content ranged from <3 to 130-200 μg/dm 2 , which are generally accepted by regulatory bodies to be low/nonsensitizing levels and high/potentially sensitizing levels, respectively. In addition, although examination gloves from Malaysian glove manufacturers consistently exhibited a lower extractable protein content (<9 μg/dm 2) than gloves from Thai manufacturers (16-23 μg/dm 2), these levels are both below the 50 μg protein/g latex film threshold accepted by FDA and used by manufactures. There was no correlation between extractable protein content and the price or thickness of dental dams or examination gloves. Most of the other assorted dental products tested displayed low extractable protein content (<2.5 μg/dm 2). Nearly all dental products made from natural rubber contained detectable antigenic Hevea proteins, subjecting previously sensitized patients and providers to risk of severe allergic reaction. A case study describes a female patient, with no previous history of Type I latex allergy, reacted severely to a dental dam mouth exposure, necessitating her admission to the intensive care unit (ICU) of a local hospital for management of respiratory failure, with discharge after 4 days. Conclusions: It is clear that some dental products may pose a significant risk of Type I latex protein allergy sensitization, due to repeated contact, and that a single exposure can induce a severe reaction in a previously sensitized person, even when no prior latex allergy history is known.

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