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William C. Kreuser and Frank S. Rossi

( Aynardi et al., 2011 ; Aynardi and Uddin, 2013a , 2013b ; McCall and Focht, 2010 ; Popko et al., 2010 ; Popko and Jung, 2013 ). Acute and chronic phytotoxicity is a known limitation of PDSOs ( Hodgkinson et al., 2002 ). Acute phytotoxicity results

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Ed Stover, Youjian Lin, Xiaoe Yang, and Tripti Vashisth

study were to assess phytotoxicity at a range of cyanamide concentrations and determine the potential benefit of using cyanamide to hasten flowering and reduce bloom duration of citrus in south Florida. This work was discontinued due to a change in

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David Bubenheim, Kanapathipillai Wignarajah, Wade Berry, and Theodore Wydeven

Recycling wastewater containing soaps and detergents for plant growth is highly desirable when fresh water is limited. This is especially true during times of drought and is imperative in some specialized situations such as a regenerative space habitat. To regenerate food, water, and air, the National Aeronautics and Space Administration's Controlled Ecological Life Support System (CELSS) must recycle wastewater commonly known as gray water. The anionic surfactant Igepon is the principal ingredient of many detergent formulations and soaps and is a prime candidate for use in a space habitat. To determine if gray water would have phytotoxic effects on crops grown in a CELSS, `Waldmann's Green' lettuce (Lactuca sativa L.) was grown in nutrient solutions containing varying concentrations of Igepon TC-42. Igepon concentrations of 250 mg·L-1 or higher in nutrient solutions resulted in phytotoxic effects in lettuce. Thus, the toxic threshold of Igepon is <250 mg·L-1. Toxicity symptoms include browning of the roots within 4 hours of exposure to Igepon followed by suppression of root dry mass within 24 hours. Plant death never resulted from exposure to Igepon used in these experiments, although roots were killed. The phytotoxic effect of Igepon was not persistent; plants initially displaying acute toxicity show clear signs of recovery within 3 days of initial exposure. Further, when fresh plants were exposed to these same nutrient solutions 3 days or more following initial Igepon addition, no phytotoxic effect was observed. The elimination of the phytotoxicity was associated with a decrease in fatty acid components in the nutrient solution associated with Igepon. The degradation of phytotoxicity appears to be associated with microbes present on the surface of the roots and not directly due to any plant process or instability of the surfactant.

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Sridhar Polavarapu

A common practice in highbush blueberry (Vaccinium corymbosum L.) culture is to use combinations of insecticides and fungicides to reduce the number and cost of pesticide applications. In response to apparent phytotoxicity observed in commercial fields that were treated with combinations of diazinon and captan formulations, phytotoxicity of two formulations of diazinon (Diazinon AG600 and Diazinon 50W) and captan (Captan 80WP and Captec 4L) was investigated on highbush blueberries during 1997 and 1998. Phytotoxicity injury similar to injury observed in commercial fields was reproduced in treatments with diazinon and captan mixtures in all experiments. The Diazinon AG600 and Captec 4L mixture was the most severe and caused significantly more phytotoxic-ity to fruit and leaves than individual treatments of Diazinon AG600, Captec 4L or untreated control. Separation of diazinon and captan applications by 8 h significantly reduced phytotoxicity compared to mixture treatments. Injured fruit and leaves recovered over time and most treatments showed only a mild injury at the time of harvest. Phytotoxicity on fruit and leaves caused by Diazinon AG600 and Captec 4L mixture was significantly affected by application date with the earliest application causing the greatest injury. These data indicate that diazinon and captan mixtures cause phytotoxicity on highbush blueberries and therefore the two should not be applied in combination.

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Fredric Miller and Susan Uetz

Horticultural oil and insecticidal soap were as effective as conventional insecticides and miticides in controlling a variety of sap-feeding insects and mites on common greenhouse crops. Neem extract (Margosan-O or Azatin) was less consistent and provided intermediate to good control of a variety of sap-feeding insects and mites on common greenhouse crops. Except for purple heart (Setcreasea purpurea K. Schum. & Sydow) and wax ivy (Hoya carnosa R. Br.), repetitive sprays of horticultural oil, insecticidal soap, and neem extract (Azatin) did not seem to cause any noticeable phytotoxicity or effect the growth of 52 species or cultivars of bedding plants and 13 species of foliage plants examined in this study. Repetitive sprays of horticultural oil and insecticidal soap significantly affected plant height and final quality of some poinsettia cultivars evaluated in this study.

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Christian Nansen, Rachel Purington, and Machiko Murdock

of ornamental crop plants. “Phytotoxicity” is defined as the temporary or long-lasting effects of a compound (e.g., a pesticide) on plants ( European and Mediterranean Plant Protection Organization, 2014 ). Above levels causing plant stress, reduction

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John E. Kaminski, Tim T. Lulis, and Travis R. Russell

the turfgrass. Most conventional hydraulic fluids are phytotoxic to turfgrass and, if the leak is not detected and turf not immediately remediated, can create extensive turfgrass necrosis ( Johns and Beard, 1979 ). Conventionally, hydraulic fluids are

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Thomas Graham, Ping Zhang, Youbin Zheng, and Michael A. Dixon

many of the harmful chemical residues associated with other treatment technologies (e.g., chlorination). These properties make the technology attractive to horticultural production; however, data are lacking on the phytotoxicity of aqueous ozone

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Thomas E. Marler and Nirmala Dongol

( Fig. 1C ). These barren sites had received no pesticide applications, so observations indicated a phytotoxic chemical legacy may be causal. However, no effort has been made to understand this phenomenon. If scale-infested cycad litter is validated as a

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Susan L.F. Meyer, Dilip K. Lakshman, Inga A. Zasada, Bryan T. Vinyard, and David J. Chitwood

nematicide, it was also important to determine whether it was harmful to seedlings of vegetable crops. Clove oil, and its primary constituent eugenol, have been reported to have phytotoxic effects ( Bainard et al., 2006 ; Boyd and Brennan, 2006 ; Boyd et al