'Copper and Bronze in Art' and the Search for Rare Corrosion Products

Information taken from David A. Scott’s book “Copper and Bronze in Art” was crucial for research on copper corrosion products in Stuttgart. Examples discussed are the nature and variability of ‘Black Spots’ (aka ‘Brown Fuzzies’); cupric hydroxide by cleaning, patination, and pigment synthesis; the wondrous phenomenon of curly malachite; chalconatronite formed by contact to soda glass; the formation of copper formates by glass-induced metal corrosion; and synthesis and X-ray diffraction of basic copper acetates (‘verdigris’).

Recovery of Copper and Cyanide from Copper-cyanide Solution by Direct Electrolysis

Using direct electrolysis method, the recovery of copper and cyanide from high concentration copper cyanide solution was researched. The distribution of copper cyanide species was calculated by stability constants and balance equation. The results showed that the cupric ion was confirmed to generate at low potential (<0.4V) on the titanium electrode coated with iridium and tantalum oxides during the electrolysis process, which led to the oxidation of cyanide and the precipitate obtained on the anode was proved to be cupric hydroxide by XRD at high potential. The copper was recovered by direct electrowinning, the recovery of copper increased with increasing temperature, which reached 80% at 70°C; but the loss of cyanide was serious, the free cyanide concentration was significantly lower than original value.

Foliar chemical protection against Pantoea ananatis in onion is negated by thrips feeding

Center rot of onion, caused by Pantoea ananatis, is an economically important disease in onion production in Georgia and elsewhere in the United States. Growers rely on frequent foliar applications of bactericides, and in some cases, plant defense inducers to manage this disease. However, regular prophylactic applications of these chemicals is not cost-effective and may not be environmentally friendly. Thrips (Thrips tabaci and Frankliniella fusca) are vectors of P. ananatis, and their feeding may compromise the effectiveness of foliar applications against P. ananatis. In this study, foliar treatments of acibenzolar-S-methyl (Actigard 50WG), cupric hydroxide (Kocide 3000), and Actigard + Kocide were evaluated for their effectiveness in the presence and absence of thrips infestation at two critical onion-growth stages; bulb initiation and bulb swelling. Onion growth stage had no impact on effectiveness of either Kocide or Actigard. In the absence of thrips, Kocide application resulted in reduced center rot incidence compared with Actigard, regardless of the growth stage. However, when thrips were present, the efficacy of both Kocide and Actigard was reduced with bulb incidence not significantly different from the non-treated control. In independent greenhouse studies in the presence or absence of thrips, it was observed that use of protective chemicals (Kocide or Actigard and their combinations) at different rates also affected the pathogen progression into the internal neck tissue and incidence of bulb rot. These results suggest that thrips infestation can reduce the efficacy of protective chemical treatments against P. ananatis.

Fabrication of Superhydrophobic Coatings on Copper Substrate

Cupric hydroxide films with new hierarchical architecture were directly fabricated on copper substrate via a solution-immersion process at a constant temperature of 23°C. Stable superhydrophobic Cu(OH)2 surface was obtained after Cu(OH)2 films were modified with hydrolyzed 1H, 1H, 2H, 2H-Perfluorooctyltrichlorosilane (C8H4Cl3F13Si, FOTMS). In addition, the growth mechanism of the cupric hydroxide films was further discussed.

Management of Transplant House Spread of Acidovorax avenae subsp. citrulli on Cucurbits with Bactericidal Chemicals in Irrigation Water

Bacterial fruit blotch (BFB), caused by Acidovorax avenae subsp. citrulli, is a seed-borne disease of cucurbits that spreads rapidly in the warm, humid environment of the transplant house, often resulting in high numbers of infected plants going into the field. The only control options for BFB once it gets into a transplant house are crop destruction or multiple applications of a copper-containing bactericide/fungicide. In this study, various treatments were compared with the standard foliar spray application of cupric hydroxide for BFB control under transplant house conditions. Peroxyacetic acid at 80 μg/ml and ionized copper at 1.0 and 1.5 μg/ml applied through the daily irrigation water were more effective than cupric hydroxide in reducing spread of A. avenae subsp. citrulli. Combining ionized copper or peroxyacetic acid in the irrigation water with a weekly foliar application of acibenzolar-S-methyl was most effective in reducing spread. The utilization of these transplant house treatments along with the elimination of all transplants with symptoms or near plants with symptoms should greatly reduce the chances of introducing BFB into fields on transplants. Accepted for publication 14 November 2008. Published 29 January 2009.

Efficacy of Organically Acceptable Fungicides for Management of Early and Late Leaf Spot Diseases on Partially Resistant Peanut Cultivars

Field experiments were carried out in Georgia and North Carolina to evaluate the efficacy of fungicides approved for the organic management of early leaf spot, caused by Cercospora arachidicola, and late leaf spot, caused by Cercosporidium personatum, in peanut (Arachis hypogaea) fields planted to cultivars with partial resistance to one or both pathogens. Copper treatments alone or in mixtures resulted in less disease than a non-treated control. In Georgia, sulfur provided some disease suppression, but not as much as treatments with copper sulfate. Neem oil did not affect disease severity. Mean pod yields across years were significantly greater than the non-treated control only for copper sulfate in Georgia and cupric hydroxide in North Carolina. The minimal yield response to treatments suggests that under similar situations, the frequency of copper-based fungicide applications may be reduced with little affect on yield. Accepted for publication 16 January 2008. Published 17 March 2008.

Effects of Timing of Copper Sprays, Defoliation, Rainfall, and Inoculum Concentration on Incidence of Olive Knot Disease

The olive knot pathogen, Pseudomonas savastanoi, causes galls on shoots, branches, fruit, and leaves. Shoots girdled by galls die. Any fresh wound is susceptible to infection, but the most common entry sites are leaf scars. Leaf scars are most susceptible to infection during the first 2 days after leaf fall and remain susceptible for 7 more days. Simulated leaf scars on ‘Manzanillo’ olive trees were created by removing leaves from healthy shoots at approximately monthly intervals from December through June 1997-98, 1998-99, and 1999-2000. Trees were treated with a water suspension of cupric hydroxide (Kocide DF40) at 3 g/liter one, two, or three times in 1998-99 and 1999-2000 with a hand-gun sprayer. Generally, disease control improved with more applications (P = 0.008 and 0.032 in 1999 and 2000, respectively). Disease incidence was greatest on shoots that were defoliated in March 1998, April and June 1999, and March and May 2000. Cumulative rainfall 2 and 9 days after each defoliation was recorded. Disease incidence was positively correlated (P = 0.031 and 0.023 for 2 and 9 days, respectively) with spring (March through June) but not winter (December through February) rainfall. Comparable simulated leaf scars were inoculated in December and April 1997-98 and 1998-99 with 104, 106, and 108 CFU/ml of the pathogen and treated with a water suspension of cupric hydroxide at 3 g/liter using a handheld pump sprayer. Inoculated and noninoculated, nontreated shoots were included. More disease developed in April than in December inoculations (P = <0.0001) in both years. Disease incidence increased with increasing inoculum concentration (P = <0.0001) in both years and was lower in shoots treated with Kocide DF40 (P = <0.0001). Our work demonstrated that the common grower practice of one post-harvest application of copper bactericide provides only minimal protection against olive knot, and that additional sprays in spring are needed to substantially improve disease control.

Incident Irradiance and Cupric Hydroxide Container Treatment Effects on Early Growth and Development of Container-grown Pawpaw Seedlings

The North American pawpaw [Asimina triloba (L.) Dunal] has great potential as a fruit crop or as a landscape plant. The influence of incident irradiance on pawpaw seedling growth and development in containers was examined in the greenhouse and outdoors. Root spiraling can be a problem for container-grown pawpaw seedlings; therefore, the influence of paint containing cupric hydroxide [Cu(OH)2] at 100 g·L-1 applied to the interior of containers on plant growth was also examined in a greenhouse environment. In pawpaw seedlings grown outdoors for 11 weeks, low to moderate shading levels of 28%, 51%, or 81% increased leaf number, total leaf area, and total plant dry weight (DW) compared to nonshaded seedlings. A shading level of 81% decreased the root to shoot ratio by half compared to nonshaded plants. Shading of 98% reduced leaf number, leaf size, and shoot, root, and total plant DW. Shading increased leaf chlorophyll a and b concentrations for pawpaw seedlings grown outdoors, while it decreased average specific leaf DW (mg·cm-2). In a separate greenhouse experiment, pawpaw seedlings subjected to shade treatments of 0%, 33%, 56%, 81%, or 98% did not respond as greatly to shading as plants grown outdoors. Greenhouse-grown plants had greater total and average leaf area under 33% or 56% shading than nonshaded plants; however, shading >56% reduced root, shoot, and total plant DW. Total shoot DW was greater in greenhouse grown plants with 33% shading compared to nonshaded plants. Pawpaw seedlings in control and most shade treatments (33% to 81%) in the greenhouse environment had more leaves and greater leaf area, as well as larger shoot, root, and total plant DW than seedlings in similar treatments grown outdoors. The greenhouse environment had a 10% lower irradiance, a 60% lower ultraviolet irradiance, and a significantly higher (1.23 vs. 1.20) red to far-red light ratio than the outdoors environment. Treatment of container interiors with Cu(OH)2 decreased total and lateral root DW in nonshaded seedlings, and it adversely affected plant quality by causing a yellowing of leaves and reduction of chlorophyll levels by the end of the experiment in shaded plants. Growth characteristics of pawpaw seedlings were positively influenced by low to moderate shading (28% or 51%) outdoors and low shading (33%) in the greenhouse. Seedlings did not benefit from application of Cu(OH)2 to containers at the concentration used in this study. Commercial nurseries can further improve production of pawpaw seedlings using low to moderate shading outdoors.