Submitted to: International Phytophthora Capsici Conference
Publication Type: Abstract Only
Publication Acceptance Date: 10/11/2011
Publication Date: 11/27/2007
Citation: Iriarte, F.B., Rosskopf, E.N., He, Z., Lin, Y. 2007. Inhibiton of Phytophthora capsici by a novel pesticide. International Phytophthora Capsici Conference. Interpretive Summary:
Technical Abstract: A potential new pesticide, referred to as ‘SPK’, is currently being investigated under a cooperative project between the University of Florida and the USDA, ARS. In vitro studies have been conducted on multiple plant pathogenic fungi and oomycetes. Preliminary laboratory studies were conducted using a simple media-amendment approach. A 0.7 cm diameter plug of a 4 - 6 day old culture of Phytophthora capsici was transferred to Petri plates containing 1/4 potato dextrose agar and a range of SPK concentrations from 0 to 1 %. Radial growth was measured after the 3rd, 6th, and 9th day of incubation at 26 oC under continuous light. Complete inhibition of growth of P. capsici occurred at concentrations of 0.4% SPK incorporated into culture medium. Consequently, an additional experiment was carried out, with SPK concentrations of 0, 0.1, 0.2, 0.3, 0.4 and 0.5 %. Three replications for each SPK concentration were included and the experiment was performed twice. Percent kill was calculated based on radial growth and IC50 values were calculated using probit analysis for toxicology. The average IC50 value for P. capsici was 0.15 %. In greenhouse trials, P. capsici-inoculated and non-inoculated soil was treated with 30 ml of 0, 2.5, 7.5, 10.0 and 12.5 % SPK solution. Pots were tarped and kept in the greenhouse for seven days. Tarps were removed and two-week-old peppers were transplanted into treated soil. Chlorosis in plants treated with the 12.5 % solution and stunting with all concentrations of SPK was observed. However, in inoculated plants, Phytophthora blight did not occur starting at a 10.0 % SPK concentration and surviving plants resumed normal growth. The experiment was repeated with four-week-old pepper transplants with similar results. Plant back studies are currently underway.