New fungicides for the management of pythium root rot in floatbed seedling production system

Abstract

Pythium root rot possess major threats on float bed seedling productions. It is caused by oomycetes in the Pythium genus. It causes a huge of loss money as well as the seedlings. It is critically important to control this disease before it causes economic losses. A study was carried out from September 2013 to November 2013 at Kutsaga Research Station in the greenhouse. The purpose of the study was to evaluate the efficacy of metalaxyl + mancozeb from a new source (Citchem) for the control of Pythium root rot in the float bed seedling production system as well as to establish effective rates. Pythium is destructive plant pathogen that causes the damping off and root rot of seedlings in hydroponic seedling production. Two fungicides were used and these were Ridomil MZ 68% WG (metalaxyl) and metalaxyl + mancozeb (Metalaxyl-Citchem). Ridomil (metalaxyl) was used as the standard fungicide at a concentration of 05 parts per million per litre of water (ppm/L) (0.125 g/L of water). Metalaxyl + mancozeb was applied as two concentrations, 05 ppm/L (0.0625 g/L of water) and 10 ppm/L (0.125 g/L of water). One tobacco variety (KR K26) was used for seedling production, and the fungicides were applied at six weeks after seeding. Pythiummyriotylum was the test pathogen and was inoculated a week after fungicides had been applied. The tobacco seedlings were assessed for Pythium root damage at 9 and 22 days after inoculation (DAI). The assessments were done using a Pythiumdamage score (0-5) and the results were recorded on data sheets. The results revealed that all fungicides tested were effective, and were fungistatic against the test pathogen P. myriotylum. At 9 DAI Ridomil (metalaxyl) was the most effective and recorded an overall mean of 0.8 on the Pythium damage score. Metalaxyl + mancozeb (10 ppm/L) was found most effective at 22 DAI and recorded an overall mean of 1.9 on the Pythium damage score. In both assessments, the results showed that root damage varied among treatments (p<0.05). In both assessments the untreated seedlings were severely damaged by Pythium root rot.