The effects of thyme oil and chlorine dioxide on the germination and production of conidia and mycelial growth of monilinia fructicola (G. winter) honey

Abstract

This study aims to research the in vitro effectiveness of thyme oil and chlorine dioxide (ClO2) on
mycelial growth, conidia production and conidia germination of Monilinia fructicola (G. Wint.)
Honey which causes brown rot in plums.While a 300 ppm dose of chlorine dioxide inhibits mycelial
growth by 77.2%, thyme oil at 30 ppm inhibits by 100%. The MIC value of chlorine dioxide is above
300 ppm. The ED50 values of thyme oil and chlorine dioxide have been determined as <3 and 15.3
ppm, respectively. While the spore germination of the pathogen is suppressed at high rates by 100
and 300 ppm chlorine dioxide (70 and 90%, respectively), the same doses of thyme oil suppress by 47
and 75%. Parallel to the effectiveness on germination the ED50 values of chlorine dioxide and thyme
oil are 18 and 112.2 ppm. The test chemicals affected the fruit yield of the fungus at varying rates.
Doses of 30, 100 and 300 ppm of chlorine dioxide affected the spore production at rates of 23.75,
37.5 and 43.75%. Doses of 3 and 10 ppm thyme oil affected the spore production by 77.7 and 96.5%
while doses 30 µl/ml and above inhibited fructification by 100%. The research results prove that
thyme oil, especially, and chlorine dioxide inhibit mycelial growth, spore germination and
fructification of M. fructicola by a significant amount, indicating that, after in vivo studies, both
chemical compounds may be used against monilia disease for plums after harvest.