Effect of Fungicide Spray Cover on Botrytis Cinerea Infection in Grape Bunches

  • J.C. Brink Department of Plant Pathology, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa
  • G. Holz Department of Plant Pathology, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa
  • P.H. Fourie Department of Plant Pathology, Stellenbosch University, Private Bag X1, 7602 Matieland (Stellenbosch), South Africa

Abstract

The effect of fungicide spray cover on Botrytis cinerea infection in grape bunches was determined. Bunches were sprayed at pea size and bunch closure with different volumes of a mixture of fenhexamid and a yellow fluorescent pigment, and the percentage fluorescent pigment coverage on pedicels was determined. Bunches were subsequently dusted with dry airborne conidia of B. cinerea in a settling tower and incubated for 24 h at high relative humidity (98%). Infection was determined by estimating the amount of B. cinerea infections on susceptible bunch parts (pedicel, receptacle and rachis) with isolations onto paraquat (herbicide) and Kerssies (B. cinerea selective) mediums.  Linear regressions for the part × stage combinations of percentage B. cinerea incidence on different bunch
parts were fitted on mean coverage levels. An increase in spray cover caused linear reductions in levels of B. cinerea on bunch parts. Higher B. cinerea incidences were recorded at pea size. Furthermore, higher B. cinerea incidences were found on paraquat medium for both stages, than on Kerssies medium. The information gathered from this study will be used to facilitate future determination of minimum effective coverage levels for effective B. cinerea control in grape bunches.
Published
2017-03-01
Section
Articles