Fungicides have been developed to protect plants against diseases and pests, which cause serious problems such as the loss of germination and vigour. The aim of this study was to test the germination and vigour of maize (Zea mays L.) seeds treated with several fungicides Apron® Star 42 WS (difenoconazole, thiamethoxam, and metalaxyl-m), Apron® XL (mefenoxam), Celest® XL (fludioxonil, mefenoxam) and thiram in the laboratory. In the greenhouse, the efficacy of fungicide treatment was evaluated in soil inoculated with Fusarium graminearum. The control consisted of untreated seeds. Germination and vigour were evaluated according to the International Seed Testing Association (1ST A) rules. The results from the standard gennination tests showed that all the fungicide treated seeds did not differ to the untreated control. The conductivity of solute leakage was read following slow and fast imbibition. Maize seeds treated with Apron® Star 42 WS, Celest® XL, Apron® XL and thiram improved or maintain vigour, which was indicated by a reduced or equivalent solute leakage following fast imbibition when compared with the untreated control. The good performance of fungicide treated seed expressed during conductivity test after fast imbibition correlated with the tetrazolium. All the fungicide treated seeds maintained the same viability as the untreated control following fast imbibition. After 6 h after fast imbibition, Apron® Star 42 WS, Celest® XL and Apron® XL treated seeds maintained similar germination percentages when compared to the untreated control with the exception of thiram treated seeds that exhibited a decline in seed viability. There was reduction in vigour in all the fungicide treated seeds fo llowing 24 and 40 h fast imbibition as illustrated by the reduction in germination percentage below the acceptable level (70%) when compared with the untreated control. The greenhouse study showed that all the fungicide treated seeds maintained the same emergence percentage in both inoculated and uninoculated soil with the exception of thiram treated seeds, where emergence improved in inoculated soil when compared to the untreated control. Apron® Star 42 WS and Celest® XL reduced the disease caused by F. graminearum in the inoculated soil. This study also revealed that the application of Apron® Star 42 WS, Celest® XL and thiram to seeds improved both the shoot and root dry mass of plants in the inoculated soil.
Dissertation (MInstAgrar)--University of Pretoria, 2011.