New York State Flower Industries , Inc
Fusarium stem rot is caused by the fungus, Fusarium roseum, and is a distinct disease from Fusarium wilt cause by F. oxysporum f. sp. dianthi. Fusarium oxysporum f. sp. dianthi enters the plant through the root tips and grows throughout the water-conducting tissue of the plant while F. roseum usually attacks theouter portion of the stem. In the past, F. roseum has been considered main ly to cause a basal cutting rot and a stem rot on young plants causing the most damage to cuttings during propagation and to young rooted cuttings when they are benched. In the past few years, carnation growers in the north eastern USA have experienced moderate to severe losses from the Fusariumstemrot disease. However, these losses were not from stem rot on young rooted cuttings, but resulted from damage on mature flowering plants. A pro gram was initiated to study this disease in 1970. The study was supported in part by a grant from the Pennsylvania Flower Growers (Dillon Research Fund) and the field work was done in cooperation with Mr. Herman Hellberg of the Peter Hellberg Company, Chalfont, Pa. Damage occurs on mature flowering plants as a dieback of the stubs left when flowers are cut or plants are pinched (Fig. 1, 2). The fungus grows down the stub killing it (Fig. 2a, 3a), and then into the side break (Fig. 2b, 3c) or main stem (Fig 2c, 3b) and may girdle the stem causing wilting and death of the branches and reducing the productivity of the plant (Fig. 3). When the relative humidity in the greenhouse is high for a period of time, the fungus can be seen growing on infected stubs (Fig. 5, 6). Often a stem is girdled by the fungus about the time a flower is ready to be cut resulting in the loss of that flower just prior to harvest (Fig. 4). These symptoms are called the stub dieback phase of Fusarium stem rot of carnation and are caused by the fungus, F. roseum 'Graminearum'.
Keywords: Disease Stem Rot F. roseum 'Graminearum'. fungus sidebreaks