Abstract
A 10-fold-diluted suspension of a fertilizer paste (product name: TP, Taki Chemical, Hyogo) was tested for suppression of violet root rot of apple, caused by Helicobasidium mompa in infested kuroboku soil (soil texture: L). In pot experiments with infested soil, disease severity on apple seedlings or rootstocks (Malus prunifolia var. ringo) treated with TP was lower than on those treated with tap water. While TP did not eradicate the pathogen colonizing bark tissues of apple, mycelial growth in the soil treated with TP was suppressed for 60 d. Mycelial growth was also suppressed 10 cm below the soil surface after 41 d of irrigation with 10 mm water at 5- or 10-d intervals. In a field trial in heavily infested soil, disease severity of apple trees with TP was equivalent to that treated with the fungicide fluazinam and slightly lower than that of the control. With TP in the field, mycelia were infrequently observed even on the root surface of damaged trees. These results suggest that the soil with the fertilizer paste applied on the soil surface can suppress disease development, by suppressing mycelial growth.
