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- Author or Editor: Eldon I. Zehr x
`Redhaven' peach trees were planted on a nonfumigated peach tree short life (PTSL) site in Pontiac, S.C. The experimental design was a split plot with 12 replicates. Preplant subplot treatments were 0, 3, and 6 kg of hydrated lime mixed with 1.9 cubic meters of native soil (Lakeland sand) per planting hole. Main plot treatments consisted of mixing in the planting holes 0 or 5 liters of soil taken from a nearby orchard site that had shown “suppressive” tendencies towards ring nematode reproduction. Hydrated lime treatments increased soil pH by 0.6 to 1.4 units. Boron deficiency occurred in the 6-kg plots. Hydrated lime did not significantly reduce PTSL as 88%, 79%, and 92% of the trees in the 0-, 3-, and 6-kg plots, respectively, died from PTSL by the fifth year. No differences in survival were found between the nonsuppressive and suppressive soil treatments, as both had 86% tree death from PTSL. No trends in ring nematode populations were found among treatments.
Peach tree short life (PTSL) is a serious peach tree disease syndrome on replant orchard sites in the Southeast. Pseudomonas syringae pv. syringae is a bacterial disease often associated with tree injury and death on these PTSL sites. Rootstocks that have better tolerance to ring nematodes such as Lovell have less PTSL death. Tissue-cultured peach embryos and/or explants have shown increased resistance to Pseudomonas syringae and Xanthomonas campestris pv. pruni, another bacterial peach pathogen, in laboratory and greenhouse screenings. Tissue-cultured `Redhaven' (RH), `Redskin' (RS), and `Sunhigh' (SH) peach cultivars on their own roots were planted with SH seedlings and RH and RS budded to Lovell rootstock on a severe PTSL site in South Carolina. Treatments beside cultivar/rootstock combination included preplant fumigation vs. nonfumigation. PTSL appeared in the third year and by year 4 significant tree death occurred. Tissue-cultured RH, RS, and SH trees had 54%, 55%, and 88% PTSL death, respectively, compared to RH (17%) and RS (29%) on Lovell or the SH seedlings (25%). Fumigation significantly decreased PTSL in both RS combinations but not RH. These data suggest that the tolerance of the cultivar root system to PTSL-inducing factors such as ring nematodes was more important in PTSL than scion resistance to bacteria.
During the 1984 growing season, 156 peach and 40 nectarine cultivars, 49 plant introductions, and 33 Prunus species or species hybrids were evaluated for susceptibility to bacterial spot [Xanthomonas campestris pv. pruni (Smith 1903) Dye 1978] in North Carolina and South Carolina. Fruit and leaf infection and percentage of defoliation were evaluated in North Carolina, while only leaf infection data were evaluated in South Carolina. No cultivar was immune, but susceptibility varied greatly. Based on leaf infection in the 2 locations, it was concluded that disease pressure was greater in North Carolina. Correlation of fruit infection severity with leaf infection severity and percentage of defoliation in North Carolina was r = 0.30 (P = 0.01) and r = 0.54 (P < 0.01), respectively. Correlation between leaf infection severity and percent defoliation was r = 0.51 (P < 0.01) and r = 0.00 (NS) in North and South Carolina, respectively.