Abbreviation: PTSL, peach tree short life. Research Nematologist. 1 Research Horticulturist. We thank Bruce Topp, Granite Belt Horticultural Research Station, Queensland, Australia, for his suggestions and comments during the preparation of this
T.G. Beckman, W.R. Okie, and A.P. Nyczepir
Andrew P. Nyczepir and Bruce W. Wood
). Two common causes of early tree death are a disease complex known as PTSL and Armillaria root rot ( Miller, 1994 ). Peach tree short life is reportedly caused by a predisposition of trees to bacterial canker ( Pseudomonas syringae pv. syringae van
W.R. Okie, T. G. Beckman, and A.P. Nyczepir
Lovell rootstock is recommended for Peach Tree Short Life (PTSL) sites in the Southeast because it outlives Nemaguard. No genetic studies of PTSL tolerance have been done. Clonally replicated peach seedlings [Prunus persica (L.) Batsch] of Lovell, Nemaguard and four F1 selections of Lovell × Nemared were tested for field survival in a high density planting on a PTSL site. Rootstock families (12 seedlings × 8 ramets each) differed in growth, survival and longevity. Genetic variation was comparable to environmental variation for most families. Based on seedling within rootstock family, estimated broad-sense heritabilities for survival and longevity were high. The use of clonally replicated seedlings allowed the selection of apparently superior individuals from both Lovell and the other more short-lived rootstock families in a single screening after 6 years. Survival of Lovell at that time was 50% compared to 16-29% for other families. Across all families, all 8 ramets were dead for 21 seedlings, whereas all 8 were alive for only 3 seedlings.
Gregory L. Reighard and Eldon I. Zehr
`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.
Dennis Werner, Michael L. Parker, and Elisabeth Wheeler
Peach tree short life (PTSL), a major disease complex impacting peach culture in the southeastern United States for decades, accounts for millions of dollars of losses annually. In spite of the overwhelming amount of research that has been conducted on PTSL, many uncertainties still exist regarding the factors involved in the syndrome and the true cause of tree death. As a consequence, we examined the wood structure and anatomy of 6-year-old peach trees, some showing the initial visible symptoms of PTSL, and others that appeared unaffected and healthy. Very dramatic differences in wood anatomy were observed between healthy and stricken trees. Stricken trees showed a total lack of vessel formation in some earlywood zones, a decrease in vessel formation in latewood, and a marked increase in ray parenchyma cells. Healthy trees showed normal vessel and ray formation. Preliminary results indicate that in some way PTSL may be associated with increased gum production in the xylem and decreased earlywood vessel production, thereby significantly reducing water conduction, leading to tree death. Results of studies currently in progress to further investigate this hypothesis will also be presented.
Michael L. Parker, Dave Ritchie, and Andy Nyczepir
A study was initiated in 1994 to evaluate the performance of the recently released peach rootstock Guardian TM (BY-5209-9), compared to Lovell, the commercial standard in North Carolina. `Redhaven' was the scion for both rootstocks. Guardian&™ is reported to be tolerant to root-knot nematodes and not affected by ring nematodes, which contribute to the incidence of peach tree short life (PTSL). The site of this study has a history of poor peach tree survival. Six-year-old trees were removed because of tree mortality from PTSL in Spring 1993. After tree removal, one-half of each existing row was pre-plant fumigated and trees were replanted over the rows of the previous orchard in Feb. 1994. In Spring 1996, tree mortality for the trees planted on Lovell was 30%, compared to 10% for the trees planted on GuardianTM. Trunk cross-sectional area for trees grown in the fumigated soil was approximately double that of trees grown in the unfumigated soil for both GuardianTM and Lovell. The 1996 fruit crop was eliminated from frost/freeze conditions and 1997 yields will be discussed. In Fall 1996, one-half of the trees were treated with a post-plant nematicide to determine if such treatments are necessary or beneficial with the GuardianTM rootstock.
T.G. Beckman, G.L. Reighard, A.P. Nyczepir, and W.R. Okie
Thirteen rootstocks grafted with Redhaven peach were established on a severe peach tree short-life (PTSL) site in central Georgia. Most rootstocks tested were peach seedling types: Lovell, Nemaguard, Guardian (BY520-9), BY520-8, Boone County, Bailey and two `Tennessee Natural' selections. A seedling plum rootstock, St. Julian, was also used. Clonal type rootstocks included a peach × almond hybrid, GF677; plum, GF43 and Damas 1869; and a plum hybrid, GF655-2. Trees on Guardian displayed the best survival with only 20% mortality due to PTSL, through 7 years. In contrast, 40% of trees on Lovell succumbed to PTSL. Currently, Lovell is the recommended rootstock for PTSL-prone sites. Other rootstocks ranged from 50% to 100% mortality due to PTSL. Trees on Guardian displayed significantly higher vigor through the first 4 years following planting compared to trees on Lovell. Furthermore, trees on Guardian produced significantly greater yields than those on Lovell, in all but 1 year. Rootstock effects on tree survival, vigor, bloom and harvest dates, fruit yield and size, and suckering will be discussed.
A.P. Nyczepir and W.R. Okie
Gregory L. Reighard, William A. Watson, D.C. Coston, and John D. Ridley
Thomas G. Beckman, Philip A. Rollins, James Pitts, Dario J. Chavez, and Jose X. Chaparro
rooted trees of ‘Majestic’ that was observed in this trial is not surprising. Table 1. Rootstock influence on cumulative mortality due to Armillaria (ARR), peach tree short life (PTSL), and other causes on a severe Armillaria-infested grower site in