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Apple replant disease (ARD) is a common problem typifi ed by stunted growth and reduced yields in successive plantings of apple (Malus ×domestica Borkh.) in old orchard sites. ARD is attributed to biotic and abiotic factors; it is highly variable by sites, making it diffi cult to diagnose and overcome. In this experiment, we tested several methods of control- ling ARD in a site previously planted to apple for >80 years. Our objective was to evaluate practical methods for ARD management. We compared three different experimental factors: four preplant soil treatments (PPSTs) (compost amendments, fumigation with Telone C-17, compost plus fumigation, and untreated soil); two replanting positions (in the old tree rows vs. old grass lanes); and fi ve clonal rootstocks ('M.26', 'M.7', 'G.16', 'CG.6210', and 'G.30') during 4 years after replanting. The PPSTs had little effect on tree growth or yields during 4 years. Tree growth was affected by planting position, with trees planted in old grass lanes performing better than those in the old tree rows. Rootstocks were the most important fac- tor in overcoming ARD; trees on 'CG.6210' and 'CG.30' grew better and yielded more than those on other rootstocks. Rootstock selection and row repositioning were more benefi cial than soil fumigation or compost amendments in controlling ARD at this orchard. A disease complex or syndrome known as apple (Malus ×domestica Borkh.) replant dis- ease (ARD) has been reported in fruit growing regions worldwide for more than a century (Mai and Abawi, 1981). Replant disease becomes problematic as growers renovate old orchards and replace them with similar crop species. It is usually attributed not to unfavorable soil and root conditions per se, but to pathogens or other biotic factors in the root zone in conjunction with abiotic soil conditions (McKenry, 1999). The symptoms of ARD are diverse, and its causes are often complex and nonspecifi c (Mai et al., 1994). New orchards in affected sites do not establish well, and usually show diagnostic symptoms such as stunted growth above and below-ground, nutrient defi ciencies, drought stress, reduced yields and increased tree mortal- ity (Mai and Abawi, 1981; Mazzola, 1998). ARD may be less of a hindrance when growers can rotate crop species; but in many areas climate, economics, or other factors limit the fruit crops that can be grown, and replant problems become a serious threat to the tree-fruit industry. Replant problems impede efforts to replace obsolete or unproductive orchards with new fruit varieties and planting systems (Merwin et al., 2001). Biotic factors have been the focus of most ARD research, because soil fumigation or

Rootstock Selection, Preplant Soil Treatments, and Tree Planting Positions as Factors in Managing Apple Replant Disease