Submitted to: International Journal of Fruit Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2011
Publication Date: 3/15/2012
Citation: Smith, B.J. 2012. Survival of southern highbush blueberry cultivars in Phytophthora Root Rot Infested fields in South Mississippi. International Journal of Fruit Science. 12:146–155. DOI: 10.1080/15538362.2011.619361.
Interpretive Summary: Phytophthora root rot is a serious disease of blueberries especially those grown on poorly drained soils. Four studies were conducted to determine the relative susceptibility of 19 southern highbush blueberry cultivars to root rot and to determine the effect of two cultural practices on the establishment of these cultivars in soils infested with the root rot pathogen. Most plants of each cultivar tested died within four years of transplanting, and the root rot pathogen was isolated from the roots of most of the plants that died. Neither cultural practice evaluated (raised beds and organic soil amendments) increased the survival percentage or vigor rating of any of the southern highbush blueberry cultivars. This information will be used by blueberry growers, extension specialists and research scientists making planting recommendations for blueberries in areas where root rot is known to occur.
Technical Abstract: Phytophthora root rot is an important disease of commercial blueberries and is most severe when blueberries are grown in wet soils with poor drainage. Symptoms of Phytophthora root rot include small, yellow or red leaves, lack of new growth, root necrosis, and a smaller root system than healthy plants. Four studies were conducted in south Mississippi to evaluate the effect of bed height and soil amendment on the survival of 19 southern highbush blueberry cultivars grown in fields infested with the root rot pathogen, Phytophthora cinnamomi. One-year-old plants were transplanted into a field whose soil was known to be infested with P. cinnamomi. Plants were rated twice a year for overall vigor on a scale of 0 = plant dead to 5 = most vigorous. The most vigorous cultivars were: Southmoon in the 2005 study, Gulfcoast in the 2006 study, and Springhigh in the 2008 study. In the 2005 and 2006 studies, plants grown on raised beds were more vigorous than those grown on flat beds and plants grown in soils amended with the peat moss were more vigorous than those grown in soils with no amendment. However, in the 2008 study plants grown in soil amended with pine bark were more vigorous than those grown in soil amended with peat moss. Each year in each study plant vigor declined, and most plants died within three years of planting whether they were planted on raised or flat beds and whether they received any soil amendments or not. No cultivar thrived in any planting. These studies demonstrate that southern highbush blueberries should not be planted in soils known to be infested with P. cinnamomi.