Survival of Southern Highbush Blueberry Cultivars in Phytophthora Root Rot-Infested Fields in South Mississippi

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 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 transplanted into fields infested with the root rot pathogen, Phytophthora 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 those grown in soils amended with peat moss were more vigorous than those grown in soils with no amendment. In the 2008 study, plants grown in soil amended with pine bark were more vigorous than those grown in soil amended with peat moss. However, plant vigor declined each year, and most plants died within 3 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.