Cultural Practices and Chemical Treatments Affect Phytophthora Root Rot Severity of Blueberries Grown in South Mississippi

Abstract

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 than normal root system. Infected plants generally have fewer and poorer quality fruit than noninfected plants. Two 5-year studies were initiated in south Mississippi to evaluate the effect of drainage and fungicide treatments on Phytophthora root rot severity of mature, infected rabbiteye blueberries and the effect of drainage, bed height, and fungicide treatments on disease severity of young rabbiteye and southern highbush blueberries planted into Phytophthora infested soil. In the first study using mature ‘Tifblue’ plants, significant improvements in plants were due to the subsoil treatment and to twice-a-year treatments with the fungicide metalaxyl. In the second study of young ‘Tifblue’ and ‘Misty’ plants grown in a Phytophthora infested soil, there were no significant main effects due to bed height, drainage, or fungicide treatment in the height, size, or percentage of living plants with either cultivar; however, there was a significant interaction between bed height and fungicide treatment. After 4 years, young ‘Tifblue’ plants grown in infested soil on raised beds treated with metalaxyl were taller and had a greater percentage of living plants than those grown on untreated flat beds.