Physical, cultural, and chemical alternatives for integrated management of charcoal rot of strawberry

Abstract

Macrophomina phaseolina, the causal agent of charcoal rot in strawberry, induces plant wilting and collapse. The pathogen survives through the production of microsclerotia in the soil and in strawberry debris. However, its management is difficult, and the disease has become an increasing problem for the strawberry industry. Physical, cultural, and chemical alternatives for integrated management of charcoal rot were evaluated in laboratory and field trials during the 2017-18 and 2018-19 strawberry seasons. In a laboratory trial, M. phaseolina microsclerotia were subjected to heat treatment and germination was inhibited at 52, 56, 80, and 95°C after 30, 10, 1, and 0.5 min of exposure, respectively. In infected strawberry crowns, microsclerotial viability was reduced after 5 min, regardless of temperature, whereas in the field, reduction was observed after 1 min. In field trials, charcoal rot incidence of inoculated strawberry plants transplanted into white-striped plastic-mulched beds was reduced to 20.8%, compared with 60.8% for plants grown in the black plastic mulch. On commercial farms, crop residue removal from infested areas reduced the M. phaseolina population in the soil but did not decrease charcoal rot incidence. Moreover, M. phaseolina propagule densities in the soil and in strawberry debris was reduced by fumigant application at crop termination but surviving propagules allowed the population to increase over the summer. Furthermore, preplant fumigation with metam potassium reduced soil population and charcoal rot incidence. Overall, the adoption of integrated approaches such as physical, chemical, and/or cultural methods played a significant role in reducing M. phaseolina inoculum and contributed to control of the disease in areas with high disease pressure.