Macrophomina phaseolina, the causal agent of charcoal rot, affects strawberry crowns, inducing plant collapse. The fungus survives in the soil through the production of microsclerotia and is usually controlled by preplant fumigation of soil. However, in the 2016 to 2017 Florida strawberry season, even after soil fumigation, about 30% plant mortality still occurred in plastic-covered beds that were used for a second season and where crop residue (mainly old strawberry crowns) was disposed of between beds. Therefore, this study was conducted to determine if M. phaseolina can survive on strawberry debris over summer in Florida and if so, verify whether strawberry debris might act as a source of inoculum for new transplants. Crowns from the previous season were collected from commercial farms where charcoal rot had been reported, and M. phaseolina was recovered from all samples. In a research field, infected crowns were buried in the soil at different depths and retrieved every 2 weeks during the summer. After 8 weeks, M. phaseolina could be recovered at all depths. Moreover, inoculation of strawberry plants by drenching the soil, dipping roots, or spraying leaves with a M. phaseolina microsclerotial suspension from pure cultures or infected crowns produced symptoms with differences in incubation periods depending on cultivar susceptibility. Furthermore, infected crowns disposed of in the aisles between beds or buried next to new transplants of cultivars Strawberry Festival, Florida Beauty, and Winterstar induced charcoal rot, with the level of aggressiveness depending on the cultivar susceptibility and inoculum placement in the field.

Management of Macrophomina phaseolina, causal agent of charcoal rot in many crops worldwide, including strawberry, has become more challenging since the phase out of methyl bromide (MeBr). The search for a fumigant equally effective as MeBr to control soilborne pathogens has been extensive. Allyl isothiocyanate (AITC), a biofumigant recently registered in the United States, was evaluated at different rates, formulations, fumigant combinations, and application methods in the fall of 2014 and 2015 at two research facilities in Balm and Dover, FL. The efficacy of treatments was determined by evaluating the survival of M. phaseolina inoculum on infested corn-cob litter buried in bags 7.6 and 20.3 cm deep in the center, and 7.6 cm deep in the side, of plastic mulched raised beds. The biofumigant was shown to be more or as effective in reducing populations of M. phaseolina in the soil compared with standard fumigants, such as chloropicrin and 1,3-dichloropropene with chloropicrin. Thus, AITC is a promising biofumigant alternative for managing charcoal rot of strawberry, particularly in organic production systems, and should be evaluated for the management of other soilborne pathogens.

Strawberry production in Florida and South Carolina is affected by two major diseases, anthracnose fruit rot (AFR) and Botrytis fruit rot (BFR), caused by Colletotrichum acutatum and Botrytis cinerea, respectively. The effective management of both diseases traditionally relied on weekly fungicide applications. However, to improve timing and reduce the number of fungicide sprays, many growers follow the Strawberry Advisory System (StAS), a decision support system for forecasting fungicide applications based on environmental conditions and previously developed models. The objective of this study was to perform a meta-analysis to determine the effectiveness of the StAS for AFR and BFR management compared with a calendar-based spray program. Thirty-nine trials were conducted from 2009 to 2014 in Florida and South Carolina commercial strawberry fields. Meta-analysis was conducted to quantify the treatment effects on four effect sizes, all based on the difference in response variables for StAS and the calendar-based treatments in each trial. The mean difference in BFR incidence, AFR incidence, yield, and number of marketable fruit between the two treatments was not significantly different from 0 (P < 0.05). However, the number of fungicide applications per season was reduced by a median of seven when using the StAS, a 50% reduction in sprays compared with the calendar-based approach. Effect sizes were not influenced by location or the favorability of the environment for disease development. These findings indicate that use of StAS in commercial fields is effective in controlling fruit rot diseases with no reduction in yield while substantially reducing fungicide applications.