Hurricane/Tropical Storm Helene affected much of Georgia’s agriculture, including blueberries. Both wind and extreme rainfall caused their share of issues. In some parts of Georgia’s blueberry-growing region, wind damage (resulting in broken limbs, lost leaves, and blown-over bushes) seems to have caused most of the damage, while in other areas, extreme rainfall seems to have flooded fields, washed away beds/plants, and exposed root systems. From a blueberry disease management standpoint, what to do now will really vary a lot by location.
In areas that got a lot of rain but relatively minor damage caused by wind, the major disease concerns are similar to those I mentioned in my blog post a couple months ago following Hurricane/Tropical Storm Debby. These include concerns with Phytophthora root rot, algal stem blotch, and leaf spot diseases. While we are getting closer to the end of the growing season for blueberries, we typically recommend continued maintenance of plants in southern Georgia through the end of October, when the plants begin moving from actively growing and setting buds into a time of plant dormancy. As such, and especially given the recent rainfalls, control of these diseases is likely to remain important for the next 4 weeks or so in southern Georgia. By contrast, in the more northerly parts of the state where plants stop growing and enter dormancy earlier, it may be too late for management interventions to have substantial value against these diseases.
In addition, in any areas where wind damage occurred (whether there was a high level of rainfall or not), limb and stem breakage (and subsequent pruning operations to remove broken or damaged plant parts) may result in wounds on plants that can serve as entry points for fungal pathogens such as Botryosphaeria. On blueberry, these fungi can cause Botryosphaeria Stem Blight disease. Fungicide applications aimed at protecting wounds on affected plants may be beneficial. For this purpose, the application of broad-spectrum fungicides, such as Pristine or Switch, are most likely to be useful.
Please note that for plants that have blown over and are being reset or have major stem or limb breaks, whether they recover or not will depend on a lot of factors with diseases being a (possibly minor) part of the equation. That being said applying fungicides to protect damaged root systems from root rots, such as Phytophthora, and open wounds from stem blights, such as Botryosphaeria, will certainly not hurt (and may help) in the recovery process.
Additional information regarding Botryosphaeria stem blight, its symptoms, and management recommendations can be found below:
Botryosphaeria Stem Blight
Botryosphaeria stem blight is a destructive disease affecting production of both highbush and rabbiteye blueberries in the southeastern U.S. This disease can cause particularly severe losses during the first two years after planting, but can also affect older plantings as well. It is now known that Botryosphaeria is actually a disease complex, caused by more than one fungal species. These fungi generally attack through wounds or succulent tissue (e.g. “suckers”) with some apparently more likely to attack stems and others more likely to attack the crown. Nonetheless, regardless of the particular fungal species involved, disease symptoms and current management options are generally similar.
Symptoms from Botryosphaeria infection mimic extreme drought stress due to the fact that the fungal pathogen infects the vascular system of the plant and disrupts water flow. Accordingly, the most visible symptoms of Botryosphaeria are the rapid blight of infected canes. When this rapid blight occurs on only one or a few canes on a plant, it is called “flagging” (Figure 1A); however, when dieback reaches the crown of the plant, entire plants can die rapidly. Brown and dried leaves initially remain attached to the stem, making stems and plants affected by Botryosphaeria easy to spot amidst their healthy counterparts (Figure 1B). To confirm that Botryosphaeria is the cause of cane death, growers can cut into affected canes to look for pecan-brown wood discoloration in cane cross-sections (Figure 1C). This wedge-shaped discoloration typically occurs where the fungus has entered the plant xylem.

Fungal infection of the xylem makes infected plants extremely susceptible to drought stress. Accordingly, symptoms often appear more frequently during hot and humid late summer conditions. Nonetheless, fungal infection can occur throughout the year in the warm, humid southern climate, making prevention and management of this disease a year-round issue for blueberry growers.
Once plants are dying from Botryosphaeria, options for control are generally very limited; therefore, prevention is essential. Tissue cultured plants do not generally have Botryosphaeria, but the fungi that cause this disease are found virtually everywhere, meaning that plants can develop the disease after as little as two years in the field. Preventing plant stress and injury can be critical for limiting disease establishment. Balanced plant nutrition and water are important. Slowed rates of nitrogen fertilization can make the plant less succulent and therefore less susceptible to this disease. To allow plants to harden off naturally, it is recommended that nitrogen fertilizers not be used after late August or early September (unless clearly needed). Botryosphaeria organisms often enter through wounds, so reducing plant injury can reduce the occurrence of this disease. Wounds may occur from various sources including cold injury, mechanical injury, pruning and hedging, and mechanical harvesting. Herbicide contact with green stems can also lead to wounds that can serve as entry points for Botryosphaeria – and paraquat usage in rabbiteye production has been reported to increase the incidence of stem blight.
Crown infections with Botryosphaeria are especially difficult and/or impossible to address, and when the infection reaches the crown, the plant will most likely die. For plants where only individual canes are affected, these canes should be cut out to a point 12 inches below the last dead wood. To prevent inoculum carryover on pruning equipment, shears should be sterilized between cuts with 10% bleach. Pruning or hedging when 2-3 days of dry conditions are expected can help reduce the likelihood that the fungus will re-infect the newly wounded tissue. Also, after each day of pruning or hedging, application of a broad-spectrum fungicide, such as Pristine (pyraclostrobin+boscalid) or Switch (cyprodinil+fludioxonil), may help to protect the new wounds. To eliminate residual fungal inoculum found on the removed plant material, prunings should be destroyed as soon as possible, ideally by burning or burying. Alternatively, flail mowing of the pruned material can help speed drying and decomposition. It is important to emphasize that there are no foolproof methods for eliminating Botryosphaeria once the disease begins to take hold. Rather, there are only stop-gap measures at best.