By The Certis Team
Botrytis.
Just the mention of Botrytis is enough to strike fear in the hearts of Florida strawberry growers. It is one of the two most damaging diseases affecting strawberries. It is widespread, can develop unnoticed, and can wipe out a crop's economic return both at harvest and post-harvest. It has also shown high levels of resistance to multiple classes of fungicides.
A UF/IFAS survey of Florida growers found that more than 90% of strawberry fields were infected with Botrytis, making avoidance nearly impossible. The ease with which the disease can spread through nursery stock, wind, rain splash, and worker movement presents a significant management challenge. Growers surveyed estimated that they lost 5%-30% of their strawberry crop to Botrytis, with some reporting even greater losses.
Disease management is further complicated by the fact that Botrytis infections can develop undetected for weeks. By the time symptoms become apparent, it may be too late for preventive treatments. As a result, growers may be forced to rely on effective but resistance-prone conventional fungicides as curative treatments. This can mean using one of their limited curative applications earlier than planned because the disease has progressed beyond the point of effective prevention.
Treatment decisions are further informed by UF/IFAS predictive models, which help growers identify periods when conditions are favorable for high Botrytis infection and apply effective fungicides preventatively when needed. This approach helps growers time applications of the most effective chemical fungicide to periods of increased disease risk, which typically coincides with increased fruit production from late December through early March.
Biofungicides Excel Early and Late in the Season
These disease and resistance challenges highlight the value of fungicides in Botrytis management. In Florida strawberries, Botrytis infection is often a question of when, not if. Applying products such as OSO® (polyoxin D zinc salt) preventatively early in the season, paired with a non-ionic adjuvant as directed by the label, can help suppress Botrytis and protect the crop. OSO® belongs to FRAC Group 19, which includes fungicides with a unique mode of action that inhibits fungal cell wall formation. This makes OSO® a useful rotational partner in an integrated disease management program.
Starting the spray program with OSO 5% SC helps keep strawberry fields cleaner from Botrytis early in the season, reducing disease pressure before conditions become more favorable for infection. This proactive approach can lessen the burden placed on other effective fungicides, helping growers maximize their performance while minimizing the risk of resistance development associated with repeated use.
* Always consult product label for complete list of crops and diseases managed.
Botrytis is particularly challenging because infections during the growing season can lead to fruit rot after harvest, contributing to packing losses and rejected shipments. Making preventative applications toward the end of the season can help reduce disease pressure on fruit before harvest. Seasonal application limits on conventional fungicides can leave growers with fewer options when disease pressure increases close to harvest.
This is where OSO can provide additional value. With a zero-day preharvest interval (PHI), it can be applied up to the time of harvest to reduce fruit losses to Botrytis during transport and storage. By helping growers protect berry quality due to diseases, growers can maintain revenue and customer confidence.
By applying OSO at the labeled rate of 6.5 fl. oz./acre before the onset of visible disease, strawberry growers can incorporate preventative applications into their Botrytis management programs and add another tool alongside conventional fungicides.
Additional Product Resources
For more information about OSO fungicide and its role in disease management, read our blog from June: Grabs Fungi Right by the Chitin but Plays Well with Others
Additional Product Resources:
For additional information on OSO® 5% SC including technical specifications and labeled use directions, please refer to the resources below.
Always read and follow label directions. For a full list of protected crops and controlled diseases, visit the product pages and refer to the product labels.