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The Challenges of Managing Pests and Diseases in Retail Settings

Wed, May 22nd, 2019, created by Nick Flax
Greenhouse growers work tirelessly each year to produce high-quality plants for spring sales. Of all of the different factors involved in growing bedding plants, pest and disease management is one of the most important. Though monitoring for pests and diseases and taking corrective action ends at shipping for most wholesale floriculture growers, it is only the beginning for retailers. 

During the frenzy of spring retail sales, it is easy to overlook pests and pathogens. Understandably, most retailers are focused on assisting customers, crowd control, and loading up plant material into peoples’ vehicles. However, if pest and disease management is not maintained as a priority amidst the chaos, excellent-quality bedding plants can quickly become unsalable. Several of my recent site visits here in Pennsylvania (PA) have provided some strong reminders as to just how quickly things can take a turn for the worse if pests and diseases are allowed to go unchecked in a retail setting.

The photo above was taken at a garden center in PA on Mother’s Day weekend. These vinca (Catharanthus roseus) in 4-inch pots and the two adjacent racks full fo vinca were completely enveloped by grey mold (botrytis). How did these plants get so badly infected? For starters, much of the spring season here in PA has been cold, rainy, and generally overcast. When free moisture on leaves is abundant, temperatures are cool, and spores are present, pathogens like botrytis will strike. This grower has faced similar challenges in previous years and was at a loss as to how they can prevent this from happening again in the future.

In many ways, pest and disease management in retail settings can be substantially more challenging than in wholesale production facilities. For example, many of the most effective pesticide chemistries used in commercial greenhouses can have relatively long restricted entry intervals (REI). A production house with limited foot-traffic can be closed down for 12-48 hours far more easily than a retail space where, ideally, customers are coming and going constantly all day long. This can greatly limit a retailer’s chemical control options during a severe pest or disease outbreak. Similarly, managing cultural and environmental factors can be more challenging for retailers. In a production greenhouse, free moisture in the plant canopy can be managed and reduced by adjusting watering practices. However, when plants like the vinca shown above are being held on racks outside, retailers are at the mercy of whether it will rain for a few hours or a few days in a row.

To reduce the likelihood of and manage pest and disease flare-ups in retail-ready bedding plants, retailers should consider: 
1) Cleaning up dead/dying leaves and spent flowers very regularly to reduce disease inoculum potential, 
2) Increasing spacing of plants during cool and wet, and/or high-humidity conditions,
3) Developing a list of “soft” chemistries and biological controls that can be implemented preventatively or with a short REI (4-8 hours) to spot-treat for pests and pathogens, and
4) Creating a quarantine area away from primary retail spaces where stronger chemistries can be used without having to close off the main retail footprint.

About the Author:

Nick Flax

Commercial Horticulture Educator, Penn State Extension

Nick Flax is a Commercial Horticulture Educator with Penn State Extension, based in Doylestown, PA. His background is in greenhouse crop physiology, with an emphasis on plug production, annual bedding-plant production, seasonal potted crops, and container-crop production using biocontainers. Nick has industry experience in wholesale young- and finished-plant production, retail floriculture, and has a strong background in pest and disease management, biological IPM, and controlled-environment crop research.

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