Fall is for disease control

The autumn months may be when plant sales slow down at the nursery. But growers must remain vigilant, because there are plenty of ways plant diseases can sneak in while you’re thinking about pumpkin-spiced coffee or corn mazes.

Take a little off the top.

For disease prevention in perennials, it’s a good idea to reduce the amount of foliage that is exposed through the winter. Once you determine a crop is closing out for the year, cut it off at the soil line if you can.

“Anything you can do to reduce the amount of foliage that is sitting there that is going to die is a good thing,” says Margery Daughtrey, senior extension associate with the Long Island Horticultural Research & Extension Center. “Otherwise, you’ve got a conduit for botrytis to move into the crown of the plant during the winter.”

Botrytis is active at cool temperatures, even as low as 32° F. So even though the plant is shut down for the winter, the disease is still active. You don’t want an outbreak of botrytis developing under those circumstances. Manage your moisture. Just like the growing season, you want to keep your foliage dry. Set up your moisture management system to provide sufficient moisture — but not too much — during the winter months.

Growers should have their maintenance of persistent problems under control before football season starts, and not expect a fungicide application to hold for an entire winter.

“You can’t make up for a season’s worth of negligence with a treatment before you put them to bed for the winter,” Daughtrey says.

photo | Adobe Stock © wiha3; Valeriana Y

Keep an eye on your heat.

Try to reduce the amount and extremity of temperature fluctuations your plants experience. Even without a pathogen involved, plants can die because of too much fluctuation between cold and warm. That’s why it’s important to open the poly house up so you don’t have a buildup of heat.

Growers might just open the ends or cut holes in the sides. Daughtrey says there is a certain artistry to this practice, and it’s very regional. The grower’s experience is often their best guide of when the time is right.

Second-guess that fall vacation. Many growers take time off in the autumn. After the point in fall when sales slow down but before winter really sets in — well, it’s as good a time as any. And we’re not saying not to take some time off. You’ve certainly earned it. But it’s important to continue your maintenance through fall, before you have the plants bedded down for the winter. Daughtrey says if you have something like a leaf spot problem or a powdery mildew problem, keep the control up until the time that you are putting them under winter conditions.