How to Eliminate Pests in a Fall Greenhouse

It’s November, which means that the last dregs of fall are fading fast. US growers in zones three and four have likely already experienced some freezing temperatures overnight. Wherever you are, temperatures are dropping, which means that garden pests are looking for a place to take shelter and get away from the cold. 

Unfortunately for you, your greenhouse is the perfect place for pests to shack up for the winter!

Regardless of what you do, a greenhouse will inevitably attract pests during the colder months. By definition, a greenhouse is warm, climate-controlled, and usually has a high humidity level relative to the outdoor environment. Don’t fret! There are ways to minimize pest attraction and manage existing infestations.

Get Rid of Dead Plant Matter

Truthfully, the best time to clean a greenhouse for winter is in September or October, but November is a good case of better late than never. Look at your forecast and select the warmest, sunniest day possible (even if those are in increasingly short supply in the northern US) for cleaning. Before you clear out your greenhouse, check any plants that will be overwintered in the greenhouse. Are they looking healthy? 

If you need to prune away unhealthy or dead branches/stems, now is the time to do it.

Once your plants are pruned, move everything outside. You’ll inevitably have some dead plant matter on the ground, and you’ll likely have bits of mold tucked into the dark corners of your greenhouse. Grab a hose and spray it down! After power washing away the obvious plant matter, apply a cleaner to the structure of the greenhouse. Make sure to pay attention to corners and recesses that offer shade - these areas are hotspots for pest breeding and fungus. Windowsills are another area to focus on.

Tip: Check out SaniDate® All Purpose Disinfectant for a reliable all-purpose cleaner. 

After you’ve applied the cleaner, make sure to wait at least 15 minutes to air the greenhouse out before bringing plants back in.

Seal and Secure

During the cleaning process, keep an eye out for noticeable gaps in your greenhouse structure. Simple repairs on a plastic frame can be done with greenhouse repair tape, which will also be labeled as a polyethylene tape. Make sure the tape is UV resistant. 

If the damage is too severe, we recommend talking with professionals to determine your next step. Some greenhouses you can simply replace one wall, while others might require a complete refitting. As common sense implies, sealing up your greenhouse limits the amount of entry points for pests.

Keep Plants Apart
It can be tempting to fill your greenhouse to the brim during the winter months. After all, where else are you going to grow? However, putting too many plants in your greenhouse can lead to more harm than good. Pests can easily move from plant to plant when leaves from two plants overlap. A single pest can multiply rapidly in an overcrowded greenhouse.

Fight Back!
Keeping your greenhouse free of plant matter and sealed up tight does a great job at preventing most winter infestations, but insects are called pests for a reason. They have a nasty habit of showing up exactly where you don’t want them. When pests do breach your first line of defense, make sure you’re equipped to fight back. Aphids are a pest no matter what time of the year, and they’re more than happy to invade your warm greenhouse.

Sticky Traps are a greenhouse essential when it comes to monitoring pest populations. However, to keep pests like aphids under control, check out biological pest control, such as the green lacewing. Keep in mind that green lacewings are most effective in a setting with temperatures between 67-90 degrees F and relative humidity of at least 30%. Check out this article for more information about maintaining a green lacewing population and using them as a means of pest control.

From Robin @ARBICO Organics