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greenhouse pests

How to Manage Greenhouse Pests

In my last article I introduced what it takes to work in a greenhouse. While for the most part it is a pretty simple work environment, there is one aspect that warrants a more in-depth discussion: greenhouse pests. It doesn’t matter if the pest is an insect, virus, or bacteria, it can very quickly bring a greenhouse to its knees if those working inside aren’t extremely careful. Luckily, as long as you have a watchful eye, managing pests shouldn’t be too big of a headache.

Prepare for the Inevitable

Greenhouses are only semi-contained, meaning there are plenty of ways for the outside to get in. Whether it is through the vent in the ceiling or on the uneducated student worker, pests almost always end up in the greenhouse from time to time.

As a greenhouse worker, you need to be prepared for it. Look up the common pests in your area, and especially those known to infect greenhouses. Some of the most common are aphids, thrips, and fungus gnats. Know what they look like and not just as adults. My lab has a picture of all the life stages of the major players printed out in the lab at all times. Also, familiarize yourself with the infection symptoms, which can vary widely depending on the type of pest. Make sure you know what to look for when you are scouting.

Once you are familiar with what the pests (and their symptoms) look like, put that knowledge to use. Every time you are in the greenhouse watch out for the symptoms that you familiarized yourself with earlier. At least a couple times a week, make sure you thoroughly inspect your plants and take note of anything that is out of order. Sometimes it is the beginning of an invasion, sometimes it can be a clue that the nutrients are off, and sometimes it’s just a result of greenhouse growing conditions. In any case, it’s a good practice to be in tune with what your plants are doing. If it does happen to be pests, the earlier you catch, it the better.

Take Swift Action Against Greenhouse Pests

If your inspections catch something, jump into action immediately! If you are fast enough you can contain the infection to just a few plants.

First, notify your greenhouse manager in charge of any sprays and maintenance. They should know, and be able to coordinate, the appropriate course of action for the pest in question. Next, let anyone in your greenhouse know about what you found. This lets them know that they should be keeping an eye out for the pest on their plants as well. Lastly, let anyone in any connected greenhouses know as well. Sometimes pests can get between seams in the dividing glass separating rooms, so it is good practice to let your greenhouse-mates know to keep an eye out.

Make sure you know what the greenhouse worker will be spraying/applying, as well. Make sure that the treatment is designed to treat the specific pest you are dealing with, and know how often it needs to be applied. If it is supposed to be re-applied, make sure you remind the worker when that time comes. Keep an eye on resistance as well. If you are using the same active ingredient every week to kill off spider mites and it isn’t working, talk to your greenhouse manager about switching to something else.

It should also be noted that you shouldn’t go into any other greenhouses after you enter one that has pests. If you have multiple greenhouses or growth chambers, any that have a pest in them should be entered last. Pests love to hitch rides on clothing and lab equipment, so consider anything that enters the greenhouse to be “contaminated”.

Stay Vigilant

Once the chosen treatment has been applied, make sure it has been effective. Keep checking your plants every day to make sure that the treatment worked, and that nothing got missed. Insects sometimes like to hide in the whorls and undersides of leaves and can be missed by foliar sprays so don’t assume that everything was killed even if you find dead insects after a spray. Also make sure that you are watching for all the different life stages of the pest you were dealing with. It’s possible that you might not be seeing adults anymore, but there still could be larvae roaming around. Once you have gotten the infection under control, let those you communicated with earlier know and tell them what was effective.

At this point, you can return to your normal scouting routine. Don’t get lazy! It’s easy to fall into a trap of assuming your plants will be pest free because they were the last couple of weeks. Keeping your plants pest free is an everyday task, but in reality is an easy one!

Image credit: Peter & Michelle S

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