Pest Management

Last week at the IAVAT conference, I had the pleasure of attending a professional development session at the College of DuPage about integrated pest management (IPM) in greenhouses.

The EPA defines IPM as “an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. IPM programs use current, comprehensive information on the life cycles of pests and their interaction with the environment.”

These are the four steps of IPM (as defined by the EPA):
Set Action Thresholds:
This step is when the pest’s presence is clear inside your greenhouse, and you now know you must take action to stop it.

Monitor and Identify Pests:
Since not all insects, weeds, and other living organisms need control, you must monitor and identify the pest to ensure you make appropriate decisions involving your greenhouse. This step removes the possibility that pesticides will be used when not needed and protects the greenhouse.

In this step, you manage your greenhouse to prevent pests from becoming a bigger threat than they already are. You can do this through different cultural methods:

  • Crop rotating
  • Selecting pest-resistant varieties
  • Planting pest-free rootstock

This last step involves evaluating and implementing an effective control method to mitigate the pest presence in the future. You will start with less risky controls such as:

  • Natural predators
  • Highly targetted chemicals (ex. pheromones that disrupt pest mating)

If after further monitoring, identification, and action thresholds you can conclude that the less risky controls are not working, you can move to more risky controls, such as spraying pesticides.

Always remember: Broadcast spraying non-specific pesticides is always a last resort.

For more information about IPM go to this article: Integrated Pest Management (IPM) Principles | US EPA

Unfortunately, we have seen some pests in some of the MARSfarm units at HQ. Pests that are harmful to greenhouses only come from the outside. Since our greenhouses are meant to be in a classroom, indoors, pests are normally not an issue. They popped up in our units growing Swiss Chard. We got the Swiss Chard from a nursery, which brought aphids into our system.

Here are some photos of our (sadly) aphid-covered plants):

This is a photo of one of the Swiss Chard leaves covered in aphids. The white dots are aphids

This is a photo of the aphids up close.

Here are some common pests and some less risky controls that you can use:
Pest - Aphids:
Aphids are very small and burrow into the veins of leaves and suck out all the water from them. Since they reproduce very quickly, they can be a huge problem for your greenhouse.

This is a photo of Aphids.

Solution - Aphid Parasitoids:
Aphid parasitoids are tiny wasps, about 1/10 inch long, that sting aphids putting one of their eggs inside the aphid in the process. As the egg grows and eventually hatches the aphids die. Crazy right!! These wasps are so tiny that you do not need to worry about them stinging humans. Aphid parasitoids only work to kill aphids and are pretty successful.
This is an image of an aphid parasitoid stinging and aphid, ultimately implanting its egg inside of it.

Pest - Thrips:
Thrips are small insects that cause leaves to become papery and distorted. They grow wings when they need to find a new place to feed. They stunt plant growth in the process. You can spot if a plant has been attacked by thrips, by spotting tiny pale spots on the leaves (typically on the underside of the leaf). Thrips love pollen, so you can normally see them in pollen-heavy areas.

This is an image of thrips.

Pest - Spider Mites
Spider mites bruise plant cells with their small mouthparts and ingest the sap, ultimately killing the plant.

This is an image of spider mites.

Solution - Predatory Mites:
Predatory mites are tan-colored and are found on the underside of leaves. They are effective in killing and preventing thrips. They should be applied at the first sign of thrips. Appling these mites near pollen-heavy areas will make them most effective. Predatory mites also work very well against spider mites.
This is an image of predatory mites.

The solutions to these pests can be expensive (hundreds of dollars for a bottle of aphid parasitoids). Becuase we don’t run into pests very often, and their control measures are expensive, we just got rid of our Swiss chard plants (I know very sad). We then cleaned the unit they were growing in and made sure that no aphids were present.

If you have any other solutions or questions about pests feel free to share them on this thread.