Weed control in greenhouse:
Prevention: Keep weed  (seed, rhizomes, tubers, etc.) out of the greenhouse by using sterile media, introducing only "clean" plant materials, and controlling the weeds outside of the greenhouse. Where possible, screen vents and other openings to limit the introduction of windblown seed as well as flying pests. Again - Clorox can be your best weapon!
Use a 1:10 solution to spray down floors, growing benches, drip containers in and wipe propagation tools. Clorox is a very corrosive product. Zerotol is another option available from vendors like Griffin Greenhouse Supplies and BWI.

Controlling Existing Weeds
If the weeds are already established in the greenhouse, they can be killed in the following ways:
1.Manual removal (6th graders love this!)
2. Empty the greenhouse during the hot summer months and allow weeds to dry up (solarization)
3. Treat with a postemergence herbicide
Make sure you use a postemergence herbicides labeled for use inside greenhouses. There are very specific restrictions on the use of herbicides in greenhouses. With one exception, the products described below are only for use under benches, in walkways and around the foundation of the greenhouse. They are not for use in pots or ground beds where crop plants are growing. Read the label and carefully observe any precautions. Always wear personal protective equipment when applying pesticides in a greenhouse. If the postemergence is in a liquid application form make sure your air circulation fans are turned off during the application. Avoid aerial drift by using a low pressure, large droplet type nozzle.

Preventing Weed Seed Germination
BareSpot is non-selective residual herbicide may be used under benches, in gravel walkways and around the foundation of the
greenhouse. The active ingredients in Barespot are sodium chlorate and sodium metaborate. Do not allow the product to come in contact with containers or greenhouse ground beds. After application, water-in to activate the herbicide.

Outside of the Greenhouse
The primary objective of weed control outside the greenhouse is to eliminate a major source of airborne weed seed and to prevent
perennial weeds such as bermudagrass from growing under the foundation and into the greenhouse.

Insecticide Basics for the Pest Management Professional - Educational Resource

GGSPro Tech Tips: http://www.griffins.com/ggspro-techtips

This is a great resource. Use the link above to answer many common greenhouse pest issues. There’s way too much information on this page, so I would suggest searching within the page (Ctrl F) to find what you might be looking for.

Good Greenhouse Rules:
Here are some other good rules for your greenhouse.
No smoking or tobacco products in greenhouse. If you or students do smoke or use tobacco products, disinfect your hands before entering the greenhouse to prevent spreading tobacco mosaic virus.
Clean your boots/shoes before entering or change into a clean pair of greenhouse shoes or boots.
Keep hose ends off the floor.
Discard pet plants, unnecessary plants, infested plants, and weeds under benches.
Control ants as they can harbor and protect aphids, mealy bugs and scales.
Always wear closed toe shoes when working in the greenhouse.

Josh Allen 
North Region Ag Education
1420 Experiment Station Road
Watkinsville, GA 30677
706-202-0770 cell