Keep Out Greenhouse Pests
May 1, 2010 
Sometimes the simplest things can make a big difference in the success of pest control in greenhouse structures. Steps to keep these insects out of the greenhouse are an important place to start in the never-ending battle.
In vegetable production, indoors or out, sanitation is preached as the very foundation of fighting disease and insect pests. Remove weeds inside and around the greenhouse, as they may attract and harbor pests.
Many growers have had success using weed mats that cover a 10-foot area outside the perimeter of the greenhouse structure.
A well-maintained grass area around the greenhouse is about as good as anything to help avoid attracting unwanted pests. Take an inventory of plants in the vicinity of the house. If they are ones that attract major pests, it makes sense to remove or replace those plants.
Lock It out
Having a small room connected to the entrance of a greenhouse will serve as an airlock area. Using this double-door approach can be helpful in excluding pests. Those entering can brush their shoes off with a shoe brush before entering airlock, and then, while in the airlock, dip their shoes in a sanitizing footbath before entering the greenhouse. Many modern greenhouses have full-body sanitizing misters to sterilize potential threats to the crops inside.
Screen It In
Anywhere there is an opening in a greenhouse, pests will come in. Perhaps one of the most effective tools in excluding pests is screening that keeps the bugs out and allows air in. But, growers should be aware of insect screening sizing needed for particular pests. For example, aphids require openings in the screen no larger than 350 to 450 microns, while thrips require even smaller openings no larger than 215 microns. To illustrate how small that is, there are 1,000 microns in a millimeter.
Because the holes are so tiny, attention should be paid to airflow into the greenhouse. If it is too restricted, the surface area might need to be increased or fan size may need to be increased. Finally, the screens should be cleaned periodically to keep airflow steady.
Blinded By The Light
Researchers at the North Florida Research and Education Center in Live Oak have been looking at the effect of highly-reflective, metalized mulch in fighting key vegetable pests. Flying insects, such as thrips and whiteflies, orient themselves to the sun, so the reflective nature of the mulch disorients the pests.
In one test, the metalized mulch was placed over the 10-foot ground weed mat on the perimeter of the greenhouse. If the mulch is laid on bare ground, kill off weeds to place on as smooth a surface as possible. The mulch is thin, delicate, and easily picked up the by the wind, so it is best to apply when winds are low.
In their own experiments, researchers found rolling the tape and fastening it as they went works better, rather than rolling it out all at once and then fastening. They used clear duct tape on overlapping layers, taping it onto the weed mat. On the seam of the two strips, they applied fiberglass tape and then pressed a round ground pin through the fiberglass tape at about 1-foot intervals to secure the mulch to the ground.
The research has shown 10-fold or better reduction in whitefly populations in greenhouses surrounded by the highly reflective mulch when compared to houses with no mulch.
Entomologists agree these techniques work best in combination with one another, not alone. Even when utilizing the best exclusion techniques, pests will make their way into greenhouses, so scouting remains a must in any vegetable production greenhouse.