How do greenhouses affect pesticide use?

Question

Is the environmental impact of pesticide use on greenhouse crops substantially different from the impact of pesticide use in open-air crops?

I imagine that, at least in theory, a greenhouse should have the opportunity to keep pests out by being a closed environment. When pests are kept out in the first place, less or no pesticide should be needed to kill them. Or, if pesticide is being used, it may be less likely to escape into the natural environment.

Does my imagination have anything to do with reality?

Answer 1

To a general question this general answer: I don't know, but in general I don't think so ;-) but then again, ...

First: a greenhouse is not a closed environment. It is aerated (insects can come in and go out) and (unless the water is drained in an isolated way) water escapes via the soil (residue pesticide escapes also).

Second: pesticides can be a lot of things: herbicides, insecticides, fungicides, bactericides etc. depending on what is bugging you.

A greenhouse doesn't keep any pests out (unless you mean rabbits maybe?) and can create its own kind of problems (it is a hot and moisty environment that is ideal for some insects and fungi).

The only thing is: when you have to spray pesticides of any kind, there is some direct protection for neighboring parcels (that don't get acutely polluted).

Also, if you have to use biological biocides (like wasps) they are more likely to stay in the greenhouse (not sure).

Answer 2

Weed control is easier in greenhouses, so herbicides aren't used much.

However the higher humidity levels and more constant temperatures make both insect and fungi much larger pests.

The expense of operating a greenhouse also pushes to maximize production per square foot, so the use of fertilizers is increased. I would expect more pesticide use per tonne of product in greenhouse production.