Hydroponic Pesticides And Your Indoor Garden


There is a lot of information out there telling you how to get rid of pests in a hydroponic garden. For example, which pests are good, which are most common, and what to do about them and when. Considering I consume what I grow, as I’m sure you do to, trying to cure one problem might inadvertently create another, possibly one that could affect our long-term health. So, when it comes to using an insecticide, I prefer one that has a short life span. One that can be washed off, have little residual affect and can be flushed from the plant prior to harvest.


What does systemic mean?  A pesticide that is absorbed and circulated by a plant or other organism so as to be lethal to pests that feed on it. That’s great! But the problem is that they are absorbed into the roots and tissue of a plant and become part of the plant. At harvest time you can ingest some of that pesticide along with that tomato you grew. As a general rule in hydroponics, non-systemic insecticides are fine but systemic are not.  

Systemic pesticides are in the plant, not on it. When we make the plant itself poisonous to predators, one has to wonder what (or who) else it’s poisoning.

Most systemic pesticides are hazardous to humans. So once used on a plant, that plant and anything that plant produces (including seeds), will not be fit for consumption. In addition, it can affect the pollen of the plant. (Misused systemic pesticides have had a negative effect on pollinator populations, namely honeybees.)


There are three main groups of pesticides used in hydroponics:

  • Contact, mainly non-systemic
  • Surface, mainly non-systemic
  • Trans-located, mainly systemic


Bug spray

These types are designed to be sprayed or applied directly to a pest. They are designed to kill on contact. (Think of a can of Raid for killing ants). Excess spray however can be absorbed by the plant through the leaves and stem.


These types of products are for treating the plant via a spray. The chemical coats the plant foliage and will kill an insect when it walks over the treated area. It will also kill the insect if it decides to nibble on the leaves. Again, these pesticides aren’t designed to be taken into the plant systemically but some do. This is especially true with indoor gardening as there tends not be be any rain, which normally would wash the plant surface of the chemical.


Aphids on leaf


These pesticides are mainly of the systemic variety. As mentioned, they can be placed via a spray and then absorbed into the plant as a whole thus turning the entire plant poisonous to the pests. They usually have a longer residual affect which is why they can affect not only the plant but fruit, seeds and pollen.

The bottom line?  For the most part every grower will have an unwanted pest. If you decide to use a pesticide go with the least harmful, the Contact type first. If you would like more information on using more organic pesticides, read my Blog entitled “Organic Hydroponics & Pesticide Use” October 2016.

Questions? Comments? Send us an email. Thanks for Reading!

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1 Comment

  1. Kim on December 14, 2017 at 9:01 am

    Hydroponics will change many things regarding the safety of our food. I was unaware of the risks of those systemic types of pesticides.

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