There is a lot of information out there telling you how to get rid of pests in a hydroponic garden, which pests are the worst, which are most common and what to do about them and when. I can’t, however, find anything that tells you what types of pesticides there are, how they affect the plant, how they work and if they can have any ill effects on the plants, the yields or even human health. Considering I consume what I grow, as I’m sure you do as well, trying to cure one problem might inadvertently create another one, possibly a much bigger one that could affect our long-term health.

Defining Systemic and Non-systemic Pesticides

The definition of systemic is something that spreads throughout and effects something as a whole, in this case we are talking about a plant. The general rule of thumb in hydroponics and indoor gardening is that non-systemic pesticides are okay and systemic are not. Why?

Non-systemic pesticides are thought to be okay as they can be removed/flushed from the plant before harvest. This makes the produce from the plant clean from pesticide chemical tainting and thus better for human consumption.

"Systemic pesticide chemicals designed to kill insects will be present in the plant’s flowers, fruits and seeds, essentially poisoning them."

Systemic pesticides are thought to be unsuitable as they affect the plant as a whole. Whether they are taken up via the roots or from absorption through spraying the leaves, pesticide chemicals cannot be removed/flushed from the plant. Once they have been taken in by any part of the plant they are present in and affect it as a whole. Systemic pesticide chemicals designed to kill insects will be present in the plant’s flowers, fruits and seeds, essentially poisoning them.

Most systemic pesticides used in hydroponic growing are hazardous to humans, so once used on a plant, that plant and anything that plant produces (including seeds) will not be fit for human consumption. Some of the chemicals are known to cause, amongst other things, cancer, birth defects and sperm mutation. Also, it affects the pollen of the plant. This has had a huge negative effect on pollinator populations with bees being a prime example. Systemic man-made pesticides have diminished bee populations to critical numbers around the globe.

The Three Main Pesticide Groups

There are three main common groups of pesticides that are used in hydroponics and indoor gardens:

  • Contact pesticides - mainly non-systemic
  • Surface pesticides - mainly non-systemic
  • Uptake pesticides - mainly systemic

"Pesticides can be dangerous and the bottom line is it is important the retailer provides you with accurate and timely information about the product."

All of these can be either systemic or non-systemic, however, normally they fall under the above categories. Unless you ask at the purchase point you won’t know. If you do ask and the sales associate doesn’t know or is not sure, my advice would be to hold off until you know for sure. Pesticides can be dangerous and the bottom line is it is important the retailer provides you with accurate and timely information about the product.

  • Contact pesticides. These types of pesticides are designed to be sprayed or applied directly to the unwanted pests. This contact is where it will have the necessary results on the pest. These pesticides are designed to kill pests on contact, and there doesn’t appear much thought has been put into the effects the excess spray that ends up on your plants may have. Contact pesticides are normally non-systemic but can be systemic. Excess spray can be absorbed by the plant through the leaves and the stem where it will remain in the tissue of the plant. Contact pesticides are normally pretty harsh stuff. They can leave a chemical taste in the fruit of the plant if applied while the plant is flowering/fruiting.
  • Surface pesticides. This is where the plants are treated with the chemical pesticide (normally via a spray). The chemical coats the plant surface and kills the insect from the insect having contact (whether that be the pest eating thought the pesticide to get to the plant or simply walking over the treated surface) with the affected area or forming a repellent/barrier between the plant and the pest. Again, these pesticides aren’t designed to be taken into the plant systemically but nevertheless some do, as prolonged surface exposure to the chemical and the plant is common. This is especially true with indoor gardening and hydroponics as there tends not to be any rain, which would in a natural outdoors environment help to clean the plant of any surface pesticide chemicals.
  • Uptake pesticides. These pesticides are nearly always systemic. They are called uptake pesticides because the pests take up the pesticide directly from the plant. These pesticides are normally fed to the plant viscerally, but they can also be applied via a spray. The premise of this type of pesticide is that they are systemically taken in to the whole of the plant, essentially turning the plant poisonous to the pests that are feeding off them. As mentioned previously, this not only poisons the main plant but also poisons its fruits, seeds, leaves and even the pollen. The long-term consequences are toxic soil and any run-off through the irrigation system will negatively affect the environment and be harmful to creatures. The discarded portions of the plant, some of which are used to feed livestock, tilled back into the soil or composted will also carry a toxic signature.

Conclusion

Every grower will have pests at some point and what you do about them is up to you. If you do decide to use pesticides, consider their effects on the plant’s health, your health and the environment’s health, and consider less harmful options that can perform the same task. Hopefully this information will help you to make an informed and responsible choice when buying pesticides.