How to maintain a pest-free garden with an organic IPM regime (Integrated Pest Management)

“Integrated pest management (IPM) is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimises risks to human health, beneficial and nontarget organisms, and the environment.” – University College Davis

Don’t buy cuttings, start from seed – It’s hard to spot when they are young and not very diseased. It is only when you start to see the slow signs of growth that you have a proper look. To an inexperienced eye, it can be hard to spot signs of pest damage. The easiest way to stop infected plants from making their way into your grow room is to not buy any infected plants. If you are tempted when someone offers you something ‘special’, treat the plant like it’s infected and keep it in a quarantine area until it’s larger and growing healthily. For your own safety.

The environment needs to be stable – This is the most important part of this regime, keeping your plants within their optimal temperature along with relative humidity depending on what stage of growth they are in. Environmental control is key to growing happy plants! To help you achieve a stable environment, an extraction fan controller will be required.

For more information on environmental control see the VPD post here.  

Use common sense – Use your noggin! Keeping a clean garden and routine of cleanliness will ultimately give you the best chance of keeping your grow free from pests and diseases. It’s the little things that matter like making sure the room your grow tent is in is clean and tidy, your plant pruning equipment is clean and sanitised, and where you are pulling air from is fresh. 

Improper watering – Under or over watering has got to be one of the leading factors in stressed/unhappy plants, especially in systems like living soil. Stressed plants are more prone to pests and disease because they are seen as weak prey or an easy target by the pests. 5% of the volume of the soil is recommended per watering. For example, a 50L pot of soil will need 2.5L, if your plants are at the start of their life it will require less. Using a Blumat moisture meter is going to be your saving grace.  

For more information on environmental control see the watering post here.  

Using beneficial insects – These should be used by all growers, and act as the first line of defence. They should be used preventatively, so if pests show up there is already an army waiting to defend the plant.

Predatory insects can be very specific, only feeding on a certain pest, but some are more generalist, feeding on a variety of pests. The generalist predators are often the best to use for prevention and specific predators for outbreaks. Here are some examples;

Fungus gnats – Use the generalist predatory mites Hypoasis miles (also known as Stratiolaelaps scimitus) at planting as a preventative. Atheta coriaria can also be used as a preventative, these are larger and will also eat springtails and other larger soil organisms that hypoasis struggle with. If you have an outbreak of fungus gnats, use a soil drench of the specific predatory nematodes Steinernema feltiae. The predatory rove beetles

Thrips – use the generalist predatory mites Amblyseius cucumeris supplied in controlled release sachets. These are hung on the plant and slowly release predators onto the crop over 4 weeks. These feed on thrips larvae, but will also eat young developing spider mites and their eggs. If you have a small outbreak, you can buy Amblyseius cucumeris in a shaker bottle and apply a lot of mature mites quickly.

Spider mites – use the generalist predatory mites Amblyseius californicus supplied in controlled release sachets. Hang these on young plants and replace every 4 weeks. These feed on spider mites and their eggs, but will also eat broad mites and thrips larvae. If you have a small outbreak of spider mites, use the pests specific Phytoseiulus persimilis predators supplied in a shaker bottle.

As a general rule, we highly advise adding hypoaspis miles to the surface of your potting mix at planting at around 100-200 mites per square meter of growing space, and use 1 slow-release predator sachet per young plant. As the plants get larger use 2 sachets per plant. The sachets are best placed on the plant out of direct light, and try to make as much contact on the plant as possible rather than leaving them dangling in the air. They love more humid conditions so try and place them under the canopy within the plant. Replace the predator sachets every 4 weeks.

Spray routine – When using beneficial insects, there is no need to spray weekly with a preventative pesticide or plant wash. Doing a weekly spray with plant growth-promoting foliar feed (such as seaweed extract, aloe vera, fulvic acid) when there are no signs of pests is a good approach that leads to overall better plant health.

If you see early signs of pests and the predators are not keeping up, using a natural plant wash containing a wetting agent/surfactant and natural essential oils as a spot spray to control the outbreak is a good approach beneficial. There is often no need to spray the whole growing area, unless you see signs of pests across the whole crop. Spot spraying helps maintain your predator populations.

If you are an organic grower using living soil, choose your pest control product carefully. Most sprays containing agents that kill insects by whatever means will have some impact on soil biology. For example, neem oil is often considered safe for organic growing but is very damaging to soil micro-organisms. If in doubt, please get in touch! We are happy to assist.

There is no magic product, just good gardening and observation. Like many things, it takes a good routine, persistence, and a bit of common sense. 

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