We will be increasing our prices on 16 May 2021. Buy your products now before the price increase.
Product List

Natural Pest and Disease Management

I was asked if we have a natural pesticide for the use in vegetable gardens? The answer to that question is both yes and no. Yes because you can use products to boost plants health and natural defence systems and no because I do not use  insecticides, bactericides or fungicides.

My approach to pest and disease management is to use a preventative approach rather than a curative approach.

The method I prefer to use is has two approaches:

  1. Boost a plants health which promotes its natural pest and disease-fighting ability.
  2. Use products which build up healthy colonies of microbes that predate on pest and disease-causing organisms.

Black Spot on Roses, Mealybug on Orchids

A - Healthy roots, healthy plants.

Plant health starts with the roots. If your plant does not have sufficient roots to absorb nutrients and water it will suffer from nutrient and moisture stress. This state will affect a plants ability to resist pest and disease infestation and plant growth processes slow down when there is moisture and nutrient stress, i.e. growth/photosynthesis, etc.

Some strategies you can employ to improve this are:

  • Check to see if your growing substrate holds sufficient water. A good substrate should hold sufficient water for two or three days and on the other hand if your substrate holds too much water, it could cause your roots to rot. Both conditions will affect your plants ability to develop good root systems and in turn affect nutrient and moisture absorption.  
  • Check that your substrate is not full of salt from incorrect fertiliser use. Dyna Gro Nutrient Solutions used at the recommended dilution rates result in very low salt levels.
  • If your plant does not have sufficient roots use BioPower Seaweed Flake and Organic Root-Gro as a pot drench once a month. The can be used individual or mixed together.


B - EM1 garden, helps develop populations ‘good’ microorganisms.

EM1 Garden a naturally brewed product helps build and establish beneficial populations of beneficial microorganisms soil//potting mix and on leaf surfaces.

If the soil/potting mix contains abundant populations of beneficial microorganisms, the natural fertility of the soil or potting mix will be improved. This, in turn, results in improved root and plant growth as well as improving a plants ability to resist pest and disease infestations.

When you apply EM1 Garden to the foliage, populations of beneficial microorganisms establish themselves on the leaf surfaces. In turn, these beneficial microorganisms can predate on most pests and diseases infestations.

I have managed aphid, blackspot and powdery mildew successfully using a weekly spray and soil drench using a dilution rate 1:1000. If you have high disease pressure you could try using a dilution of 1:100. EM1 may not eliminate the infestation but should reduce it to an acceptable level. You can read more about EM1 at this page: www.bioleaf.co.nz/product/em1-microbial-inoculant.

EM1 is also incredibly good for the soil. All you need to do is apply 10 ml of EM1 to 10 litres of water (watering can) and pour it liberally on to the soil (drench). A weekly application works best.


C - Seaweed Foliar Spray, for plant health and vibrant growth.

Another option you could look at is using a seaweed foliar spray once or twice a month as preventative for leaf borne pest and disease attack.

The foliar application of seaweed brings many benefits to plants such, helping establish colonies of microorganisms on the plant, supporting chlorophyll production, deepen the colour of foliage and flowers and help grow strong and healthy plants.

Seaweed has many benefits for plants. Researchers have observed for plant foliage that has been sprayed regularly with seaweed, that insects seem to have an agitated state and do not settle well on plants. It is believed that this affects their ability to reproduce.

Orchardists in California who have sprayed their trees with seaweed several times a year have noticed that year on year the pest and disease infestation reduces in intensity.

Please note seaweed is not a fertiliser. We take vitamins to supplement our diet and improve our health, seaweed does similar for plants. If you are using seaweed on your pot plants, you still need to feed them with a good quality fertiliser.


D - Regular application of a refined mineral oil

The regular application of a refined mineral oil like Organic EnSpray 99 Spraying Oil which has both insecticidal and fungicidal properties can help with controlling thrips, mites, aphids, scale, powdery mildew and botrytis. It is important to do follow up sprays to kill newly hatched insects. Organic EnSpray99  is registered for organic use and has a nil withholding period.

EnSpray 99 is also available as a handy ready to use spray unit. This is useful for doing spot sprays to kill insects


E - Use a copper based spray for the control of fungal infestations.

FreeFlo Copper can be used to control a wide range of fungal and bacterial diseases on fruit, vegetables and ornamental plants. FreeFlo Copper is registered for organic use and has a nil withholding period


F - Silica to boost cellular strength plus a few more benefits.

Another option to look at is using a silica-based foliar spray. Silica strengthens the cells and makes it more difficult for pests and disease to penetrate the cell walls. Some tunnel growers have used silica-based foliar sprays as an effective control for powdery mildew infestations. You can read more about silica at this page: https://www.bioleaf.co.nz/dyna-gro/pro-tekt-liquid-plant-food 

Please note Pro-TeKt is not registered in NZ for pest and disease management and it is a mineral supplement.


G - Wrapping it all up into a process

My recommendation would be to combine the silica and EM1 and spray/drench your plants weekly. Make sure you drench the underside of the leaves. Once a month say the first weekend include the seaweed solution. Alternatively, you could include Pro TeKt with your fertiliser application. Always add the Pro-Tekt to the water first, stir and then add your fertiliser.

When you use this approach the results are not instantaneous it takes time. Done properly, month on month, you will see improvements and the incidence of pest and disease infestation should diminish over time.

Another intervention is to mix Free Flo Copper, BioPower and EnSpray 99: May be used together to control fungal disease and pest infestation. It is important to use the correct mixing order:

Scientists have observed if the Brix levels (sugar in the plant) are raised significantly pest infestation is much lower. High Brix levels are an indication that plants are growing well and are healthy. Scientists speculate that for plants with elevated Brix levels, insects find the sap is ‘too sweet’ and move off to find another host plant.

Remember this only a guideline and the best advice that I can give you is to use this as a starting point and adjust accordingly to suit your cultural practices.

I hope this helps and feel free to contact me with your questions.

Return to articles page