Monday, January 22, 2018

Using Beneficial Fungi to Improve Garden Health

Our local growing conditions are typically temperate and wet - brilliant for growing, but also perfect for pests, disease, and fungus. Blah. Between my personal desire to minimise chemicals in the garden, safety for our pets, and trying to keep things bee-friendly it is a constant struggle to maintain a healthy garden.  Biocontrol agents are beneficial organisms that you can apply or introduce to your garden/soil to help reduce the prevalence or impact of undesirable pests and diseases. Under the broad umbrella, biocontrol agents include plants (competitors), beneficial insects (competitors, predators, and parasites), and pathogens (bacteria, fungus, and viruses). 

Biocontrol for pet insects and animals is a familiar concept for many gardeners, but did you know that you can also use beneficial pathogens to fight undesirable pathogens?  In my fight against the omnipresent spectre of fungal disease here in the NZ garden, I've started actively treating my soil with beneficial fungi. Yes, fighting fungus with fungus! You might see these marketed by specific variety or variety grouping, or as mixed content inoculants or biofungicides. I find the latter kind of funny when the content actually includes fungi, but hey! In addition to helpful varieties of fungi, biocontrol mixtures may also include beneficial microbes and bacteria. Healthy soil is filled with organisms that we don't see or readily appreciate, and these inoculants and biofungicides are meant to restore or augment natural populations of the garden good guys. 

This type of biocontrol is most effective as a prevention before you start to see signs of ill-health in your plants. The agents usually work in a symbiotic manner with the host plants in the garden soil and plant root systems: they colonise the treated soil and compete with pathogens for nutrients and space, attack pathogens parasitically, create compounds which alter the soil environment to make it less hospitable to pathogens (antibiosis), and/or enhance the pathogen resistance, nutrient uptake, and general health of host plants whose roots they colonise. Sounds good, right?  

Even better news is that most of the biocontrol products marketed to home gardeners are easy to apply, safe (take care when applying, follow product instructions), and comply with organic garden principals.  Trichoderma and Mycorrhizae fungi are two of the common beneficial fungi families on the current market for home gardeners, whether separately or as part of a mixed content product.

If you're looking for a product to try, here are a few tips:
  • Shop for your intended use. Are you treating bare soil? Seeds/seedlings? Established plants?  Trying to recover from or prevent a specific problem?  Some products may be better suited to your specific purposes. 
  • If suitable for your intended use, consider buying a product with a variety grouping (e.g. multiple strains of Trichoderma) or mixed content product to consolidate your treatment cycles.
  • Research reputable local suppliers 
  • Look for products with listed/guaranteed content.
  • Look for organically certified products.
  • Look for stable products with a decent shelf-life.

I'm a new convert to using applied biofungicides. After last year's unusually wet weather, even some of the very well established plants in our very old heritage home were under serious stress. Fungal disease was taking hold, with blight, dieback, root rot, and just general soggy soil rot. Eek!  My usual methods were no match for what nature was dishing out. I needed a new tool in the fight for garden health. I ruthlessly removed lost causes and cut out the worst affected parts of ailing plants we hoped to save. I didn't want to drench or spray with chemical fungicide, if possible, but in one very severe case for a sickly mature pseudopanax (pictured below) we cut and then applied a careful localised dose of fungicide. Two of the raised edible garden beds were also fully stripped and solarised. The next step was to try fighting to prevent further fungus with fungus.

The biofungicide products I'm currently using came as easy-to-mix powders that I can mix and apply from my watering can (how easy is that?). It goes on as an initial inoculation soil drench and then periodically thereafter for a refresh. I also applied it after the waiting period post-fungicide to my ailing pseudopanax (so far so good!) and applied both the biofungicide and a microbe/bacteria innoculant (liquid concentrate) to my solarised beds to restore beneficial content to the sterile soil.  Since my fungi are being used primarily as a prevention and I'm not poking around the roots with a microscope, it's hard to say with absolute certainty that it is helping, but since starting use things have been quite healthy in the root department and growth has flourished. Our established plants bounced back better than usual from winter, which is extra exceptional considering we transitioned rapidly from sodden to drought creating a high stress scenario. It hasn't helped the arrival of foliage fungus with our recent shift to wet humid weather, but hopefully the plants are a little stronger to help fend it off.  I intend to keep using it, and will start our garden at the new house with well inoculated soil.

Have you tried beneficial fungus biocontrols in your garden? Have any helpful tips? Success stories? Tales of woe?  Leave us a comment. :) We'd love to hear your stories and ideas. If you have your own blog/website or a favourite read you'd like to share you can leave a live link in the comments using the following format as a guide: <a href="">text you want shown for your link</a>

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