The Micro-World

One of the worst things for the landscape and garden that mankind has ever made is fungicides. They indiscriminately kill microscopic living organisms and leave your soil and plants defenseless. Many harmful plant and soil problems are kept at bay by sufficient numbers of beneficial microorganisms. I have heard it equated to the microflora in our bodies. We all have harmful organisms running around in there that are kept in check by greater numbers of good organisms or Probiotics. When we are given antibiotics in the wrong amounts, large numbers of the good microflora are killed, and the bad news microscopic guys (like C-Diff) get to come out and play. We end up fighting these difficult-to-kill, antibiotic-resistant infections. The soil and plants are no different. When you apply a bunch of chemical fungicides, you get similar results. Good microbes are suppressed that not only fight bad microbes but also play a huge role in breaking down organic matter and plant nutrient absorption.

Biofungicides

So, what do you do? Biofungicides use naturally occurring beneficial bacteria and fungi to prevent and suppress harmful plant pathogens. They are primarily used to keep away common diseases such as powdery mildew, downy mildew, botrytis (gray mold), root rot, damping-off, and various leaf spots as well as Soil/Root Diseases: Root rot, damping-off, fusarium, and phytophthora.

I don’t love the term, “biofungicide”, it is somewhat of a misnomer. While it implies a direct equivalent to a chemical fungicide that kills pathogens on contact, most biofungicides are actually living microorganisms (like beneficial bacteria or fungi) or natural extracts that protect plants through prevention and natural defenses.

The term can be misleading because of the way these biological products actually function:

They Rarely “Kill” on Contact: Unlike synthetic chemicals, biofungicides rarely annihilate pathogens upon application. Instead, they outcompete harmful fungi for space and nutrients, secrete natural antibiotics, or physically block them from infecting the root system.
They Act as Plant Vaccines: Many biofungicides do not attack the pathogen directly at all. Instead, they trigger a plant’s natural immune system, causing it to build up defenses before an infection takes hold (Induced Systemic Resistance).
They Target a Broader Range: They are often effective against a spectrum of both fungal and bacterial diseases.

Because of these differences, experts often consider “biological control agents” or “plant protectants” to be more accurate descriptions than “fungicide.”

What To Use

There are many crop protection products that utilize beneficial living microbes (like Bacillus and Trichoderma). No single biocontrol works best across every case, but Trichoderma harzianum has some of the strongest evidence. Bacillus amyloliquefaciens is also promising, forming protective biofilms on roots. Trichoderma virens can work even better when combined with Trichoderma harzianum, and that combo is often used on woody ornamentals. Timing matters. These biologics work best as preventatives or early interventions. Once Verticillium is established in a tree, results are limited. For nurseries and woody ornamentals, I’d prioritize Trichoderma harzianum plus T. virens, and Bacillus amyloliquefaciens used preventatively.

We frequently recommend : Monterey Complete Disease Control

It works as a biological fungicide and bactericide that uses a beneficial, naturally occurring bacterium, Bacillus amyloliquefaciens (Strain D747), to prevent and suppress plant diseases. It protects plants in two main ways:

As a Foliar Spray: When sprayed on fruits, leaves, and flowers, the beneficial bacteria multiply on the surface and outcompete disease-causing fungal spores and bacteria for space and nutrients.
As a Soil Drench: When applied to the soil, the bacteria colonize the plant’s root hairs. This creates a protective barrier that physically prevents harmful root rots and wilts from establishing themselves.

This preventative approach is OMRI Listed for organic gardening and is safe to use on vegetables, ornamentals, and fruit trees up to the day of harvest. It is highly effective against common issues like powdery mildew, anthracnose, and black spot.

It is available in a Concentrate that you can mix yourself, a Ready-to-Use premixed bottle, or a hose-end Ready-to-Spray that mixes as it sprays.

We have these products in our store at Farmers Nursery in Leander or they can be ordered online using the links below.