Last week I was a guest on a gardening talk show and a listener asked about controlling tomato hornworms. The hosts were slightly incredulous when I mentioned that controlling tomato hornworms and all other pests and diseases not usually associated with soil quality, are directly related to the quality of your soil and a rich biodiversity of microbial life in the soil. The hosts asked, “How could applying John & Bob’s products impact the presence or absence of tomato hornworms?”
This is a fascinating question, unfortunately the answers are not simple and not completely understood by current science. An important factor is that 75% of all insect pests spend part of their life cycle in the soil and many of their natural enemies occur there as well (this happens to be the case with the tomato hornworm)as long as the soil is rich with complex soil life. Another factor is that most pests lack a liver and can’t digest high concentrations of amino acids (which very healthy plants possess), this is one way the plant is made to be an unattractive nutrient source by healthy soil. Another plant/soil mechanism representative of a whole range of mysterious interactions involves chitin, which helps form the cell walls of bacteria and fungi, and is a main component of the exoskeleton of insects and worms. Chitonase is the naturally occurring enzyme which breaks down Chitin to create Chitosan, a natural pesticide and fungicide. Get this, when a plant detects chitin (part of the structural makeup of bad insects and worms), the plant knows it is being attacked and it will start making chitinase (given proper soil properties and plant health) to break down chitin to create Chitosan, which is a pesticide. In this way, many plants produce their own “insecticide” and “fungicide”, relying on soil life as its source to access the necessary enzymes. This is not meant to be a comprehensive description of all the natural plant/soil mechanisms to prevent/defeat pests and disease. But, I hope it can open up minds to understand the tremendous complexity and capabilities of the natural world. Soil health and life is really the foundation of all the natural mechanisms, many of which we understand only partially or not at all. Tomato hornworms beware, we are beginning to understand the power of rich soil full of complex life.