Earthworm castings have been used for centuries to increase the quality of soil and to improve the overall health of plants growing in that soil. Aristotle, the philosopher, called them "The Plows of the Earth," Charles Darwin spent a great deal of time looking at and studying these amazing creatures. The net result of all this fuss about wigglers was that they became revered as the most helpful and beneficial organisms in any garden or on any farm or nursery where plants are grown directly in the ground. Today, many of us don't have the space or the inclination to make an attempt at worm or "vermi" composting so we go directly for the castings, which are sold at garden centers and nurseries all over the country. Worm castings have hit the mainstream because gardeners are finding out that they do so much more than just improve their soils.

Worm casts are digested organic matter that has been run through the gut of the earthworm. They are one of the most stable sources of organic matter for the garden and the biology they support is unlike that of any regular commercial or home made compost. Earthworms impart into their casts an incredible diversity of hygienic microorganisms that work to competitively exclude disease-causing organisms as well as a number of destructive pests such as root knot and root lesion nematodes. Worm castings have recently been discovered to fight other pests on plant surfaces also through an ingenious little enzyme known as chitinase.

Chitinase is a degrading enzyme that eats the material chitin. Here is the fun part.pest insects are made of chitin. Chitinase is formed by several types of microorganisms that are found in the gut of the humble earthworm. Chitinase producing organisms are theorized to be taken up by plant roots in the water they utilize and are then moved throughout the plant via vascular tissue. This translocation results in chitinase being distributed into the leaves and other parts of the plant. When a pest insect such as an aphid, mealybug, whitefly, or any other plant-feeding insect begins taking juices from a plant with chitinase in it they find out the hard way what chitin degrading means. The chitinase works to dissolve the insect's stomach lining thus disabling the pest. It dies from the fact that its insides are being slowly dissolved. There can be no more effective way to control pest insects on plant that this method because insect pests cannot change what material makes up their bodies. And it is very difficult in nature to develop resistance to things that eat you.

Earthworm castings also have the added benefit of being loaded with other beneficial, hygienic microorganisms that will help your plants fight such regular maladies as powdery mildew, rust, black spot, and a number of other fungal pathogens through competitive exclusion. Competitive exclusion is the process by which one species dominates and eventually excluded another from surviving. With worm castings you get so many beneficial organisms that the pathogens do not stand a chance of survival.

When applying worm castings to the garden, it should be known that the best place for them is where your plants do the majority of their feeding, the dripline. Worm casts should be applied in a ring of about three-quarters to one inch in thickness around the dripline of your plants for maximum insect and disease repellency. This ring should be in the form of a band of between six inches to two feet wide depending on whether you're using it on smaller shrubs or trees. A layer of organic compost over the top of the casts will help to keep them moist and protect them from the sun depleting their biology, which is sensitive to the rays of the sun.

So the next time you are cursing your poor soil quality, raving at your pest infestations, or lamenting the outbreaks of fungal diseases in your garden, reach for some earthworm castings. With a little patience you'll see the amazing effect of the lowly earthworm on your precious gardening spaces.