Fungus Control Using Vermicompost
by George Hahn
Note: George Hahn is president of California Vermiculture, LLC, (P.O. Box 95, Cardiff by the Sea, CA 92007, www.wormgold.com, 760-942-6086). His company manufactures Wormgold® pure worm castings and other worm casting products. This article appeared in the "Fruit Gardener", journal for the California Rare Fruit Growers, Inc., Fullerton Arboretum - CSUF, P.O. Box 6850, Fullerton, CA 92834-6850, www.crfg.org, 714-840-7694. The original article has been edited for space considerations.
Fungus control using earthworm castings sounds like a snake-oil idea since it is radically different from the traditional approaches to fungal control. However, academic research backed up by field-testing has shown that major fungus problems can be solved using earthworm castings. Castings contain over 10,000 different biological organisms. The full array of bacteria, molds, fungi, actinomycetes, chitinase, etc. creates a healthy soil food web that is capable of solving many plant problems including fungal ones
Fungus infestation is a major cause of growth problems in all plants, and they suffer because the ratio of fungi to other soil organisms gets out of balance. A particular fungus is not the problem, but the ratio and balance. If the fungus is in balance at the proper ratio in the soil, it is a key and beneficial part of the soil food web. But let the fungus get out of balance and it becomes a major problem. The fungus not only multiplies unchecked but also multiplies its food consumption. A key source of food for fungi is nitrogen. Nitrogen that is consumed by the fungi is locked up and not available for the plants. The plants then become nitrogen starved with impaired growth from the imbalanced fungus. As the fungus ratio grows out of balance, spores can be released from the soil and spread to the foliage of the plants.
Traditional Fungus Control
The traditional fungus control method involves the addition of toxic fungicides designed to kill the fungus on contact. The nitrogen from fungi killed by toxic fungicides is not readily available to plants. The killed fungi must degrade [be eaten or composted] in order for the nitrogen stored inside of them to become available for the plants.
When toxic fungi are eaten by other beneficial soil organisms, some of them are killed by the residual fungicide. Fungi-consuming organisms in the soil are one biological way to keep fungi in balance. Without beneficial fungi-consuming organisms, the soil becomes even more unbalanced.
If fungicides could be designed to kill only the fungi they would still cause soil problems because when you kill fungi, you have eliminated the food source for beneficial fungus-eating organisms. With no food source, these organisms cannot survive. Without them, the nitrogen in the remaining fungi is not released into the soil. The result is lowered soil fertility for any plants.
Regulations require that fungicides have a narrow range of effect and low toxicity. If fungicides maintained a high level of toxicity, a multitude of problems are caused that are far greater than the fungus infestation. Once a fungicide has degraded below the killing level, fungi will re-invade the treated soil. With the absence of fungus-eating protozoa and nematodes (they died when the fungicide killed their food source), fungi can multiply without restriction. As many growers and gardeners can attest from personal experience, the return of fungus problems after fungicide treatment is usually far more virulent that the initial infestation.
Fungus Control with Worm Castings
Organic gardening advocates have claimed reduced fungus problems when compost is used for many years. Similar claims have been reported by the compost industry1.. Earthworm castings are non-toxic and do not destroy any portion of the soil food web. In fact, castings contain a wide array of beneficial soil organisms so it's logical to think that applying castings, which contain organisms that consume fungi, should bring soils with fungal problems into balance. The following field tests were conducted to test this theory.
The initial field test involved a landscaping application in the San Diego, CA area. A relatively large residential hillside (30 ft x 200 ft) had been planted with Disneyland ice plant six years previously. The hillside was 75% bald with no plant growth. The existing ice plant looked very sickly and had not given any new growth in two years. Many attempts at planting new ice plant resulted in none surviving. Other plants had been planted with the same negative results of no growth. Soil tests taken by the landscaper had shown an imbalanced concentration of phytophtora. Several fungicide treatments had been applied with no positive net results.
The earthworm castings growth study by Ohio State2. indicated an optimum ratio of worm castings at 10-20%. This has been determined to be equal to a ½ - 1 inch layer of worm castings. This was used as the guideline and a one (1) inch layer of worm castings was applied to the entire hillside. The last fungicide treatment had been carried out over 60 days previously. It was felt that the toxicity concentration would not be injurious to the biology in the worm castings. It was determined to wait 30 days before installing any new plantings or any testing. Before the end of the 30 days, all of the existing ice plant was showing vigorous new growth. The hillside was replanted with new ice plant, which quickly took root and flourished. The soil was tested for the phytophthora level and was found to be within guidelines. This hillside was still lush with ice plant growth after two years.
A grove of lemon trees was then tested. This grove had been found to have a heavy concentration of phytophtora as well. The trees were each showing bark weepage and unhealthy foliage. Thirty trees were given a one-inch application. Within four weeks the trees showed significant health improvement.
Academic Research Confirmation: The initial literature search had not shown research using earthworm castings to solve fungus problems. After field tests had proven successful a more diligent literature research was conducted. Four research articles were found where fungus control using worm castings was carried out under close academic protocol. Phytophthora nicotiniae3., fusarium oxysporum4., sclerotinia sclerotium5., and sclerotum cepivorum6. were able to be controlled with the use of earthworm castings.
Fungus control in inoculated soil tests was not achieved when too little of the earthworm castings were used. The 20% level (one inch layer) that the field tests showed effective was confirmed as an effective concentration in the research articles.
Improved Application and Further Tests: Several rose applications with definite fungus problems were tested with the same 20% application and showed clear improvement in less than 30 days.
The field tests showed a problem with dry-out of the earthworm castings and a hydrophobic reaction by the dry castings. Each earthworm casting is coated by the worm when excreted. Some have described this as a mucous coating. The castings hold together similar to cottage cheese when above about a 40% moisture level. Below this level the coating on each casting makes the castings react to water similar to dry flour. Water will bead on top and will roll off a sloped layer. Water needs to penetrate the castings and flow into the soil. Covering the layer of castings with a layer of compost or mulch solves the hydrophobic reaction of the castings. The porous nature of the compost quickly captures moisture like a sponge and allows the water to penetrate the castings.
Field-testing for fungus control has shown an increased effectiveness when the castings are kept moist. John Buckerfield's vineyard testing6. for growth showed a marked improvement in growth effectiveness when a mulch layer was added over the earthworm castings. Buckerfield showed that the mulch was not responsible for improved growth without the earthworm castings. This author feels strongly that the mulch layer is needed to keep the moisture level up in the castings to provide full effectiveness. Rapid penetration of the mulch/castings layer is evident for tree applications. The penetration of new feeder roots indicates that the tree is receiving needed nutritional benefits from the material in this layer.
The observation of root penetration can be seen by a simple test with a potato. Place a thumbnail size of earthworm castings at the bottom of a clear container of topsoil. Circle the spot of earthworm castings on the outside of the container. Plant a potato in the container and observe the feeder roots. When the first root tendril touches the circle of castings an amazing thing happens. Within a few days, the small feeder roots around the whole potato have changed direction to seek out the circle of castings. Magically the circle will become the feeding center for the potato as the small quantity is totally enveloped by the feeder roots.
Don't Kill the Life Treat the earthworm castings as filled with the biological life needed for healthy soil. If the soil has been saturated with a fungicide or pesticide, death will come to the biology of the castings. Cover the layer of mulch/castings with a layer of plastic before applying fungicide or pesticide treatment to the leaves.
Apply the one-inch layer of castings with a layer of mulch in the first year. In subsequent years the treatment can be a one half inch layer covered in mulch. The fungus ratio will be held in-balance providing a healthy soil-food web for your trees giving improved growth and eliminating problems.
References: Compost Suppresses Disease in the Lab and on the Fields by Jerome Goldstein, BioCycle November 1998 pages 62-64
Comparing Vermicomposts and Composts by Scott Subler, Clive Edwards, & James Metzger, BioCycle July 1998 pages 63-66
Suppressive Effect of a Commercial Earthworm Compost on some Root Infecting Pathogens of Cabbage and Tomato by M. M. Szczech, W. Rondomanski, M.W. Brzeski, U. Smolinska and J.F. Kotowski, Biological Agriculture and Horticulture, 1993 Vol. 10 pages 47-52
Suppressiveness of Fusarium against Fusarium Wilt of Tomato by M. M. Szczech, Journal of Phytopathology, 1999 Vol. 147 pages 155-161
Control of Sclerotium cepivorum by the Use of Vermicompost, solarization, Trichoderma harzanium, and Bacillus subtilis by JCR Pereira, G.M. Chaves, L. Zambolim, K Matsuoka, R.S. Acuna, & FXRD Vale, Summa Phytopathologica, 1996 Vol. 22 no. 3-4 pages 228-234
Worm-worked waste boosts grape yields. Prospects for vermicompost use in vineyards. By John Buckerfield & Katie Webster, Wine Industry Journal, Feb 1998 Vol. 13 No. 1, Pages 73-76
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