University researchers are conducting studies using the earthworm compost Worm Power, which has been shown to be effective in suppressing the common crop disease Pythium aphanidermatum (known as “damping off”) in cucumber seedlings.
Allison Jack, PhD candidate in the Department of Plant Pathology and Plant-Microbe Biology at Cornell, has conducted disease suppression experiments in which cucumber seeds are sown in sterile sand or sterile sand mixed with 40% vermicomposted dairy manure (Worm Power). All of the seeds are then inoculated with an equal quantity of the pathogen Pythium aphanidermatum. Consistent light, moisture and temperature were maintained in a growth chamber. The results were startling: The cucumber seedlings sown in the sterile sand died at a much higher rate than the seedlings sown in the sand-vermicompost blend. “When we control all these variables, you see a very big difference in disease symptoms and plant survival,” Jack said.
Since sterilized vermicompost offers no protection from the pathogen, Jack theorizes that “living soil” is the secret. When sown in sand, germinating seeds release chemical cues that the pathogen uses to find and infect the plant. Microbes in the vermicompost colonize a seed almost as soon as it’s planted. These microbes alter the chemical signals released from the seed, which keeps the pathogen from finding the seed, thus preventing infection from occurring. “So, it’s not just the vermicompost itself,” Jack said, “It’s this very intimate and rapid interaction between the vermicompost, the seed and the pathogen.”