There is a lot of scientific research on the uses and effects of earthworm composting. A great resource for those wanting to investigate details is Vermiculture Technology: Earthworms, Organic Wastes, and Environmental Management edited by Clive A Edwards, Norman Q. Arancon, and Rhonda Sherman. Here are some highlights:
About choosing the type of worm for composting, according to the “Biology and Ecology of Earthworm Species used for Worm Composting” by Jorge Dominguez and Clive Edwards, Eisenia Fetida ” are most commonly used in vermicomposting and vermiculture mainly because they are ubiquitous with a world wide distribution and colonize organic substrates naturally, their life cycles are short, they have a wide temperature- and moisture-tolerance range, and they are resilient earthworms that can be readily handled”.
Benefits of using vermicompost for growing plants is discussed in “Quality Criteria for Vermicomposts” by Edwards, Arancon, and Scott Subler. They state that “because the material passes through the earthworm gut at least once, a significant but not fully understood transformation takes place, whereby the resulting earthworm castings are extremely abundant in microbial activity and plant growth regulators and fortified with pest-repellency attributes as well. “
In an article illustrating increases in plant growth of plants grown in red wiggler compost, “Vermicomposts as Growth Media in Greenhouse Crop Production” by Arancon, Edwards, Katie A Webster, and John C. Buckerfield, they state, “Improvements in the growth and development of greenhouse crops after addition of vermicomposts, result in much greater economic returns to the grower, due to faster germination rates, earlier flowering, larger yields and better quality crops”. Crops studied included peas, lettuces, wheat, cabbages, tomatoes, peppers, raspberries, radishes, chrysanthemums, and petunias.
About studies of insect repellency of plants grown in vermicompost, there is an article in the book by Edwards, Ahmed M. Askar, Marcus A. Vasco-Bennet, and Arancon called “Suppression of Arthropod Pests and Plant Parasitic Nematodes by Vermicomposts and Aqueous Extracts from Vermicomposts”. The authors state: “Our results demonstrate that substitution of solid vermicomposts into (growing mix) MM360 had considerable influence on the intensity of attacks by aphids, mealybugs, spider mites, cucumber beetles, and tobacco hornworms”.
It is encouraging to note that improved crop performance is often optimized by using a soil mix containing 20% vermicompost with your regular potting mix or garden soil! So harvest your red wiggler castings and add them to your garden as is or mix with water to make a fertilizing tea!