Worm castings are an effective way to repel white flies, aphids and spider mites and any pest that feeds on plant juices. According to recent studies, applying earthworm castings to the soil around your plants increases the production of a certain enzyme chitinase. This enzyme is a degrader of chitin, the substance that comprises the exo-skeletons of most insects. When used properly, worm casting acts as a natural insect repellant. If a bug feeds on the leaves of a plant which has absorbed the chitinase, its exoskeleton will soon begin to dissolve, and death will come quickly.
North Carolina State University researchers have dug deeper into the mechanisms behind insect resistance of plants grown in soil amended with vermicompost, and the preliminary results suggest this may provide an ecological friendly means of managing pests in vegetable crops.
Yasmin Cardoza, an entomologist and soil arthropod ecologist, along with graduate student Amos Little, found that different insect species responded differently to host plant resistance of brassica crops. They also determined that it takes as little as a 20 percent concentration of vermicompost mix in the soil to boost the resistance of host plants against caterpillar and aphid pests.
Be sure to select a quality worm casting that’s pure and not cut with compost or other raw materials. Vermisterra pure organic earthworm castings are fine, aged and readily absorbable by plants.
Resources:
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.950.1099&rep=rep1&type=pdf
https://georgia.growingamerica.com/news/2012/04/ncsu-research-explains-how-vermicompost-amended-soils-ward-crop-pests/
https://pubmed.ncbi.nlm.nih.gov/19423335/
https://www.researchgate.net/publication/317490950_Effect_of_vermicompost_and_chitin_on_the_control_of_Meloidogyne_incognita_in_greenhouse_tomato