Nematodes are microscopic roundworms. Earthworms are not harmed. Challenges to date have been in rearing and shipping parasitic nematodes, as well as improving application methods. Current research focuses on matching parasitic nematodes with environmental conditions, soil temperature and the pest to be controlled. Others remain active down to 50 degrees Fahrenheit and are more viable in cooler climates.
Nematodes are generally mixed in a bucket of water and applied to soil with a sprinkling can.
Work quickly, though. Nematodes can drown if left in water for longer than an hour. Lacewings show promise in controlling azalea lacebug, one of the most ubiquitous and annoying pests of rhododendron, azalea and Pieris . Buy from companies that ship eggs or larvae rather than adults, since only the larval stage is predatory. Multiple applications are recommended, especially if the lacewings haven't reduced pest populations in five to seven days, or to control successive generations.