Hello, my boxwood hedge is infected with leafminer. Would Safer insect soaps be effective at this time? Would lawn care companies have commercial products that would be more effective? Thank you
Hello, thank you for contacting the Toronto Master Gardeners. I am sorry to hear that you have discovered a Leaf miner infestation on your Boxwood. To answer your question, no I do not believe that applying insecticidal sop will be effective at this time. Insecticidal soap is effective against soft bodied insects such as aphids, spider mites, thrips, whitefly, and mealybugs. It is also effective against Boxwood psyllid, another common boxwood pest.
Natural controls of this pest would include encouraging natural predators such as green lacewings and spiders as well as maintaining plant vigor through proper fertilization and watering since healthy plants are more tolerant of insect damage. Environmental controls of Boxwood miner would include pruning away and discarding in the garbage all infected plant material, carefully removing any leaves that may have fallen to the ground. Although it is too late to do so now, a way to interrupt the lifecycle of these pests is to prune out new growth in the spring preventing females from laying their eggs. Also helpful in the spring is to hang insect sticky traps nearby. These trap the adult gnat like flies as they emerge from their leaf cocoon. I am enclosing a link to a website describing the Boxwood leaf miner, please note however this site suggests pesticides (insecticides or herbicides) that are banned from cosmetic use in Ontario. I hope this helps