Got Lily Leaf Beetle?
Also known as Scarlet Lily Beetle, Lilioceris lilii, this pest only eats Liliaceae. Infestations have increased explosively in Maine in the past few years. We’ve heard of several techniques that may be worth your time.
From professional gardeners Downeast: When you see the mother (she’s red), she probably has already laid her eggs, usually on the undersides of the leaves. Pick her off and, if you can, crush or drown her in soapy water.
Put on a pair of soft cotton gloves and spray them heavily with diluted neem oil solution. Starting at the base of the lily stalk, run your gloved hand up under the leaves to the top of the stalk. This will coat the leaves with neem and will kill any eggs that happen to be there.
Spraying the neem oil is not enough—you need to get the stalk and the undersides of the leaves coated by using the soaked glove. Neem oil will not kill the mother. Using this treatment along with daily checks, they are seeing fewer beetles.
A vigilant customer uses one part liquid Dr. Bronner’s Peppermint soap to 8 parts water. “It works [even] if I have to spray many times a summer. I have my lilies and I don’t worry about them. I never go outside without my spray bottle.” She also reports that it “contact kills” ticks, carpenter ants, slugs and the parent red lily beetle, which the proponents of neem oil admit that it does not do.