The adult lily beetle is 6 to 9 mm (1/4 to 3/8 inch) long, with longish legs and antennae. Its elytra (harder forewings) are bright scarlet and shiny. Its underside, legs, eyes, antennae and head are all black. It has big eyes for a beetle this size, a narrow thorax, and a wide abdomen.
The adults overwinter in the soil and emerge in early spring to mate. Females lay up to 450 eggs a year – normally in batches of 12 on the underside of leaves. You’ll recognize the eggs (reddish orange to brown) as they’re laid under the leaf in irregular lines along the middle of the leaf. They hatch in 1-2 weeks.
These larva eat voraciously for 24 days and you’ll find them mostly under the leaf or right at the spot where the leaf meets the stem (hiding there) After 24 days, they drop off the plant dig themselves into the soil to pupate. After 20 days, they emerge as adults to continue eating and breeding.
Control of This Pest
Handpicking is one option for sure. Another closely related is to get a small bucket of hot, soapy water and put it under the leaves where the beetle are feeding. Then shake the leaves.
You see, this beetle drops off the leaf at the first sign of a predator (that’s you) so if you put the bucket under the beetle, it will take a swim.
Second, Neem (Amazon link) is supposed to kill this insect. At the very least it may repel it.
Third: Spinosad (Amazon link) is a spray produced from soil bacteria that’s also supposed to kill red lily beetles.
Caution: Pesticide registrations vary from province to province and state to state. You MUST read the label to see if the product is registered for this pest in your area. And you must follow label directions for application.