Hi Lucy,
What you are likely seeing is the Scarlet Lily Beetle (Lilioceris lilii). While attractive at first glace, scarlet lily beetles are horribly destructive. They first appeared in New York State around 2012 after being accidentally imported to Canada in the late 1940s.

Scarlet lily beetles and their larvae, can defoliate Asiatic, Oriental, Martagon and similar lily species, causing strain to the plant and adversely affecting its appearance. At least they don’t bother daylilies.

Here are hopefully a few effective organic methods to manage scarlet lily beetles.

Identification and Timing

• Appearance: Adults are 6–8 mm long, bright red with black heads, legs, and undersides. They drop and flip upside down when disturbed, blending into soil. Larvae are orange-brown, slug-like, and cover themselves with black excrement, feeding voraciously on leaf undersides.
• Lifecycle: Adults emerge in early spring (April–May), lay 250–450 red eggs in rows on leaf undersides, and larvae hatch in 4–8 days, feeding for 16–24 days before pupating in soil. A second generation may appear in mid-summer. They overwinter as adults in soil or debris.

Organic Control Methods

Hand-Picking:

• Tools: An old pickle or jam jar filled with warm soapy water and a medium sized artist’s paint brush.
• How: Check plants early morning when beetles are sluggish. When you spot a beetle or larvae on a lily leaf, hold the jar of soapy water beneath the leaf and brush the beetle into the water. Works well for Japanese Beetles infestations as well.
• Frequency: Every 2–3 days, focusing on undersides and leaf-stem junctions.

Egg and Larvae Removal:

• How: Inspect leaf undersides for red egg rows and larvae. Remove with a brush in a similar manner. Don’t touch the larvae, their excrement coating is gross!
• Frequency: Twice weekly during June–July when eggs and larvae peak.

Traps and Barriers:

• Grapefruit Rinds: Place rinds near lilies to attract beetles, check daily, and dispose of in warm soapy water. This could double as a slug control.
• Diatomaceous Earth (DE): Sprinkle food-grade DE around lily bases (1-inch band). It dehydrates beetles and larvae on contact. Reapply after rain.

Encourage Natural Predators:

• How: Attract birds (e.g., via a birdbath or feeder), frogs, or ground beetles by avoiding pesticides. Parasitoid wasps (e.g., Tetrastichus setifer) are being introduced in some areas and may eventually reach NY, targeting beetle larvae.

Neem Oil (I don’t use it, but if you’re short on time):

• How: Apply neem oil (mixed with water and a drop of soap) every 5–7 days, covering all leaf surfaces, especially undersides. Continue through the summer.
• Caution: Use early morning or late evening to avoid harming pollinators. Test on a small area first.
• Does it work?: Some report limited success.

Additional Tips

• Sanitation: Remove plant debris and loosen the top 2–3 inches of soil around lilies after the first frost (October) to disrupt overwintering adults.
• Resistant Varieties: If damage persists, consider lilies like ‘Defender Pink’ or species like Lilium henryi ‘Madame Butterfly’, which show some resistance. Avoid replacing all lilies—your garden’s diversity is a strength.
• Avoid Chemicals: Insecticides (e.g., permethrin) work but could also harm birds and beneficial insects.

Reality Check

Hand-picking is labor-intensive but effective for a small garden. Some gardeners report cyclical declines after years of diligence, suggesting persistence pays off. If beetles overwhelm despite efforts, reducing lily numbers or switching to resistant types might be pragmatic, though it’s a last resort given their beauty.