China Mark Moths on Water Lilies: Bt Treatment Safe for Fish

Pest ID

Tiny white larvae cutting leaf pieces and gluing them over themselves = China mark moth (Nymphula nymphaeata) caterpillars.

Manual removal: Pick off affected leaves for light infestations.
Bacillus thuringiensis (Bt): Mosquito Dunks or Bt granules in the pond. Specific to Lepidoptera; safe for fish, frogs, beneficial insects.
Repeat every 7–10 days until gone.

Pond plant pests: fishpondinfo.com/plants/plantpests.htm#moths
Mosquito Dunks: fishpondinfo.com/mosquito.htm

Pond and Water Gardening: Cochineal Scale on Broadleaf Cactus: Identification and Treatment; Tiny White Worms in Self-Watering Pots: Fungus Gnat Larvae; Why Hardy Water Lilies Fail in a Cold Spring-Fed Pond; Saving Water Lilies After Ronstar Herbicide Exposure; Worm Carcasses and Smell in Pond: Wrong Advice (Pool Chlorination); Storing Water Lilies Over Winter (Michigan); Water Lily Crown Rot: Fungus, Soil pH & Leaf Removal; Water Lily Stems Clean-Cut: Animal or Human?; Tiny Red Worms in Plant Roots: Insect Larvae, Not Worms; Why Hardy Water Lilies Won't Bloom in Extreme Heat

Garden Articles

Plants