Tiny Green Worms on Water Plants: China Mark Moths

Tiny green worms/parasites on pond plants, lily pads dying. Fish fine. Need plants for fish. Asked ID and treatment.

Also called "sandwich worms."
Check lily stems below water: two dime-sized leaf pieces "sandwiched" with worm inside.
Eat leaves, not roots.

Dipel Dust (Bacillus thuringiensis): Powder, not insecticide. Gives worms fatal stomach ache. Only affects caterpillars. Safe for fish, frogs, beneficials.
Apply: Dust on leaves.
Available at home centers.

Asked if owner has 'Tina' water lily (dark purple/blue tropical).

Bt products are the gold standard for caterpillar control in ponds.

Pond and Water Gardening: Plants Around a Chlorinated Pool: Salt Is the Real Enemy; Controlling Caterpillars on Miniature Roses; Deionized Water for Carnivorous Plants: Testing and Validation; Do You Need to Let Tap Water Sit Before Watering Plants?; Persistent Green Algae in Large Koi Pond: Filter Maturity and Maintenance; How Often to Water Your Garden: A Climate-Based Guide; Algae Control Without Plants: Dealing with a Plant‑Eating Groundhog; Poor Plant Growth in a Hard‑Water Well Pond: Fertilizer, Light, and Nutrient Testing; Green Algae in a Small Frog Pond: Algaecide, Barley Straw, Floaters; Best Aquatic Plants for Water Gardens: Marginals, Lilies, and Edge Plantings

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