Dill Worms

Parasitic wasps lay eggs on or inside swallowtail and other caterpillar larvae, turning them into mummies or clusters of silk cocoons -- leave those cats alone if you want free control. Birds and assassin bugs pick off larger larvae on outer umbels. If you see tiny wasps hovering near dill flowers, do not fog the row with soap; you are killing the help. Diverse flowering plants nearby feed adult parasitoids when dill is still small.

Inspect dill, fennel, and parsley from the moment umbels form -- butterflies lay round eggs on leaf tips you can crush with a finger. Check undersides at dawn when adults are less active. Decide if you want zero holes for market herbs or shared butterflies for seed saving; mixed goals confuse spraying. If you grow for seed, tolerate some feeding on sacrificial plants. Flag rows that showed heavy larvae last year and scout those first next spring.

Plant extra dill or fennel along a fence as a trap crop so egg layers find it before your kitchen row. Rotate locations so pupae in soil do not meet the same umbel next year in tiny gardens; big fields move blocks farther. Avoid ultra-lush nitrogen that pushes soft growth every two weeks; it makes damage look worse and attracts more egg layers. Interplant with tomatoes or other non-hosts for visual diversity, not magic repellence -- diversity mainly helps predators move in.

Hand-pick larvae in early instars when they sit on top of leaves and drop into soapy water. Floating row covers over seedling dill block adults until you remove covers for pollination or harvest -- bury edges so moths cannot crawl under. For small pots, move plants under cover during peak butterfly flights. Clip an entire umbel with eggs if you catch it before hatch.

Bacillus thuringiensis kurstaki works on feeding caterpillars that ingest treated leaf -- spot-spray individuals you cannot relocate, not the whole butterfly garden. Insecticidal soap kills soft larvae on contact but also kills syrphid eggs and parasitized larvae. Neem can reduce feeding if applied before larvae get huge; cover both leaf surfaces. Spray at dusk when bees are not on dill flowers. If the goal is habitat, skip sprays and use picking and row cover.