What's eating my chocolate cosmos?

Chocolate Cosmos (Cosmos atrosanguineus) is a tuberous perennial that attracts aphids, slugs, and occasionally vine weevils attacking the tubers. The dark velvety blooms can shelter thrips. Slugs are particularly damaging in cool wet conditions when new growth emerges in spring. Protect tubers in storage from rot and weevil grubs over winter.

Colonies on new shoot tips and beneath leaves, especially on tender spring growth; honeydew attracts ants and sooty mould. Apply insecticidal soap or neem oil spray; introduce biological controls such as Aphidius parasitoid wasps under cover; water-jet outdoors.

Emerging shoots and young stems eaten to stumps; worst in spring as tubers break dormancy; silvery trails mark the damage. Apply iron phosphate pellets around tubers as growth emerges; use copper barriers; sink beer traps at soil level.

Adults notch leaf margins; C-shaped grubs in the soil eat through the tubers, causing sudden plant collapse. Apply pathogenic nematodes (Steinernema kraussei) to moist soil in late summer/autumn; inspect tubers at lifting for grubs; discard infested material.

Silver streaking on petals and leaves; small dark frass deposits inside flowers; blooms look faded and damaged prematurely. Remove and bin affected blooms; use spinosad spray; blue sticky traps help monitor population levels.