Tomato hornworm: how to recognise and treat it

Pest

Symptoms

Thick green caterpillars up to 10 cm long with a horn at the rear end and eight white V-shaped stripes on each side; the similar tobacco hornworm has seven diagonal stripes.
Whole leaves and small stems eaten; a heavy attack strips the plant quickly.
Large pieces chewed out of green fruit.
Large black or green droppings on the ground under the plant — often easier to spot than the well-camouflaged caterpillar.
Round to oval eggs about 1.5 mm, white to light green, laid singly on leaves.

Hand-pick the caterpillars or snip them with shears.
Spray Bacillus thuringiensis (Bt) while the caterpillars are still small; follow the label.
Leave caterpillars that carry small wasp cocoons on their back — the parasitic wasps kill them and breed more wasps.

Spinosad against small caterpillars; follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Check the leaves for eggs and young caterpillars from midsummer, when hornworms are most common.
Spare natural enemies — Trichogramma wasps attack the eggs and other parasitic wasps the caterpillars; they normally keep numbers low.
Dig or rotavate the bed after harvest to destroy the pupae in the soil.

Figures checked against these sources.