Hardy geranium

Vine weevil

What you will see

Adult beetles notch the leaf edges; grubs eat the roots, the plant wilts, especially in a pot.

How to protect

1. Prevention

   • Check potted plants especially in fall and winter.
   • Encourage natural enemies (birds, toads, hedgehogs, ground beetles).
2. By hand summer; losses mainly September to MarchIn the evening, collect adult beetles with a torch; if a plant wilts, lift it and remove the grubs from the roots and compost.
3. Biological August to early SeptemberNematodes (Steinernema 5–68 °F, Heterorhabditis 12–68 °F) into warm soil while the grubs are small; they work poorly in dry and heavy soil.

Geranium sawfly

What you will see

Small holes in leaves from gray-green caterpillars up to ½ in; the damage is only unsightly.

How to protect

1. Prevention

   • From May, check the plants.
2. By hand May and SeptemberPick off the caterpillars by hand.

Slugs and snails

What you will see

Eaten holes in leaves and young shoots, at night and in damp weather.

How to protect

1. Prevention

   • Water in the morning, not in the evening.
   • In winter turn over the soil and remove fallen leaves — birds will pick out the eggs.
   • Encourage natural enemies (birds, toads, hedgehogs, ground beetles).
2. By hand evening, spring to fallCollect slugs and snails in the evening by torchlight on a warm, damp night; traps made of hollowed-out citrus peel or small containers of beer sunk into the soil — empty them in the morning.
3. Biological spring to early fallPhasmarhabditis hermaphrodita nematodes (they work on slugs, hardly on snails); apply to moist soil at 5–68 °F.

Powdery mildews

What you will see

White powdery coating on leaves and stems.

How to protect

1. Prevention

   • Plant in a sunny, airy spot with good drainage.
   • Water in dry spells; plants that dry out are more susceptible.
   • Do not over-feed with nitrogen.
   • Water in the morning and do not leave leaves wet for long.
2. By hand summer, fallCut out affected shoots; in fall remove and destroy fallen affected leaves.