The Q&A Archives: Pests on Geraniums

Question: White flies and green worms will not leave my geraniums alone. I've tried spraying with Ortho products but they keep coming back. And snails are eating the leaves. Please Help!

Answer: There are a number of biological controls that you can try to get rid of white flies. Depending on whether the infestation is inside a greenhouse, or out in the garden, there are several natural enemies that you can purchase to help control the white fly population.

Encarsia formosa is a predacious wasp that visits gardens regularly, or can be purchased and released inside greenhouses to control white flies. The wasps are available through: American Insectaries, Escondido, (619) 751-1436, Applied Bio-Control, (209) 874-1862, and Beneficial Insectary, (800) 477-3715.

If you're dealing with an outdoor white fly problem, you might want to try releasing lacewings or minute pirate bugs, both available through the above suppliers.

Other control methods include yellow sticky traps - basically cardboard painted bright yellow and coated with mineral oil or petroleum jelly, and suspended near the tops of plants. Insecticidal soaps work well against white flies, too. Just be sure to spray both top and undersides of leaves. Insecticidal soaps can cause burning of leaves if applied during hot weather, so use caution.

You may be dealing with geranium bud worms, which are difficult to control except by picking off the affected buds and destroying them. The worms hatch from eggs laid on the surface of the buds, and the larvae bores into the bud and eats its way out. While it's inside the bud, no chemical can reach it. I'd inspect the buds for a tiny little entrance hole and pick off the buds that are suspected of harboring worms.

If you can see caterpillars on the plants, and don't want to pick them off one by one, you may be able to control them with the botanical called Bt. It's a stomach poison and the caterpillars have to consume some before it takes effect, so expect continued feeding until the caterpillars have ingested enough to do them in. Be sure to read and follow the label directions.

You can use diatomaceous earth (the ground up skeletons of aquatic diatoms), or crushed eggshells to deter snails. There's also copper stripping that will keep snails out of gardens. Be sure to remove any potential hiding places for the snails, such as garden debris, boards, etc. You can make traps to catch snails or you can hand pick the critters when you see them. Take a terra-cotta pot and turn in upside-down in the garden, propping it up with a large stone. Snails will crawl in to hide during the day. You can empty the trap each morning and dispose of the snails.

Hope the above information helps you grow healthy geraniums this season!

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