Hydrangeas and Caterpillar Control

Q. I had a horrendous caterpillar problem last year. Can I use a systemic insecticide to control them much like I do with Aphids?

Caterpillar of the Giant Peacock Moth, Saturnia pyri

Caterpillar of the Giant Peacock Moth, Saturnia pyri

A. Systemic insecticides will not control chewing insects like caterpillars, or beetles. They do a wonderful job with Aphids, Mites as well as other sucking insects. These insects feed on the plant juices and also ingest the insecticide, which then controls the population. With chewing insects like caterpillars, these chemicals have no affect. You first need to be diligent in watching the host plants for the first sign of the problem. The caterpillar and worm season begins just after Memorial Day and extends into the early fall. Petunias, Geraniums, Flowering Tobacco and Tomatoes are the primary host plants for worms. In addition, there can be several batches of the same problem during the season, so the host plants need to be checked weekly. I wouldn’t spray until there’s a problem or, you could just pick them off the plants and dispose of them. BT (Bacillus Thuringiensis), is an organic solution that gives the caterpillars or worms a fatal case of the stomach flu; however, it doesn’t work immediately so you have to be patient. Spinosad is another organic solution that will kill the caterpillars on contact and provide some residual control. Captain Jack Dead Bug Brew by Bonide is one of several products. Both of these solutions are widely available. In summary: Be diligent, monitor your plants, and react when necessary.

Q. My hydrangeas grow into beautiful plants each year but do not flower. What do I need to do to encourage them to bloom? I tried 0-10-10 in the past with no success.

A. The failure of Hydrangeas to bloom is not a fertilizer issue. Pruning too heavily causes the lack of flowers or sparse flowering. This tends to be a problem with mature plants in older neighborhoods. Hydrangeas bloom on the second year wood. When the bushes are pruned severely, all the flowering wood is removed. Many times this is the result of inexperienced gardening services. They can maintain grass well but their horticulture is a bit shaky. The Hydrangeas will flower next year, even if you trim the plants lightly this year.

Note: For those looking to replace or plant new Hydrangeas, you can avoid this problem with the Endless Summer varieties. The Endless Summer Hydrangeas bloom on both old and new wood. You get the wonderful flowers every year, whether or not your gardener trims it at the wrong time or too vigorously. Available at your favorite garden center is the standard variety or the lace cap variety, Twist and Shoot.

Buzz Bertolero is Executive Vice President of Navlet’s Garden Centers and a California Certified Nursery Professional. His web address is www.dirtgardener.com and you can send questions by email at dirtgarden@aol.com or to 360 Civic Drive Ste. ‘D’, Pleasant Hill, Calif. 94523 and on Facebook at Facebook.com/Buzz.Bertolero

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