Yellownecked caterpillars have a big appetite as they prepare to cocoon before becoming moths. - Original Credit: For The Baltimore Sun
Yellownecked caterpillars have a big appetite as they prepare to cocoon before becoming moths. - Original Credit: For The Baltimore Sun (Ellen Nibali / HANDOUT)

These caterpillars have denuded whole branches of my small tree! What’s the best way to get rid of them?

Gregarious aren’t they? These are yellownecked caterpillars, one of many caterpillar species with big appetites. These native caterpillars like to arch into a U.

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Fortunately, by late summer trees and shrubs have had plenty of time to carry on photosynthesis and build up energy reserves. They don’t mind losing a few leaves to hungry caterpillars. Yellownecked caterpillars currently munching on shade and fruit trees will soon be dispersing and making cocoons, then turn into moths.

If you have a new young tree that is getting totally defoliated, though, you should take action. Manually pull them off and drop into soapy water to drown. Otherwise, leave them be and consider them bird food.

My tall phlox got a brown dieback starting at the bottom and working up the stalk to the flower. Is this a disease, fungus, insects or mildew? Anything I can do?

Phlox are susceptible to several fungal diseases that start at the bottom and move upwards, such as powdery mildew or leaf spots. In those cases, you would see the fungal spots or the white-gray blotches of powdery mildew before the leaves turn brown.

If you do not, we suspect a crown rot or Southern blight is infecting the crown and roots. In that case, remove the plant. To confirm the diagnosis, first search ‘Southern blight’ on the University of Maryland Extension’s Home & Garden Information website. For Southern blight you also must remove the top layer of soil about 1-2″ deep around the stems to prevent Southern blight spread or infection of a new plant.

Powdery mildew is such a common problem with tall phlox that several good disease-resistant varieties are available.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.

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