Darrell Blackwelder column: What’s the deal with dodder?

Published 12:00 am Sunday, July 25, 2021

One of my traveler friends sent me a photo of her flowers invaded by a strange, almost alien-type growth. A yellow, spaghetti-like plant called dodder seemed to come from nowhere and entangled her bedding plants and shrubs.    Dodder is an annual parasitic plant that consists of thin thread-like stems that are bright-yellow to orange in color. The yellow parasite quickly attaches itself to a host plant. Dodder is a rather unusual parasitic plant with no leaves which extracts water and nutrients from its host plants.

Dodder does produce seeds which have the capability of surviving in the soil up to 40 years! So, once this plant becomes well established, eradication is almost impossible.

Physically removing the parasite can be attempted, but once established it is almost impossible to avoid damage to its host plants. Unfortunately, removal of both dodder and host plant is recommended to ensure eradication.

Control with pre-emergence herbicides is somewhat effective; however, these products must be applied prior to germination. Unfortunately, some pre-emergence herbicides damage a variety of bedding plants and perennials. Many bedding plants are sensitive to pre-emergence herbicides so always check the label before application. Glyphosate (Roundup) will kill dodder, but may kill or severely damage the host plant. Depending on the type of planting, soil sterilization may be a viable option to consider. Soil sterilization using a clear plastic mat to bake the soil will help reduce dodder seed. Apply plastic now and allow the summer heat to destroy all seeds and disease problems within the soil. Go to https://plants.ces.ncsu.edu/plants/cuscuta-compacta/ for more detailed information.

Darrell Blackwelder is the retired horticulture agent and director with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu.