Dodder infestations in greenhouse settings are uncommon. Usually, it comes down to three different avenues for introduction into the greenhouse. The first is in seed-based crops in which dodder seed could be a contaminate. Seed suppliers are careful in the screening process, and these instances would be rare.
A second more probable cause is that dodder seed may come in with the substrate. Seeds can lay dormant for years and then get mixed into the substrate along with the peat or bark. In the case of a North Carolina greenhouse back in 2014, either of these options could have occurred with their single contaminated vinca plant.
The third possibility is the introduction into the greenhouse from infected plants. If a supplier has an infestation and they ship contaminated plants. This usually is only the case with perennial or woody species.
Dodder does not photosynthesize, so it is classified as a plant that is dependent on a suitable host to survive (a holoparasitic plant). At the beginning of its lifecycle, the dodder seed germinates and must find a suitable host within 5 to 10 days, or the seedling will die. Dodder has the ability to find surrounding plants by detecting airborne volatile organic compounds. Once a host is found, dodder will entwine it and develop haustoria (taproots) that penetrate into the leaf or stem vascular system and utilize the host plant as a nutrient source. Most dodder species lack chlorophyll or true leaves, and the only way they can survive is to parasitize a host plant to obtain nutrients. Once the haustoria have become established, the original root system of the dodder dies.
Dodder infestations have been reported on the following ornamental plants: chrysanthemum, English ivy, fennel, impatiens, marjoram, mint, morning glory, periwinkle (vinca), petunia, perennial phlox, and summer savory (UC-Davis, 2010). Tomatoes are also a preferred
host. Dodder has a wide hose range and will grow on many species in nature.
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