Tuesday, August 11, 2015

Featured Diagnosis: Dodder (Cuscuta spp.)

Image of the parasitic plant, dodder
Large mats of dodder parasitizing weeds on a disturbed
road side site. (Photo J. French NMSU-PDC) 
Environmental conditions across the state are perfect for the parasitic weed, dodder, to germinate and grow. This parasite does not have leaves and cannot produce chlorophyll. As such, it grows on other plants, using them for water, nutrients, and carbohydrates. It is common along road sides, but can also grow on crop and landscape plants. In the spring, dodder seeds germinate near the soil surface and send up slender, thread-like twining stems varying in color from pale green to yellow or orange and without any cotyledons (seed leaves). The slender, leafless, thread-like stem sways or rotates slowly until it touches the stem or leaf of another plant and begins to wind around it. On a host plant, the dodder stem will immediately form small appendages called haustoria (tiny sucker-like roots), which penetrate the stems or leaves so that dodder can extract its necessary growth requirements. Soon after attaching to a host plant, the lower end of the dodder withers and breaks its connection with the ground, while the upper part of the stem grows rapidly, often forming dense stringy masses. However, if the dodder seedlings are unable to contact a susceptible host plant soon after germination, they will not survive. The damage of dodder to the host plant varies from moderate to severe depending on the growth of the host plant and on the number of haustoria attachments to the host plant. Dodder infestations reduce crop yield and increase harvesting costs for crops like alfalfa. 

For more information please visit Dodder (Cuscuta spp.)

Image of dodder in a native landscape
Dodder in a native landscape setting. (Photo L. Beck NMSU-PDC)

Microscopic image of dodder infecting a host plant
Dodder haustoria (tiny sucker-like roots) penetrating the stem of a host plant.
The parasite uses these projections to extract the necessary nutrients
(Photo J. French NMSU-PDC)

Image of dodder flowers
Small clusters of dodder flowers forming along the stem. Each flower will
produce a small seed pod with 2 to 4 seeds. (Photo J. French NMSU-PDC)

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