My Basil Plants Are Covered With Green Stringy Stuff

Appearance

• Dodder was classified as a member of the Convulvulaceae, or morning glory family, until recently and strongly resembles the snarls of tendrils you see on twining morning glory plants. More recently, dodder has been reclassified into its own family, the Cuscutaceae. Aside from some small nodules, dodder classically appears as nothing but endless stems, wound around and draped over the increasingly sickly plants it infects. Stems may be yellow, orange, greenish or even reddish, depending on carotenoid content. Dodder has no natural chlorophyll except in the stems and buds, meaning even its green shades have a yellowish tinge.

How Dodder Works

• Like any parasite, dodder needs a host. As a bindweed, dodder travels by twining. Seedlings wrap counterclockwise around stems of host plants, and rootlike protrusions called haustoria penetrate the cuticle of the host to access nutriments from the plant.

Plants Dodder Favors

• In commercial agriculture, dodder is of particular concern to growers of potatoes, flax, alfalfa, and clover. Dodder also infects beets, cucumbers, tomatoes and basil. Dodder may not only weaken plants but also may be the carrier for a group of damaging plant diseases informally grouped as the "yellow" diseases. Many tender annual bedding plants are susceptible to attack, among them petunias, impatiens and dahlias. Chrysanthemums and other members of the daisy family are particularly prone.

How Dodder Spreads

• Tiny seeds are produced in the millions and can be spread through irrigation water, animal digestion and intermixing with other seeds, like clover or onion seed. Dodder varieties adapt to different growing conditions, some requiring moist soil, others able to survive in fairly dry brushland and remaining hardy from zones 4 through 11. In Southern states, dodder may be a perennial. Even farther north, where dodder is, by and large, an annual, seeds can stay viable in the soil for five years or longer.

Eradication

• Only two methods work well to control and remove dodder. Pre-emergent herbicides like Dacthal can be applied before seedlings sprout in the spring with good results. As with all herbicides, follow directions carefully. Dodder can also be pulled, although this must be done before seeds emerge. In areas too large to pull, gardeners get best results by removing all host plants along with this parasitic weed.