Also known as yardlong bean, asparagus bean (Vigna unguiculata subsp. Sesquipedalis (L.) Verde) is distinguished by the edible bean pods that frequently reach lengths of up to 36 inches. The plant, which grows to 9 to 12 feet, is also planted for its ornamental qualities and violet flowers. Asparagus bean is at precisely the same plant family as the black-eyed pea. Although the plant is a legume, it is not related to snap beans or pole beans.
Bacterial Blight
Halo bacterial blight (Pseudomonas syringae pathovar phaseolicola), shows up as wilted foliage and brownish spots that appear on the leaves and pods. The blight is readily recognized because every brown spot is surrounded by a distinct yellow halo. Halo blight often occurs as a consequence of damp, cool weather, as asparagus beans need warm, well-drained soil. Treat affected beans with a copper-based fungicide. To prevent halo bacterial blight, avoid using sprinklers. Instead, keep the foliage dry by watering in the base of the plant. Alternate planting locations at least once every three decades, as the blight stays in the soil for two decades.
Root Rot
Root rots are brought on by fungi that live in the soil. When asparagus beans have been implanted in affected soil, the beans frequently fail to germinate. If they do emerge, then the leaves turn yellow and the plant finally rots and dies. The primary rots affecting asparagus beans are Fusarium root rot (Fusarium solani) and Rhizoctonia root rot (Rhizoctonia solani). Both produce mushy, rotted stems and yellow, withered leaves, as well as red spots at the base of the stems, or on the stem just below the soil. To prevent root rot, find a new spot to plant the seeds following year, as the fungi can dwell in the soil as long as six decades. Keep the region around the plants clean and remove infected leaves. Plant asparagus beans at well-drained soil or raised beds.
Fungal Diseases
Asparagus beans are vulnerable to many fungal diseases in addition to root rots. Fungal diseases include white mold (Sclerotinia sclerotioru), suggested by a fuzzy white material that develops on the stalks, leaves and pods. Likewise powdery mildew isn’t difficult to spot from the white, powdery coating on the leaves and pods. Sometimes, a strong stream of water directed at the affected region removes mould and powdery mildew. Some types of fungal disorder cause dark spots on the leaves similar to halo blight, but without the yellow halo. To manage bacterial disorders, prune and dispose of affected regions. Make sure the plants are not crowded, as asparagus beans requires air circulation. You might need to use commercial fungicides if the disease is severe.
Aphids and Spider Mites
While asparagus beans are affected by various pests, most are nuisances that cause little harm. Aphids and spider mites can cause damage to the plant if left untreated. Spider mites are tiny and difficult to see, but they abandon a fine webbing on the undersides of the leaves. The leaves of a badly infested plant might look scorched. Spider mites frequently appear on plants that are not adequately watered, as the insects like dry, dusty conditions. Aphids are tiny bugs, but they are sometimes seen on the undersides or joints of leaves. Aphids suck the sap from the leaves, leaving a sweet material that frequently develops black sooty mould. Light infestations of aphids and spider mites are sometimes removed with a strong stream of water. Treat heavier infestations with insecticidal soap spray.