Overall, the black-eyed Susan vine (Thunbergia alata) is pretty much pest- and disease-free. On occasion, however, certain insects and disease can infest your black-eyed Susans. They can be treated through a few, simple steps.
A mound of flying white bugs on the Black-eyed Susan is a signal that whiteflies are on the attack. Start with an organic defense. Place aluminum foil under the plants; the foil repels whiteflies. Follow with a medium intensity spray of water to wash them away. In worst cases, try those yellow sticky traps to snare and kill whiteflies.
Spider mites are tiny, pesky insects that produce a sticky, dewy web that will cover and infest the leaves and flowers. Try a natural predator to get rid of them — ladybugs. If infestation is intense, resort to a miticide as recommended by your garden center or local cooperative extension office.
Look underneath the leaves of your Black-eyed Susan. If you see bumps and the leaves have begun to yellow, the plant may be infected with scales. These relatives of mealybugs can weaken the plant and make the leaves drop off. Additional signs are ants and a dewy substance on leaves and flowers. Stop the progress of scales by immediately isolating the plants and pruning infected areas. Scales can cause fungus and sooty mold to develop. Contact your local extension office for remedies that work in your area.