QuestionQUESTION: I live in San Diego and have had a trellised Madagascar Jasmine / stephanotis about 6' tall in a 16" pot on my patio for several months. I have it on the shadier side of the patio but it does get morning sun, more in summer. Over the past couple of months, some of the leaves are turning yellow, and those leaves and some others are getting tiny black spots on the undersides, tip end. What is this, and what should I do besides remove them?
ANSWER: The first thing I would do is to determine if the black spots are insects or not. A hand lens or magnifying glass would work to do this. If the spots are raised off the leaf surface take a toothpick and see if there is any liquid in the spots when crushed. If so, your problem may be an insect. Otherwise, the problem may be a water issue. Too much water may be causing the roots to be starved for air. This would result in some of the leaves turning yellow. There is also the possibility of fungal disease, but jasmines are pretty resistant to fungus diseases. Please try to determine if one or another of these situations exists and then reply with a follow-up and I can make a recommendation on what to do. Thanks.
---------- FOLLOW-UP ----------
QUESTION: Not insects. The black spots are recessed, and the larger ones (ca 1/8" diameter) are tan with black edges. I guess the tan parts of the leaves are dead. Some of the leaves are warped, too (actually, the plant had a few warped leaves and leaves with indented edges when I bought it). Some leaves have only the spots, a few are a combination of yellowing, warped, and/or spotted. This is mostly on the lower parts of the plant.
AnswerThanks for the clarafication. I think the plant may have a fungal or maybe bacterial infection, based on the recessed spots with black centers and tan margins. Buy some copper fungicide from a garden center. Fertilome has a product just called "copper fungicide". The copper is active against bacteria and fungi. Mix according to label instructions for an ornamantal plant and treat 10-14 days apart for about 2-3 times. Do not spray the plant in the bright sun as phytotoxicity could occur. Observe where the spots are now and watch to see if they move any further up the plant over that time. The copper should prevent future spots from developing. Those leaves with spots now will have to die and fall off. Make sure you gather those leaves and dispose away from the plant. Good luck.
