Q.Late Summer Care For XXL Mandevilla Agate White
Vines are planted in the ground, supported by a trellis. All six vines showing poor leaf color, health, some curled leaves. San Diego, September. Should I address fertilizer needs or suspend any attention until early spring?
Certified GKH Gardening Expert
They are heavy feeders and need regular fertilization throughout the summer. But since it is getting late in the year, I would suspend further feeding unless you want to add some compost to the soil. It looks like pest damage, i.e., the mottled foliage could mean spider mites. Also, the blackish mold could be the result of honeydew, which is produced by aphids and scale. To combat all of these, spray the front and back of all the leaves with Neem oil. You can remove the worst looking leaves.
The leaves with tan spots and yellowing could have anthracnose. The article below tells what to do in that case:
