Question: Dipladenia with new brown leaves
I would like to ask for advice for my Dipladenia.
It was great until ten days ago. All dark green and bright leaves, a couple of buds. Then, I don't know if with the arrival of the heat (I live in Barcelona), some leaves started to turn yellow. If I look under the leaves, the lower surface has green dots, like bubbles.
But the thing that worries me most is that I have now noticed that the new leaves are brown and curled ...
There are too many things that could be the cause, and I would like to go by exclusion until I consider the (or the) most likely, to act accordingly:
1) could it be the heat (it is exposed only to the morning sun, until midday)?
2) the red spider mite (I have some on other plants, but I haven't seen any on Dipladenia yet)
3) have it fertilized? A month ago I spread a few tablets of fertilizer in granules (about fifteen, on a 18 cm diameter pot)
Thanks in advance!
Answer: Dipladenia with new brown leaves
let's say that all the causes you indicate may have contributed to the conditions of your dipladenia:
- dipladenias love semi-shaded positions; tolerate direct sun, but possibly only for a few hours a day; unless they belong to the sundavilla variety, which loves direct sun, even all day long.
- maybe the fertilizer is too much, but if you have used a granular fertilizer you should be able to remove about half of the granules (although in fact, it does not seem to me that it is an excessive quantity).
- in all likelihood your dipladenia has been attacked by some parasite, such as mealybug, red spider mite or aphids; the bubbles under the leaves suggest the cochineal, which, together with the red spider mite, refers to a warm, dry and poorly ventilated climate. To eradicate these insects you can try with a systemic insecticide-acaricide, that is to be supplied in the irrigation water, and enter the circulation in the plant. In this way it should not create problems for useful insects that settle on flowers, but should defeat all insects that feed on leaves. Look for a systemic insecticide and acaricide in the nursery, asking the nurseryman for advice if necessary; these are specific products, which must be used in the ground and not sprayed on the leaves; they also exist in tablets, to be put in the pot, which melt every time you water. Always check that the insecticide you are using works against the insects or small spiders you want to get rid of; and therefore on the label the insecticide must specify to work against the cochineal, and also to be an acaricide (the red spider mites are not insects, and most of the insecticides leave them perfectly free).
In any case, since these are insects that develop in very hot, dry and poorly ventilated conditions, try also to move (if possible) your dipladenia in a slightly more shady and possibly even more ventilated area; and when you remember, in addition to watering it, vaporize the leaves with distilled water.