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Garden Pests and Diseases: Plumbago issues: Stem mold, Black Spots, Wilt & more...

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Forum: Garden Pests and DiseasesReplies: 5, Views: 67
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Lady's Island, SC
(Zone 8b)

September 15, 2012
3:09 PM

Post #9276122

I have 9 Imperial Blue Plumbago plants I planted earlier this summer. 7 of them, which are in the backyard 10 to 15 feet apart or more) are having issues. The other 2 in the front and side yard haven't shown any issues yet. All have been thriving for 3 months until recently...Not sure what is going on.

The issues:

(Pic #1 and #2) One Plumbago had this white/grey mold 1/8" thick growing on its main stem from the ground level to about 3 inches above. Also, some leaves in this area had some "sooty" mold on them. Upper leaves looked ok other than a few leaves having some black spots on them. These black spots also appeared on at least 2 other Plumbago within the last few days. Soapy water removed the sooty mold from the leaves and even washed away the stem mold for the most part. I saw remnants of the mold today & decided to take a picture to see if anyone knew the issue and cause. Regarding the black spots on the looks as if oil were dripped on them, but I know that has not happened. It also does not come off with soapy water.

(Pic #3) One of the Plumbago that has the wilting issue also had leaves with chew holes and leaves have patched that are almost see through. What critter is causing this? And what should I do to take care of the situation?

(Pic #4) 2 Plumbago plants which are on opposite sides of my backyard have at least 1 branch of leaves that are wilting/dying while the rest of the plant appears to be thriving. What could be causing this? And how would I go about treating it? In this picture, the wilting is on the right side.

Any help would be greatly appreciated!

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Dublin, CA
(Zone 9a)

September 15, 2012
8:45 PM

Post #9276330

The first picture looks like it could be mealybugs. They can suck the life out of a plant if you don't get rid of them, so they could be causing some of the other stress you're seeing too. They also secrete honeydew which is a great growing medium for sooty mold, so the sooty mold is likely because of them too.
Lady's Island, SC
(Zone 8b)

September 17, 2012
4:41 AM

Post #9277477

ecrane, I looked into mealybugs after your response, and I do think you might be right about the 1st picture. Thank you!


Prairieville, LA
(Zone 9a)

September 20, 2012
10:13 AM

Post #9281123

I agree on the mealybugs. That and thrips and scale seem to be the major insect problems. from all that I have read, there are very few diseases that show up on plumbago and none that are fatal to it.
Clermont, FL
(Zone 9a)

January 23, 2013
8:15 PM

Post #9395532

Bayer shurb and tree drench usually gets rid of lots of different parasites on lots of different types of plants.
Contra Costa County, CA
(Zone 9b)

January 27, 2013
6:45 PM

Post #9399524

Damaged leaves:
Some look like mechanical damage, for example the leaf got injured by a child's toy tearing it.
However, some could be a pest munching on the leaves. It does not look like a lot of damage, though. Maybe go out at night with a flashlight to see if you can find the pest.

"Mildew"- ditto: Meally Bug and Wooly Apple Aphid look similar, and are treated similarly.

A whole branch wilting, others are fine: option 1) Mechanical damage: Did a branch break? If it got bent near the bottom...
option 2) There are several diseases that can enter the vascular system of the plant and cause wilting, often of just part of the plant. Look into Verticillium, Fusarium and similar issues. I am not sure if Plumbago are susceptible to these diseases.

Black spots on the leaves: Look kinda big, but how about the waste matter from certain bugs? Like fly specks, but bigger bugs = bigger poop. Especially if it is on the same plant that might have been somewhat eaten.
Are the black spots sunken in, or any other discoloration?

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