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Photo of ants and white spores

I planted my gardenia four or five months ago.

I noticed, recently, that (a) growth has stunted, and (b) there are ants all over the plant (base, leaves, etc.).

There are also white little dots (spores?) on some of the leaves.

To help with the stunted growth, I've started fertilizing with a more-acidic fertilizer as opposed to the more general-use plant food I had been using.

Couple details about environment:

  • I live in South Florida
  • It's rained 3-5 days a week for the last couple months
  • Plant gets plenty of direct sunlight

So, a couple questions wrapped together:

  • What are the white dots, and how can I get rid of them?
  • Are the ants all over the plant a bad thing, and, if so, how can I get rid of them without harming the plant?
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up vote 5 down vote accepted

Mealybug are whitish and have a white fluff around them. Scale is hard, semi spherical and brown to black. Scale and aphids both secret a sugar that ants harvest. You haven't seen a real scale infestation until you walk under an indoor tree and notice that your shoes stick to the carpet.

In the picture above the oldest adults are dark brown and the youngsters are light brown. They move out up and down the leaf vein where the flow of sap is the strongest.

Scale are difficult to eradicate as the hard shell protects them from soap and water. However a soft tooth brush dipped in soap and water would be effective in removing the adults. Use the toothbrush once and then wipe the leaves and stems, top and bottom, with a cloth or paper towel soaked in soap and water at five to seven day intervals to catch the eggs and stragglers.

High nitrogen levels will attract scale but the most likely source is that they came with the plant from the grower. If the grower only had them under control and not eradicated the scale will return as they can hide in the axils of the leaves.

Thanks to GradyPlayer for pointing out that the two are related. Even with their different lifestyles they are both hard to control on houseplants. As a former licensed pesticide applicator I found that if soap and water doesn't remove them then pyrethrums, neem oil or registered pesticides are not 100% guaranteed either. It's not what you use, it's the coverage. Can you get your choice of control agent to cover the entire surface of the plant and can you get the same coverage when you repeat the treatment at five to seven day intervals?

Edit: Magzalez asks

  • What are the white dots, and how can I get rid of them? They are scale insects and you can use a variety of methods but success involves covering the entire surface of the plant at five to seven day intervals with your choice of soap, neem oil or dormant oil. Best methods with scale involve physically removing them.

  • Are the ants all over the plant a bad thing, and, if so, how can I get rid of them without harming the plant? The ants are there for the plant sugars the scales excrete. Remove the scales and the ants will go away. They are farming the scale and are not directly harming the plant.

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yup looks like scale to me, neem oil seems to do an alright job of killing adults, where pyrethrum doesn't seem to touch them. eradication probably not possible, but control is. – Grady Player Oct 10 '12 at 17:18
and to be pedantic, entomologically speaking... mealybugs are a type of scale insect. – Grady Player Oct 10 '12 at 17:20

It's probably mealybugs, being farmed by the ants. Like aphids, the mealybugs suck the juices on the new growth and cause deformity and discoloration. Spray with white oil or garlic infused water over several days/weeks. Over-fertilizing can cause soft growth that bugs opportune. A drench with a diluted seaweed solution helps strengthen cells.

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I have had great luck with scale using a dormant oil spray. It essentially coats the shell of the insects and suffocates them. You can also simply spray the plant with a high pressure spray from a garden hose.

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