Sticky stuff on potted bay tree / Yellow stuff growing on bark mulch
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Issue: September 7th, 1998


Sticky stuff on potted bay tree

Question:

There is a clear sap all over my small potted Bay Tree. I don't want to lose the tree but am not sure how to treat the problem.

Answer:

My first guess is that you have an insect problem. I think you will find brown bumps on the stems and leaves of the bay tree. This is scale insect. You can remove them manually or with insecticide sprays. Since the bay is used for seasoning and may be the reason that you are growing it, if you choose to use insecticides, choose one safe to use on food crops and use it according to the directions.

You can manually remove them by finding each bump and rubbing it off with a cotton swab dipped in alcohol or dipped in cooking oil. Both materials will help kill the scale. However, there are eggs which will hatch and produce a new generation of scale insects. If you can catch the insects before they settle down and build the waxy covering over themselves (the brown bump that you probably found), then you can use insecticidal soap or other insecticides effectively.

If you didn't find these bumps, you probably have a different insect pest. Look for aphids, mealybugs, or other insects. Aphids can be washed off with a hand-held shower spray (put the plant in the shower or bath tub) or, if the plant is small, use the hand-held sprayer found in many sinks. Insecticides may also be used, but are usually not necessary if aphids are the problem. Other insects may require other treatments. Contact you local Cooperative Extension Service office or local garden center for help identifying and managing the pests.


Yellow stuff growing on bark mulch

Question:

I have a northeast-facing garden. It is planted with a crape myrtle and miniature rose bushes and I have spread crushed pecan shells as a mulch. I have found that a vivid yellow substance appears under the pecan mulch and sometimes in small "piles" on top of the mulch. What is this stuff???

Answer:

What you have seen is probably a very interesting organism called "slime mold". It is not a fungus but more like a protozoan. Spores germinate into small (microscopic) organisms that move around, feeding on decomposing organic matter (your pecan shell mulch), then on cue all of these things move together to form the bright yellow structure that you saw. At this time some become spore cells and others become part of the structure. The spores mature and blow away to start the process over again.

The slime mold does no harm to plants. It only helps decompose (compost) the organic mulch. They require moisture to develop and to move around. We see them here in New Mexico during moist periods or highly irrigated locations.