Question
Hi Nick,

I noticed that a couple of the crotons I have in my yard were covered with a black sticky substance (it was all over the fence behind them as well.) I cut them all back and scrubbed the fence.  I was wondering if you know what it is and if it will infect the soil around them.  If so, what can I do to prevent it.  I have a lot of plants in my yard and would be heartsick if it infected my other plants.  

Thank you in advance,
Sue

Answer
Hi Sue, thats Sooty Mold,,,it is an innocous fungus that feeds off the secretions that small insects like Aphids and Scale secrete as they feed; it is harmless but the insects that it is feeding off aren't and need to be addressed. If you spray the plants with a Horticultural Oil, it will kill the insects and loosen the Sooty Mold, where it can be washed off the next day, along with all the dead insects. Apply the Oil in late afternoon, after the Sun has begun to set (oil magnifies the heat and can damage the leaves if applied during the day..)..the next morning,,,go out and wash the plants down with your hose before that days Sun heats up..Nick