What Is Causing Tan Spots on Leaves ? - Ask Extension
The photo shows tan spots on Marigold leaves, but other plants are also affected.
Sunny location with Tomatoes, beans, watermelon. No mulch. There's ...
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What Is Causing Tan Spots on Leaves ? #362174
Asked September 13, 2016, 9:14 AM EDT
The photo shows tan spots on Marigold leaves, but other plants are also affected.
Sunny location with Tomatoes, beans, watermelon. No mulch. There's a brick wall a few feet behind it.
Watered with soaker hoses. Although it might've been watered from overhead a couple times.
Montgomery County Maryland
Expert Response
It is hard to say for sure what is going on here. How does the whole patch look? Is it blooming? Any problems with the flowers?
Marigolds are generally pretty tough, and anything that does bother them tends to be outgrown.
Possibilities that come to mind include rasping damage from plants bugs or tiny thrips (look for insects, but they could be gone now). We see a squiggly line or two which suggests a leaf miner that feeds between the leaf surface. They are not serious either.
Another possibility is a disease of some sort like botrytis, but that would likely eventually show up as a hairy, grey mold on the flowers too.
This late in the season we wouldn't worry too much and do not recommend control.
You might consider pinching some of the plants to increase airflow. Do the soaker hoses spray up droplets? The leaves in your photos look wet, which would encourage disease.
cm
Marigolds are generally pretty tough, and anything that does bother them tends to be outgrown.
Possibilities that come to mind include rasping damage from plants bugs or tiny thrips (look for insects, but they could be gone now). We see a squiggly line or two which suggests a leaf miner that feeds between the leaf surface. They are not serious either.
Another possibility is a disease of some sort like botrytis, but that would likely eventually show up as a hairy, grey mold on the flowers too.
This late in the season we wouldn't worry too much and do not recommend control.
You might consider pinching some of the plants to increase airflow. Do the soaker hoses spray up droplets? The leaves in your photos look wet, which would encourage disease.
cm
