The weather can be blamed – at least in part – for the occurrence of basil downy mildew in the garden.
If you aren’t sure your plants have it, here are the signs:
You notice the leaves are yellowing and then the plant gets brown areas. The underside of the leaf appears to be dirty with some white spots you can see with a magnifying glass.
For more information: http://vegetablemdonline.ppath.cornell.edu/NewsArticles/BasilDowny.html
If your basil plant has it, harvest what you can and throw the rest of the plant in the trash….not the compost bins.
Next year, plant basil somewhere else in the garden.