Spots... I see spots!!!

Have you ever wondered what was happening when you saw spots? I ain't talking about those specks that dance in and out of your vision, but those blemishes that appear now and then on plants and usually signals the death knell for your garden. Where your plant leaves should be bare and perfectly green - there, those spots now appear... (does this remind you of the "Out damned spot, out!" scene in Shakespeare's Hamlet?)

Spots can signal one of three things:
1) nutrition deficiency
2) fertilizer/pesticide damage
3) presence of plant pathogens

As a plant pathologist (yes, a little self-promotion here...), I am familiar with all three, but will concentrate on the last item. First of all, foliar spots need not be a bad thing, as long as they are contained (i.e. managed so that they do not spread to other plants in your garden). In many cases, it will only be one particular plant species you have in your garden - in this case, the pathogen is said to be specialized; it will only affect that species and its close cousins. In the extreme case, all of your plants will be affected - the pathogen is then a generalist.

There are a few things you can do outside of applying industrial-strength fungicides and/or bactericides. First of all, identify whether it's just the one plant, or multiple plants. Second, observe the kind of symptoms you're seeing. Third, determine your course of action.

Courses of action:
1) cut off all of the affected leaves, being sure to sterilize your cutting implement in between cuts (a 1:3 solution of bleach/water as a sterilizant will do the trick here). Ensure you carefully package the affected leaves and dispose of them properly to prevent spread.

2) gather up all dead leaves on the soil top.

3) wait one week, then observe remaining leaves carefully. If the spots reappear, this usually means there's another means by which the pathogen is being applied... (here's where you say "geez, it's coming from the neighbor's garden!!!")

4) check and see if there are any insects (this is also a good idea while implementing the first step) as these are common vectors for pathogens.

5) decide which is best: a general pesticide for the insects, or a fungicide/bactericide. There are several available through hardware stores and garden shops for regular garden use. However, they're useless unless you know what you're attacking! For example, never use a fungicide for a bacterial disease...