I have a question about beets.

My beets have not bolted yet but they could!

I am growing Detroit Deep Red beets in tampa which is in zone 9. I
have read in various gardening books and in online articles that if
beets are subjected to temperatures below 50 degrees for more than two
weeks they can bolt, however I am unclear as to what temperature they
are referring to. Are they talking about daytime temperatures not
getting above 50 degrees, or are they talking about nightime
temperatures falling below 50 degrees. Are they referring to
temperatures being below 50 degrees for two solid weeks in a row,
What if the the low temperatures are broken up by spells of higher
temperatures followed by lower temperatures again. Will that make
beets bolt?

The temperatures here have been around 70 degrees in the daytime and
during the night they go down to the 50s, but recently they have been
dipping into the 40's. We had a stretch where the the night time
temperatures reached down to the high 40's and then warmed back up to
the highs 60's or low 70's during the day for about 5 days, we are now
going to have stretch where the night time temps are going to be in
the 50's for about 3 or 4 days followed by night time temperatures
will be in the 40's again for about 4 or 5 days. will these
temperatures make my beets bolt.

Also I have been getting some spots on the leaves of the beets, i
think that this is a cercospora fungal infection or perhaps some other
fungal infection. Is there an effective treatment for this?

thank you
tampagardener