How to apply sub/gsub of awk on a particular field?

I got a file with contents are of the following format

...
2007-09-28 ./.passwwd1.sh.swp
2007-11-26 ./827-55.jpg
2007-09-28 ./argcheck.pl
...

I have to delete all the '-' in the "first field", ie. the date, not on the second field, which is the name of the file.

i.e.
required output

...
20070928 ./.passwwd1.sh.swp
20071126 ./827-55.jpg
20070928 ./argcheck.pl
...

How to apply sub/gsub of awk on a particular field?
Could anyone please help me.

Try:

 awk '{gsub(/-/,"",$1);print}' file