My holly plant has some leaves that look as if they've been burnt with a lighter. Is this some kind of disease? If so, what can I do about it?
That looks a lot like leaf scorch to me. Not a disease but the result of the leaves not being able to transpire moisture due to lack of soil moisture or too much soil moisture.
Here is a link that might be useful: About Leaf scorch
any chance of the lawn being sprayed.. and drift hitting the plant???
a different kind of scorch ...
is it the WHOLE plant.. as in a water issue.. or localized to a specific area???? .. if so.. why that area???
That damage is from last year. Indicates a chronic water shortage last year.
Winter damage is the probable cause. It always helps if you give some sort of indicator of your zone or location. Basically it is a transpirational issue, but very common in temperate zones and some people use anti-dessicants to try to avoid it. I've not found them particularly helpful and it's why in places like the mid-west holly is often planted with the same regimen broad-leaf evergreens like rhodies carry.......protect from winds, avoid southern exposures.