Question
I run an organic community garden in Tampa, Florida and I just read a 2006 answer of yours regarding the leaf curl on tomato plants issue.  I was hoping to find out if it could just be over watering since our plants were just transplanted into a lasagna layered bed.
The sunflower plant was in a container bed (kiddie pool) where we did not see any other plants (a few different varieties - watermelon, squash) experience the same curl.  When we pulled the sunflower - there were no aphids.
We do have the soil of the tomatoes "mulched" with fine hay to retain moisture but, have differing opinions on what kind of soil they like.  Sandy, dry, soil is one opinion and ranges all the way to watering every day and really soaking the soil.
I've noted that my home tomato plants look great with very little compost (they're volunteers from my last batch of compost) and quite sandy soil a few inches below.
If you have any other recommendations - that would be great.

Answer
The most likely cause is excessive watering. Sunflowers do not like "wet feet". This causes the roots to become water-logged, which in turn inhibits the plant's ability to take in oxygen and nutrients.

With sunflowers, always allow the soil to dry out between watering. These plants can take light droughts with no ill-effects. This should take care of the problem.

Good luck, and best regards.

Mike