Q.What makes a tomato leaf curl up?
What makes a tomato leaf curl up?

Certified GKH Gardening Expert
If the leaves are curling and there is little yellowing on the plant, the curling is likely environmental and not an issue. If the plant is yellowing as well, especially accompanied by spotting or wilting, it is likely disease. If they are diseased, there is little to do but pull up the plants and rotate new plantings to a new location. This article will provide additional information: https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-leaves-curling.htm