The leaves on my tomato plants are turning yellow, and the plants seem to be dying. This started on one plant but has now spread to the neighboring plants. There are several diseases killing tomato plants in New Mexico this year.
Some diseases are viral and others are fungal.
In both cases, you should remove diseased plants. I spoke to Dr. Natalie Goldberg, NMSU Extension Plant Pathologist, who thinks you have described curly-top virus symptoms. She is getting reports of extensive curly-top problems from many parts of New Mexico. In this case, removal of infected plants is especially important. Curly-top virus is spread from plant to plant by small beet leafhopper insects.