"When we mark the trees, we are looking for signs of the disease and marking trees that are in severe decline," [Martha Barwinsky] said. "This year, we have seen an increase in the number of diseased trees. We've also been finding we have been getting more hot spots throughout the city." The hot spots include Tuxedo, River Heights and Wolseley, areas where some of the city's oldest elm trees are growing, she said.