A tree killer is on the loose in San Francisco.

Golden Gate park officials report that someone has damaged or chopped down 45 trees in the last two months, according to Bay City News Service. Casualties include 15 elms and a sycamore in the Music Concourse that were sawed down and a magnolia that was cut in half— just in the last week.

In June, a dozen young cypress and pine trees were uprooted, and the bark on mature cypress trees was stripped. The motivation is unknown, and the park has cranked up its nighttime patrols.

The news of this arborcide comes on the heels of a report of an attack that killed some 100,000 honey bees at Hayes Valley Farm recently. Someone pumped pesticides into hives, wiping out most of the residents. Bees have been beleaguered in recent years. Colony collapse disorder, a mysterious phenomenon, has damaged the bee population, which many commercial agricultural enterprises depend on to pollinate their crops and orchards.