For algae, apply copper sulfate at 2 to 3 ounces per 1000 square feet. Be careful to not overdo this, as copper sulfate can be toxic to grass plants at high doses. To control moss, use iron sulfate or ferrous ammonium sulfate, after spiking or power raking to break up the thick moss layer. The best tact of course, is to not allow compaction, fertility, or especially water management get out of hand. Controlling these relatively simple factors will keep these problems from ever developing .
Many aphids cause leaf discoloration, disfigurement, and occasionally premature leaf drop.
Honeydew covered surfaces will often turn black as sooty mold fungi move in and colonize the sugary substance. Some aphids cause galls. The poplar gall aphids cause marble-sized galls at the junction between leaf blades and petioles on cottonwoods and other poplars. High numbers of aphids can weaken trees and shrubs, but rarely kill them. The sweet honeydew is attractive to ants, flies and wasps.