Crabgrass is an annual plant that propagates from very small seeds. The seeds typically germinate when the early summer sun is very warm and humidity levels are high. The crabgrass will grow quickly in full sun areas, and seed heads will soon appear. One advantage of zoysia grass is that the plant grows thick and lush. The tightly growing plants can choke out crabgrass if a pre-emergent herbicide is applied to the lawn in early spring.
Apply the pre-emergent herbicide in early spring as night temperatures enter above 50 degrees F.
Mix the herbicide concentrate according to the manufacturer's labeling. Various areas around the country will have different climate conditions. These climate variances may affect the herbicide in negative ways. Mix the concentrate and water inside the sprayer.
Spray the herbicide onto the lawn when the winds are calm. High winds may disperse the chemical to undesirable areas, causing other plants to become infected and die.
Allow the herbicide to completely dry before accessing the lawn. Inspect the zoysia lawn for any emerging crabgrass. You may have to apply a second spray of the herbicide if some of the seeds and new plants are germinating.