Lawn diseases are almost as varied as the varieties of grass available. Identification is often difficult due to the varieties. Many diseases are caused by fungi that attack weak lawns. Pests do the same, especially the white grub. Lawns that look yellow and sparse are often being attack by disease or grubs.
Preventing Disease and Grubs
You need to keep your lawn healthy to prevent disease and grubs. Disease takes hold in grass that is not properly taken care of. Fertilization practices applied at the right time and the right amount for the variety grows a thick turf. Regular mowing at the correct height, says North Dakota State University, also helps grow a dense lawn. Cut only one-third of the leaf blade at a time to prevent damaging the grass plants.
Identifying grass disease is often difficult due to the large number of diseases. Contact your local university cooperative extension for a list of diseases that are common for your grass variety. Identify the disease symptoms in your lawn. If necessary, send samples of the lawn to the university extension.
Many diseases in the lawn are caused by fungal infection. You need to identify the fungus before you can buy an appropriate treatment. Fungicides are chemicals used to kill fungi. The wrong fungicide for the situation will fail to work and may damage other plants in the landscape. Pesticides to kill grubs or other insects must be applied according to the label instructions.
Grubs are a common affliction in home lawns. The grub is the larval form of dirt-dwelling beetles, such as the Japanese beetle and the masked chaffer. A small population of grubs is present in most lawns. Grubs become a problem when the population is larger than the turf's threshold. Sample the soil by cutting a 1 square foot section from the turf, says the University of Missouri, and examine the number of grubs present. Between five and 10 grubs is usually above the threshold level.
Growth and Control
The grub grows in three stages, or instars. During the first stage the grub feeds on the roots of the grass, weakening the leaves. Grubs burrow further into the soil during the winter to protect themselves against the cold. During the third stage of development, the grub moves back to the surface to feed again then emerge as a full-grown beetle. Apply pesticides in the fall, during the grubs' first stage of development, according to the package instructions.