When Summer Drought is Not Drought
The colors brown to brownish tan are often associated with turf during the summer months. The most common cause associated with brown colored turf is drought. A lack of adequate moisture over prolonged period results in the turfgrass plant slowing and eventually ceasing growth. The result often is the plant sacrifices leaf tissue growth resulting in the brown to tanish white colored leaves. This sacrifice is done to protect the survival of the plant crown. Depending on the turfgrass species, once water or rainfall occurs in sufficient amount, new growth occurs from the crown.
Unfortunately, the addition of water does not always result in the turf “greening-up”. Other stresses, specifically insect pests. As we move through the summer insect damage often is confused with drought symptoms. The insect pests that can potentially cause extensive turf damage are:
Billbugs (weevils): Two major billbugs that can cause damage are bluegrass billbug and hunting billbug. In the case of the bluegrass billbug the adults lay their eggs in the stem of Kentucky bluegrass plants in late spring. These eggs have or will hatch shortly producing larvae that will begin to eat its way down through the sheath and crown of the plant. Symptoms appear as irregular patches that are often misdiagnosed for drought stress. A diagnostic method for determining the potential injury from billbug is to tug on the damaged leaves. If the stems break off easily at the crown, and the stem is hollow, with sawdust-like material, billbug is the most likely culprit. The hunting billbug follows a similar life cycle as the bluegrass billbug, but in this case the hunting billbug attacks warm season turfgrasses. Actually, you do not really see the damaging symptoms from the hunting billbug until fall.
Black Turfgrass Ataenius (BTA) – During July drought like symptoms can appear on annual bluegrass turf caused by the BTA grub. With July almost upon us one of the most misdiagnosed problems (and I am sure there are many others) is that of Black Turfgrass Ataenius (BTA) grub damage. Damage symptoms are quite similar to drought injury and often times “poor irrigation coverage” is blamed when it is actually BTA. On Poa annua turf, especially fairways and short cut rough, before jumping at the conclusion it is drought injury, check under the turf to make sure grubs are not present. The BTA grubs are small with legs and usually present in high numbers. In addition, in some instances BTA damage can also look like anthracnose. Again, take the time to check for BTA grubs.
Chinchbugs – Hairy Chinchbug can infect cool season turfgrasses, while the southern chinchbug infects warm season turfgrasses. In both cases severe damage can occur with symptoms similar to drought. The southern chinchbug is a serious problem on St. Augustinegrass and cause severe injury through the fall. The southern chinchbug can go through multiple generations in a growing season and thus are a persistent problem. Chinchbugs can be spotted in the turf and are characterized having short wings (they do not fly) and are moving slowly.
Grubs - Grub damage as previously discussed in a past blog appears much like drought injury. The symptoms often appear during early to mid-fall. The key diagnostic key is to see if you can pull the turf back like a carpet. If you can that means grubs have severed the root system. You should be able to spot the grubs too.
Insect Control: Insect pests of turf are often difficult to control from a cultural or genetic control. Culturally, you may be able to mask the symptoms by providing water to sustain growth or promote recovery but eventually symptoms appear. Genetically there are turfgrass plants that are more resistant to insect injury as described above like tall fescue (a cool season turfgrass) or resistant chinchbug cultivars of St. Augustinegrass. The most effective means for controlling the above insects is preventatively with an insecticide like Acelepryn.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: