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Problem: Billbugs on Turf - Sphenophorus spp.
Plants Affected: Primarily Zoysiagrass and Kentucky Bluegrass
Description: Billbugs are not true bugs but long-snouted weevils. The adult may cause some minor feeding damage to the turfgrass but the “grub” is the stage that can cause serious problems. Billbug grubs are legless and are a creamy-white color with a brown head.
Eggs are laid on blades of grass through late spring and early summer. The young larvae tunnel up and down the stem until they become too large and drop to the ground where they begin to feed on crowns and roots. Maturing larvae may feed several inches deep in the soil.
If billbug damage is suspected, inspect the turfgrass crowns. Infested plants are easily pulled up and separate at the soil surface. The crown area is swollen, hollowed out, and ragged with frass (a sawdust like material) present. Digging into the soil will often reveal the grubs.
Recommendations: Billbugs are one of our most difficult turfgrass insects to control. The adults are well armored and do not ingest insecticide while penetrating a grass stem during feeding. The grubs spend much of their lives boring inside grass stems where they are protected from insecticide sprays. However, adults are easier to control than the grubs because they feed on top of the soil where they are more easily contacted by insecticides. Unfortunately, most people don’t notice them because they do not cause significant turf damage.
Start looking for the adults when the surface of the soil approaches 65 to 68 degrees F. They will often be seen crawling on sidewalks at this time. Spraying for the adults is normally done in late April to May.
Grub damage is often first seen about mid-July. The effectiveness of control is dependent on whether the insecticide reaches the billbugs. If larvae are still inside the stems or if they are deeper than the insecticide reaches, the chemical will be ineffective.
References:
1. Turfgrass Insects of the United States and Canada, pg. 220 - 243
2. Billbugs and White Grubs: Characteristics and Control, Colorado State University Extension Publication 5.516
3. Billbugs in Turfgrass, Ohio State University Extension Factsheet HYG-2502-91
Last Update: 03/28/2003
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