For those of you who experienced the army worm invasion of 2021, I’m confident you disagree with “Grubs are the most consistent turf damaging insect.”
The key word is “consistent.”
Yes, there are many turf damaging insects and when conditions are just right, and populations increase, damage occurs. That was the case in July and August of 2021. Army worm populations reached damaging levels, resulting in battalions of army worms marching across lawns.
But grubs…Grubs are a consistent pest, every year!
White grubs consistently, year over year, cause more turf damage than any other insect.
Here is what you need to know about grubs…
Grubs are white, c-shaped, insects with three sets of legs who feed on all types of turfgrass roots.
What is a grub worm –
Grubs, specially called White Grubs, are white, C-shaped insects with a chestnut-colored head and 3 pairs of legs. Size will range from ¼” to 1 ½” in length depending on age.
They feed on grass roots of all types of turf resulting in yellowing, wilting turf, dead patches, and when left unchecked they will destroy the grass roots to the point that your lawn can be rolled up like it is a piece of carpet.
Signs you have a grub problem -
Early indications of grub damage may include patchy areas of wilting, discolored or stressed turf resembling drought stress.
As the grubs continue to destroy roots, the effected patches expand outward into irregular shaped patches of dying turf.
If you have areas that are wilting, discolored, stressed or dying, it could be grubs, our most consistent turf damaging insect.
Often grubs will start out centralized in an area, but will spread throughout an entire lawn when left untreated.
An indication you have white grubs (often before you have any idea you have a grub problem) is damage caused by armadillos, skunks, possums, and raccoons foraging for grubs. If your home is near wooded or native areas, damage from animals digging for grubs is more common.
Animals foraging for grubs will destroy your lawn in just one night. If you have experienced this, annual preventative grub control treatments should be a part of your routine maintenance plan.
The first step in confirming if you have a grub problem is to check your irrigation for proper coverage. Place a Hall | Stewart Water Gauge or any container in the area showing signs of wilting, run your system through a cycle to see if the area is receiving sufficient moisture.
The next step is to dig up small sections on the edge of the dying grass to see if grubs are present.
The third step is to pull on the grass to see if it comes up easily with few roots.
If you can pull up the grass in the damaged area easily, as if there are no roots hold the turf down, then grubs have been feeding on the grass roots.
If the stressed area is receiving water,
if you find grubs when you dig around the edges of the area,
if you can easily pull the turf up,
treatment is required.
If you find an occasional grub, it is common to find a grub, it does not mean you have a grub problem or that treatment is needed.
In a healthy turf, 5 to 10 grubs per square foot is considered the threshold above which damage will occur.
The grub life cycle -
White grubs complete their life cycle of egg, larva, pupa and adult in one year.
The June bug (beetle), the adult form of the grub worm, emerges in late May to early July. The beetles, attracted to outdoor lights and light from windows, are mostly active in the night. After mating, females burrow into the soil and lay about 50 eggs.
The adult form of the White Grub worm is the June Bug. June Bugs lay eggs in July which become White Grubs in August.
Two to three weeks later the larvae hatch and start feeding first on organic matter, later moving to grass roots.
Grubs go through three stages as they grow. In each stage, their size and appetite grow exponentially.
Stage 1 - Late summer through the fall, grubs are small and feeding near the soil surface. During this phase grubs grow rapidly, feed heavily, and are fully grown by early September.
Stage 2 - During the winter, grubs move deeper into the soil and are mostly dormant.
Stage 3 - In the spring, grubs begin moving closer to the soil surface. As soil temperatures warm, the full-grown grub returns to heavy feeding and can be very destructive.
In late May and early June, the larvae return to adulthood as the June beetle starts the cycle all over again.
Because the June beetle is attracted to light, eggs are commonly laid near outdoor lights.
If you live near a neighborhood streetlight or leave your outdoor lights on at night, you are more likely to see heavier populations of June beetles and consequently a higher probability of grub damage.
Control
There are two methods for controlling white grubs: Preventive and Curative.
Preventive applications of insecticides are systemic in nature. Preventive insecticides are absorbed by the turfgrass roots. As grubs feed on treated roots, they consume a lethal dose of the insecticide. Preventive applications are best applied April through early summer.
Curative applications of insecticides are applied in August through the fall. Curative applications control the insect by making contact with the insect. Contact insecticides are most effective when the grubs are small and feeding near the surface in the late summer and early fall.
There are two approaches to grub control:
Approach 1 – Preventive Plan. If you have a history of grub damage, have outdoor lighting, have experienced the destruction of animals foraging for grubs, preventive applications of grub control should be a part of your normal maintenance program.
Approach 2 – Wait and See. Inspection of your lawn on a regular basis is the key to this approach. If you see areas of wilting, yellowing, or dying turf, check the area by first making sure the area is not just dry, then dig around the area to see if grubs are present, then tug on the turf to see if it comes up easily. Follow up with a curative insecticide if you find grubs are the cause of the stress you are witnessing.
Note: When making a grub treatment, watering is important. If soil is dry, watering (1/4-1/2”) before the application will encourage grubs to come closer to the surface. After the insecticide is applied, water is required to move the insecticide into the soil where the grubs are feeding. It is best to water within 2-3 days as the insecticide will not be active until it is watered into the soil.
Hall | Stewart wants you to help you have your best lawn!
Control of grubs is an important step in having your best lawn!
If you need help determining if you have a grub problem or if you have had grub problems in the past, we would be glad to help.
Simply call (405)367-3873 or reply to this email.
Lorne Hall
Hall | Stewart Lawn + Landscape
(405)367-3873