HELPFUL HINTS HELPFUL HINTS
HELPFUL HINTS
FROM THE LAWN INSTITUTE FROM THE LAWN INSTITUTE
FROM THE LAWN INSTITUTE WHITE GRUBS
hatch or in the first few weeks of development. Later stages can be more difficult to control, and significant damage may have already occurred. If left uncontrolled, white grubs will continue to feed throughout the summer months and cause further damage.
To confirm that white grubs are the reason for yellowing or dying patches of grass, dig up some small sections on the edge of dying grass. If the grass readily pulls up, with few roots, and grubs are apparent in the soil (5 to 10 grubs or more per square foot), then treatment may be justified.
White grubs are the larval stage of scarab beetles. Tere are hundreds of species of scarab beetles but only a few species cause damage to lawn grasses. Tey vary by region but most often include May/June beetles, Masked chafers, and Japanese beetles.
White grubs feed on the roots and other below ground portions of all grasses. Visible damage includes irregularly shaped patches of dead grass that may resemble symptoms of drought-stress. In severe cases, damaged grass can often be rolled up like a carpet.
As with the successful management of many species of insect pests, a critical component of effective white grub management is prevention.
White grubs go through complete metamorphosis, which is a four-part life cycle including egg, larval (grub stage), pupal, and adult phases.
Te mating flights of these beetles take place at night, and male beetles especially are attracted in large numbers to outdoor lights and lighted windows. After mating, the females burrow into the soil to lay a clutch of eggs which hatch and become grubs. Te grub stage molts (sheds its old exoskeleton), and as the larva progresses through the three instars, its size and appetite grow exponentially.
White grubs generally cease feeding in the fall and remain mostly dormant throughout the winter and into the spring months. In the spring they move closer to the soil surface and begin feeding for a brief period of time. Te ideal treatment time for white grubs is around the time grubs
For more information on lawn care and helpful “How to” tips, visit The Lawn Institute at:
www.TheLawnInstitute.org.
TPI Turf News May/June 2021
For more information on lawn care and helpful “How to” tips, visit The Lawn Institute at:
www.TheLawnInstitute.org.
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Effective preventative treatments include products containing the insecticide active ingredients chlorantraniliprole, clothianidin, cyantraniliprole, imidacloprid, or thiamethoxam. Tere are also combination products available that contain bifenthrin mixed with either clothianidin or imidacloprid that are labeled for preventative treatment. Although these treatments can also provide some control after damage appears, they are most effective if applied early. Tere are also organic options often comprised of insect-killing nematodes, but they tend to be more difficult and expensive to use. Te ground should be kept moist prior to application of nematodes, and at least one-half inch of water applied immediately after nematodes are sprayed.
For any type of treatment, irrigation is essential. Pre- treatment irrigation encourages white grubs to come closer to the surface, and helps prepare the soil for better insecticide (or nematode) penetration while post-treatment irrigation moves it through the thatch into the root zone where grubs feed. Grubs are seasonal and often sporadic which makes scouting an essential tool for control of this bothersome pest.
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