Grub Treatment and Prevention

Grub Overview

The term “grub” refers to the larvae of various species of scarab beetles. They have soft, wrinkled, C-shaped bodies. The most common offenders are the European chafer, June beetle, and Japanese beetle. See the below chart for more details on these species. While these are the most common, there are many other potentially damaging grubs, such as masked chafers, oriental beetles, green June beetles, Asiatic garden beetles, black turfgrass ataenius, and May/June beetles (phyllophaga species). Female beetles can lay up to 50 eggs, which hatch below the turf surface and feed on the roots.

How to Treat Infestations

Apply preventative synthetic compounds (like Merit, Mach 2, Aloft, Arena, and Acelepryn) between late May- mid August. These control products are highly effective against young grubs after the eggs hatch.

Check for white grubs by pulling back turf at least 3 inches deep and counting grubs per square foot. A few grubs are no reason for concern.

Pro Tip: If there are more than 5 grubs per square foot in dry turf or 15+ in irrigated turf, expect and watch for damage over the next four weeks.

Most damage occurs in the spring and fall when grubs feed near the surface. You’re unlikely to see damage if preventative products were applied from May-August. Japanese beetle damage is unlikely to occur in irrigated areas.

Skunks will tear up turf to feed in the grub hot spots. Pull samples from damaged areas; patches of dead turf tend to be larger and grow more in September through October. Grub-injured turf dies when it becomes very dry. Damage can be minimized with the correct irrigation (deeply but infrequently).

You can spot treat heavily infested and damaged areas with Dylox or Sevin during the fall season. Granular applications are more stable but require watering in with a half inch of irrigation before becoming effective. Spray applications will not work unless watered in immediately after application. Check sites three weeks later to ensure efficacy.

Use a species identification guide (like Ohio State University’s guide) to help you decide the best control method. Apply insecticide before reseeding, as grubs will eat the seed as well as the new grass roots. Parasitic nematodes can be used as a control option, but this is expensive, and efficacy varies.

Pro Tip: Use your golf course map to mark affected areas to use as a roadmap for next year’s treatment plan; this way you’ll know where to apply preventative compounds.

Next spring, you may find dead patches of turf. If this occurs, watch for the first signs of grub damage, sample for grubs, then treat the hard-hit spots with Dylox or Sevin. Merit, Mach 2, and Acelepryn will not kill grubs when applied in fall or spring.

Prevention

Prevention is key to golf course health, especially in pest management. Well-watered turf will have more roots and is stronger against damage. Water deeply but infrequently to avoid attracting grub eggs to hatch. Aerating and fertilizing can also help turf resistance.

Synthetic pesticides (neonicotinoids) should be applied when female beetles lay eggs, before larvae appears for best efficacy. It’s impossible to judge grub densities in the egg stage before application, so apply these as insurance for turf health. Most grubs are susceptible to the synthetic insecticides, and often have similar life cycles, so superintendents can attack multiple species at once.

It’s best to attack these species together in early summer. Timing is important: if you can see damage, it’s usually too late to treat. Damage can look like dead grass and animals digging up turf for food.

Larvae is difficult to control in the fall, as they start to burrow into the soil for the winter. This changes control tactics as they stop feeding and many insecticides need to be eaten to be effective. Switch to contact insecticides like Dylox (trichlorfon) during this time.

Follow all manufacturer recommendations on timing and application. Golf courses deal with many pests, so identifying white grub infestations and recognizing species to study its lifecycle can help aid future efforts. Develop a scouting program to document problems before they become severe and you need to apply pesticides.

There’s often an interaction between pest lifecycles and weather patterns. If the summer is dry, fewer eggs will hatch since they need to retain moisture. If it’s an especially rainy season, you’ll see less damage because the turf has strong, healthy roots that can withstand more feeding. Less healthy lawns will succumb to damage more quickly.

Best Practices

Keep turf healthy and well maintained, as healthier turf can support a higher grub population. Support turf with proper mowing, fertilization, irrigation, and thatch management. Ensure the turf species is well adapted to its specific site use. Identify the main pest species and locate hot spots. Determine when adults fly, so you know when to act. Use longer term insecticide materials in hot spots and historical trouble areas to avoid repeat grub infestations.

Visit SiteOne for Help

Visit your local branch or SiteOne.com/PestManagement for supplies for the job. If you have questions or need help, associates will assist you. Visit our learn section for more educational agronomic information.