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Lawn Grubs - Mother Nature's Curse to the Garden

• Have you wondered why your lovely green lawn suddenly goes brown and straw like?
• Are there moths flying over your lawn?
• Maybe the leaves on the grass runners are just disappearing?

The Grub-damaged Lawn
Severe grub damage in a lawn appears as large, irregular sections of brown turf that detach from the soil without effort. Unlike turf damaged by drought or excessive fertilizer, the turf peels away like a carpet being rolled up. For most of the year, however, grubs are out of sight and out of mind. They feed on grass roots in your lawn and are usually noticed only when dead and damaged areas appear.

Know Your Grubs
White grubs are immature scarab beetles (for example, European chafers, Japanese beetles, and Oriental beetles). Although all grubs cause similar damage, the treatment you choose should correspond to the species. Lawn care professionals and homeowners should learn how to identify grubs and can consult with local IPM experts for training. Knowing the species helps you pinpoint effective strategies that will work in your climate.

Got Grubs? Count to 10
How many grubs are too many? Research has shown that only 20 percent of home lawns and golf course fairways require treatment. Here’s a guide to treatment thresholds for European chafers, Japanese beetles, and Oriental beetles, the most common grubs in home lawns. Numbers are based on grubs/sq.ft.

0-5 grubs: rest easy
Fewer than five grubs per square foot is a low population. You don’t need to treat.

6-9 grubs: think about your lawn
Is your grass dense, with a healthy, robust root system? If so, it can probably withstand grub populations of 6-8 per square foot, or more. On the other hand, if animals such as skunks, raccoons, birds, and moles are digging up the turf to feed on the grubs and this bothers you, consider treating highly populated areas.

10 or more: they may cause damage
Ten or more grubs per square foot will likely cause damage, especially if the lawn is otherwise stressed. In most circumstances, you’d be justified treating where populations are this high. Several weeks after treating, sample in a few locations to determine whether treatments were effective.

Compensating for grub damage
Many characteristics of a lawn determine how well grass grows. You can, however, help your lawn to compensate for loss of roots by watering it properly (see lawn maintenance) and reseeding damaged areas.

Treatment in our area is usually between May and August

Treatment Options -

Nematodes
 Insect-attacking nematodes can be applied to control caterpillars or grubs. Each nematode species is effective on a different range of pests. Select the nematode species most effective against the target pest(s).  All nematode species are most effective when applied during the early part of the season for that pest when grubs or caterpillars are active. A second application about 2 weeks after the first increases the likelihood that nematodes will reproduce and provide long-term pest control. Irrigate before and after application. Apply to warm (at least 60°F), moist but not soggy soil. Several irrigations may be needed during the 2 weeks after each application to keep soil moist. Because nematodes are killed by light and heat, apply them in the evening, especially in hot areas

Choosing the correct insecticides
If cultural practices are not enough to prevent damage and a drench test or root inspection indicates treatment is warranted, choose selective, least toxic, IPM-compatible products whenever possible to control pests. The insecticides azadirachtin, pyrethrum (pyrethrins), and imidacloprid are relatively safe products for lawn insect management. Each of these products is effective only on certain pests and all must be properly timed and applied to be effective.