Lawn Damaging Insects Including Grubs
It has been estimated that the average insect population per square mile is equal to the total human population of the world. Of course, only a few insects cause significant damage to lawns.
Lawn damaging insects can be divided into two main categories, surface feeding insects and sub-surface feeding insects. Examples of surface feeding insects are the Armyworm, Cutworm, Sod Webworm, Chinchbug and Greenbug Aphid. Subsurface feeding insects include Billbug Grubs and the various White Grubs.
Surface feeding insects destroy grass by chewing blades or sucking plant juices. Sub-surface insects destroy lawns by feeding on the roots of the grass plants. The damage caused can show up in many ways: Feeding may weaken the plants and cause an unthrifty appearance. Patches of grass may be consumed giving the lawn a patchy, uneven appearance, or areas of the lawn may actually turn yellow, brown or die.
How can you tell if your lawn has an insect problem?
Lawn insects are not very easy to see. When you are out on your lawn you should be looking for several indicators that will alert you to a possible problem. Some of the common indicators of insect activity are:
- Large flocks of birds on the lawn pecking holes in the grass as they search for insects.
- Small moths are seen flying around the lawn during the evening hours.
- Patches of grass chewed off right at the soil level.
- Lawn can be rolled back like a carpet since the roots have been chewed off.
- Skunks and raccoons tear and destroy existing lawn searching for grubs.
Can insects be kept out of the lawn?
Grass plants can stand a few insects chewing away on them and still perform very well. It is when insect populations grow and the grass is stressed by heat or drought that the plant becomes weak and dies. Reducing stress on the grass plant, by mowing and watering properly, will always be the answer to minimizing insect problems. When done correctly the grass will be healthier, which leads to greater tolerance or injury and the ability of the plant to recover from minor damage.
Plant breeders have begun to develop grasses with improved insect resistance. These grasses have endophytic fungi that live inside the plant making them distasteful to the insect. The insect either dies or moves on to another lawn. These grass types can be added to existing lawns by overseeding in the fall.
If between our regular visits to your lawn, you notice possible indications of insect activity, give your leisure lawn® technician a call. Your technician will visit your lawn and complete a thorough inspection, looking closely for insect activity that may cause injury to your lawn.
Occasionally, it becomes necessary to use plant protection products to reduce or prevent damage. When your lawn technician discovers signs of damage, the first step is to identify the insect causing damage. He will then outline for you the necessary course of action to reduce the damaging insect population and prevent further damage.
More information on grubs? (Grubs=Beetles=Grubs)
There are 3 species of white grubs that feed on your lawn: Japanese Beetle, Northern Masked Chafer and Junebug Beetle. All of these grubs have similar life cycles and are the larval stage of the beetles. The Japanese beetle is an imported pest and is slowly working its way west. The other two beetles/grubs are native.
The life cycle of a beetle/grub is completed in one year's time. Eggs are laid in soft soil during the summer. The eggs hatch into small larvae. The larvae begin feeding on the grass roots, depriving the grass plants of adequate moisture. Your lawn turns brown and slowly dies. The grass can be picked up like a carpet. These small grubs are voracious feeders and go through 3 or 4 changes in body size through the fall. The last stage burrows deeper in the soil and waits through the winter for the soil to warm in the spring. The large grub burrows toward the surface and lightly feeds and then pupates. The pupal stage transforms the grub into a beetle. In the late spring or early summer the adult beetle emerges and begins feeding and mating. ------ And the cycle continues.
What does all that mean to the lawn owner?
- First, beetles need moisture to lay eggs. And, eggs need moisture to hatch,
- The female will lay her eggs in a site that has good food for the grubs to survive.
- The grubs eat the roots of grass plants, but not all of the roots and the lawn slowly dies.
- The Japanese beetle is the most aggressive feeder and seems to be attracted to purple foliage like purple plum and Japanese maple. Other favorites are Lindens, Birches, Grapes, Roses and Tall Shrubs.
- The small grubs are easier to kill than the large grubs.
For these reasons grub attacks are as unpredictable as a lightning strike. However, well watered and thick lawns are good candidates for an infestation. Heavy rains in the summer, what we call "frog stranglers", make it possible for grubs to appear anywhere.
Grubs can be prevented with the application of a systemic insecticide in the summer. We generally wait until mid-June to begin the applications, that way the material is at full potential when the grubs are small and feeding voraciously. We stop making preventative applications by mid-August and rely on curative applications to stop an infestation. We would recommend a preventative application in June of the following year. We can not kill them all, but we can reduce the population to the point where there is no discernible damage. That is at about 3 to 4 grubs per square foot. You will always find grubs along edges and in planting beds, but they should be no cause for alarm.
Some myths to be discussed: One, moles indicate grubs are present. Well, yes and no. Moles are insectivores and eighty percent (80%) of a mole's diet is earth worms (pin sized up to and including "fishing" worms). Grubs are like pepperoni on an earth worm pizza for a mole. Raccoons and skunks tear up lawn in the late summer and fall trying to get at the big, fat grubs to prepare for winter hibernation. I think the grubs give off an odor and are big enough to warrant the effort for a raccoon or skunk to dig it up.
Two, milky spore is a natural way to control grubs. Yes, but, it only controls Japanese beetle grubs and not Northern Masked Chafer and Junebug beetle grubs. It takes several years for the spore to get established in your lawn. Meanwhile the grubs continue to play havoc with your lawn. You may well have to use an insecticide and the insecticide will kill the milky spore. Catch 22.
Bottom line is - if you suspect grubs - give us a call and we will give you a plan to control them. DO NOT PANIC and start ripping the brown grass clumps up!! Believe it or not, a lot of the brown grass can re-root and recover in place. All you need to do is start a program of watering the brown area for 30 minutes daily for the next month or so. We can stop the grub infestation. After things get under control, areas lost to the grubs can be core aerated and over-seeded in the early fall.