Lawn Grubs and Grub Control
The largest grub is the green June beetle grub. At maturity it has a ½ wide body and is about 2 inches long. May/June beetle and Japanese beetle grubs are approximately a half-inch shorter measuring 1 1/2 inches long. Masked schafers are much smaller at approximately ½ inch long, while black turfgrass ataenius are the smallest at only ¼ inch when fully grown. If grub controls are necessary, it should be applied before any damage occurs. Fast acting grub killing products are available if damage is already occurring. The good thing is that healthy grass can easily sustain and repair damage from a low number of grubs. Visible damage occurs as lawn grubs feed on the grass roots faster than the grass’s ability to replace them. The greatest damage will usually be in the last stages of grub growth as lawn grubs reach their maximum size. Since the life cycles of the various species of lawn grubs are known, the damage they do and the time of year that damage will likely occur is predictable. May/June BeetleThree year Life Cycle of June Beetle (May/June Beetle)The larva of the May/June beetles, also called May or June bugs, are white c-shade grubs that have a three year life cycle. Noticeable damage to the turf doesn’t occur until late in the second year. For the best control, a basic knowledge of life cycles is important. First Year Eggs are laid in the soil during the flight stage of June beetles. The eggs hatch and the small larva begin feeding on grass roots. The insects are so small at this stage that there is no visible damage to the grass. By the end of summer these lawn grubs are still about ¼ inch long. As the soil cools in the fall, the insects begin to move deeper into the soil and over-winter below the frost line. Second Year In spring as the soil warms, the small grubs will emerge from dormancy and begin feeding. Grubs will feed for up to six months and will obtain their full size by the end of summer. It is during the summer of the second year that the majority of damage can be seen. In the fall as soil temperatures begin to cool, the grubs again burrow deeper into the soil in preparation for winter. Third Year
At this point the cycle repeats itself as the adults mate, lay eggs in the soil and die. The adults fly only at night and remain buried in the soil during the day. You have probably seen them flying around the porch light or flying into screen doors. Grub Damage The first signs of damage will be seen in late July or August. Damage begins as a thinning of the grass. From there it progresses to patches of grass that will quickly wilt and die. It will often occur quickly over a period of several days. Once the grass is severely damaged, it will need to be replanted or reseeded at the appropriate time for your specific grass type. Weeds will often encroach in the area taking advantage of the weakness in the turf. It should be noted, however, healthy grass is able to withstand up to 5 grubs per square foot. It is when they exceed that margin that damage really begins to show. Once the adult beetle emerges from the soil, the life of the beetle is short lived. You can probably count on having the same problems again in the following years unless action is taken to break the cycle. Green June Beetle The green June beetle grub and winged adults are slightly larger in size than the May/June Beetle although the lawn grubs look similar. They have a couple different habits that make them stand out from their grub cousins. How the Green June Beetle Larva Differ The first major difference is its feeding habits. The green June bug larva feeds primarily on decaying soil organic matter and will only occasionally feed on grass roots. The problem is more serious in pastures than it is in lawns. Winged adults feed on fruit, but prefers decaying fruit if available. It can be especially damaging to peaches. The second difference is that the grub comes to the surface at night and then crawls on its back with its feet in the air. No other grub crawls this way. It is not quite as C-shaped as other lawn grubs. The green June beetle larva is more of a problem in field crops and pastures than in home lawns. In lawns, the damage they cause is mainly due to their vast network of tunnels very near the soil surface. Although their tunneling does provide some aeration to the soil, heavy tunneling dries out the roots and can also uproot plants.
Life Cycle of Green June Beetle Green June beetles have a one year life cycle. The female beetle looks for soils rich in organic matter to lay her eggs. Soils with decaying manure, litter, leaves, stray or hay make good prospects for the female beetle. The eggs hatch in about two weeks and the young larva begin moving and feeding in the soil. In the fall, as temperatures begin to drop, the larva will have reached their full size. It over-winters deeper in the soil and becomes active again in the spring. In April and May it will form a small chamber in preparation to pupate. Pupation generally lasts for two to three weeks. After pupation the adult beetle will remain in the soil for a week or two longer. Only then will it emerge as an adult and repeat the cyce. Different locations will have different peak flight times, but it is generally from June to July. Unlike their June bug cousins, Green June beetles fly during the day and burrow into the soil at night. Grub Damage Most of the damage caused by the green June bug is from horizontal tunnels. A few tunnels can actually loosen and aerate the soil, however, when there are a large number of grubs, their tunneling can cause severe damage. Excessive numbers of grubs produce an enormous amount of tunnels. This will lead to a much faster loss of soil moisture and add stress to the grass. In pastures, loosened soil allows cattle to easily pull grass from the ground when feeding. The result can be large patches of dirt where grass once stood. You can find evidence of grub worm activity by looking for exit holes surrounded by a small mound of pulverized soil. Pulverized soil looks like small granules similar to ant hill dirt. Where tunnels are extensive, the ground will be somewhat spongy. Indirect evidence may be small holes where animals have been digging for lawn grubs. Armadillos and skunks are noted for this. Masked Schafer BeetleMasked schafer beetles, also called "annual grubs" have a one year lfe cycle. At first glance, masked Schafer adults are similar in appearance to June beetles, except they are a more golden brown and about half the size. The lawn grubs are white with a brown head, six legs and are c-shaped.Life Cycle of the Masked Schafer Beetle Masked Schafer beetles have one generation per year. In late spring to early summer, winged female adults tunnel into the soil to lay eggs. Eggs hatch a few weeks later and the tiny grubs immediately begin feeding on organic matter and grass roots. By the end of summer, masked Schafer grubs have reached their full size. When numbers exceed 6 to 7 grubs per square foot, severe damage can occur. Damage usually shows by late summer or early fall. As the temperature drops in the fall, the mature grubs will tunnel deeper into the soil in preparation for winter. As spring temperatures rise, the grubs emerge from hibernation. In May they will build an earthen cell in preparation to pupate. Two to three weeks later an adult emerges from the soil and looks for a mate. Like the June beetle, masked schafers fly at night and can be seen buzzing around porch lights, windows or screen doors. Grub Damage Damage occurs when populations of lawn grubs become excessive. Numbers above 6 to 7 grubs per square foot of turf can cause serious damage. Look for damage to occur in August to September. Grass will turn tan or brown in increasing larger patches as the lawn grubs feed.
In more severe cases, the grass will easily pull up from the soil as the roots are being cut. In the worst cases, you can actually lift and roll up the grass like a rug. (Photo courtesy of University of Nebraska Entomology Department. Used by Permission.) Black Turfgrass AteniusBlack Turfgrass Atenius lawn grubs are very small, only ¼ inch long. These small grubs feed on bentgrass, annual bluegrass and Kentucky bluegrass. They are primarily a problem on golf course greens, but will occasionally attack home lawns. Northern states are more affected, due in part because bentgrass and bluegrass are cool season grasses that are more prominent in the cooler areas of the north.Life Cycle of BTA Beetles Adults beetles overwinter in organic debris, loose soil, thatch, or any suitable material. In March or April the adults lay eggs in the soil on bentgrass or bluegrass golf greens and lawns. The eggs hatch in one to two weeks and immediately begin moving into the root zone to feed. In as little as three to five weeks the grubs will move deeper into the soil to pupate. Adult beetles emerge from the soil in late July or August. The adults mate, lay eggs in the soil or thatch and the process begins again. A second generation emerges from the soil in October, but will wait until the following spring to mate. Grub Damage Description Damage begins as small brown patches of thinning and dying grass. The patches enlarge as the grubs feed on fresh roots. Roots will be pruned as deep as one inch into the soil. With a slight tug, clumps of grass can easily be pulled up. In cases of heavy feeding, the grass can actually be rolled up like a rug. Underneath you will find several small C-shaped grubs. A few grubs are not a concern. Extensive damage begins when numbers reach 30 to 40 grubs per square foot range. Factors That Affect Grub Numbers and DamageAdult beetles will look for soil types that have the qualities suited for larva development. If you have had problems with lawn grubs before, you will probably have them again. It means you have the soil type they are looking for. The green June bug is a good example. Since their primary food source is organic matter, lawns with ample amounts of organic matter are prime targets. A few grubs are normal in lawns. It is when grub numbers exceed a certain threshold that damage occurs.You can check for grubs by slicing and lifting a small section of turf. Slice the turf a few inches deep using a knife (careful not to cut yourself) or shovel on three sides and lift up the grass. Grass growing in sunny locations will usually reveal more grubs than grass growing is shaded areas. For egg development, adequate soil moisture is needed. Eggs can’t move around to locate better conditions, so if the soil becomes too dry the beetle eggs dry out and die. Dry conditions can be a natural means of keeping beetle populations under control. If your grass is healthy and you are having a drier than normal spring or summer, you can allow your lawn to remain dry. Be careful, however, your grass will show signs, such as color change, when it is in need of irrigation. Remember, grass is better able to endure periods of drought as long as it was care for properly before the drought occurred. Grass that is maintained at higher levels, watered deeply, but less frequently will develop a deeper root system and develop better drought tolerance. On the other hand, healthy, well water grass can repair damage faster than stressed grass enabling it to endure higher levels of grub activity. Many grasses, such as fescue, have some of the fastest root production rates with proper moisture and fertility levels. In cool season grass, heavy nitrogen applications during spring and summer reduce root growth and increase risk of grub damage. See the section on f Developing a Fertilization Program or information on how to properly fertilize your lawn. Grub Control ProductsThere are several types of grub controls from fast acting grub killer products to slower acting season long insecticides. Newer and more environmentally safe biological products are available. Some of these products are insect specific. Below is a list and description of available lawn grub control products.Quick Kill Products If you are currently experiencing damage from grubs you don't want a product that will begin killing grubs a month after it was applied. Instead, you will need a fast acting lawn grub control product.
Preventitive Lawn Grub Products If you have had damage in previous years and want to treat your lawn before damage occurs you can use a slower acting lawn grub control product. Look for products with the active ingredient:
Red Imported Fire Ants These dangerous ants are found throughout the southern U.S. and will fiercely defend their nests whenever it is disturbed. To the unwary person, dozens of painful stings can occur within seconds. Learn valuable information about these insects and the methods used to control them. Lawn Moles and Voles Moles can be very frustrating to deal with. Some people learn to live with them, but you don't have to. Knowledge is the key to getting rid of moles. Go from Lawn Grubs back to Turf Pests
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Lawn grubs, also called grub worms or white grubs, are actually the larva of scarab beetles. There are a few common species that are known to damage grass. They are the larva of the May/June Beetle, Green June beetle, Japanese Beetle, Masked Schafer Beetle, and the Black Turfgrass Ataenius Beetle. 
During the spring of the third year, once again the lawn grubs move to the soil surface. However, the third year there is only a little feeding since they have already reached their full size. In late summer the grubs encase themselves in an earthen ball and begin pupation. Pupation is usually complete by the end of September. Since temperatures will begin cooling soon, they will remain in the soil until May of the following year when they begin to emerge as winged adults. Depending on the species, they may emerge anytime from May through July. (Photo courtsey of the University of Nebraska Entomology Department. Used by permission)
Note: The adult green May/June beetle is often confused with the Japanese beetle since they both have some green in them. However, when side by side the differences are obvious. While the Japanese beetle grub is almost identical to the May/June Beetle grub, it is important to distinguish between the adults. If you look at the photo, the adult Japanese beetle has a row of white spots on each side of its body and reddish brown wing covers on its back. If you see a Japanese beetle in your area, be sure to report it to your county extension office or Dept. of Conservation. The Japanese beetle is a quarantine insect in most of the states where it is found.
In less severe cases, grass has the appearance of being drought stressed. However, when water is applied, it will usually not help since moisture is not the problem. The weakened grass becomes more susceptible to environmental stresses and weed invasion. 
