what is a grub worm

Scientific Name: Varies

Order: Coleoptera

Description: Adult beetles, commonly referred to as May beetles or Junebugs are ½ to 5/8 inches long, and reddish brown. White grubs are "C"-shaped larvae, up to 1 inch long, with cream-colored bodies and brown head capsules. They have three pairs of legs, one on each of the first three segments behind the head.

There are more than 100 species of scarab beetles from several genera (e.g. Cyclocephala, Phyllophaga and others) in Texas that are considered to be white grubs, May beetles and Junebugs. However, the most common is Phyllophaga crinita. Their biologies are similar, but species differ in distribution, habitat preference, length of life cycle and seasonal occurrence. Other common species include the southern masked chafer, Cyclocephala immaculata (Oliver), and the green June beetle, Cotinis nitida (Linnaeus). One notable member of the family Scarabaeidae, the Japanese beetle, Popillia japonica, introduced into the northeastern United States and migrating west and south, has not been detected in Texas to date.

Life Cycle: Adults begin to emerge in spring. During adult flights large numbers of beetles can be attracted to lights. Peak flights occur in mid to late June in central Texas. Females, less attracted to lights, tunnel 2 to 5 inches into the soil and deposit eggs. In 3 to 4 weeks, small grubs (larvae) hatch from eggs and develop through three stages (instars), with the first two stages lasting about 3 weeks. The last larval stage remains in the soil from the fall through spring. In spring and early summer, white grubs pupate 3 to 6 inches deep in the soil. Adults emerge from pupae in about 3 weeks. There is one generation per year, but in north Texas, development may take two years.

Habitat, Food Source(s), Damage: Mouthparts are for chewing. Phyllophaga crinita is common in Texas turfgrass, particularly bermudagrass, St. Augustinegrass and tall fescue. Feeding of large numbers of grubs causes lawns to turn yellow and die. Severely damaged grass can be "rolled up" like a carpet. Grubs also feed on the roots of weeds, vegetable transplants and ornamental plants. In agriculture, they are important pests of forage, corn, sorghum and sugarcane. Most severe injury to plants is caused by large (third stage or instar) grubs feeding on roots in the fall and spring. White grubs are frequently encountered tilling garden soil or by sifting through soil underneath damaged turfgrass. Adults can be abundant around lights in the spring of the year.

Pest Status: Larval stages eat roots of grasses, vegetable and ornamental plants; Adults can be a nuisance around lights at night in early summer; medically harmless.

Dealing with White Grubs in Lawns

what is a grub worm

Peeling back the grass has revealed a high population of white grubs.

White grubs are the most serious and destructive lawn insect pest in Illinois. While not all lawns will get grubs and the extent of grub damage varies from year to year, there are some important points to consider concerning managing grubs in lawns. Grubs are white in color, with a characteristic "C" shape body when found in the soil feeding on lawn roots. Grubs are the larval stage of beetles.

The most common grub species in our area is the annual white grub, of which the adult is a tan chafer beetle. Eggs are laid in the soil in mid-summer, primarily on well-watered lawns in full sun, often near pavement. Damage from annual white grubs typically starts in mid August and may continue until early October. Other species may damage lawns in northern Illinois, but usually are not as common as annual white grub. Monitoring and control of these species is the same as for annual white grub. The true white grub (May or June beetle), for example, typically has a 3-year life cycle, meaning it could potentially damage lawns throughout the season. Japanese beetle grubs can also occur in northern Illinois, with timing very similar to annual white grub. Adult Japanese beetles are serious defoliators of many ornamental plants.

what is a grub worm

Racoons looking for grubs have significantly damaged this lawn.

Since grubs feed on the roots of lawn grasses, damage will appear as browning of the lawn. Consider that this also could be due to problems such as drought, poor soil, and diseases. However, grubs are easy to find by lifting sod in damaged areas and checking the root zone for the whitish grubs. Don't treat for grubs that don't exist! Skunks and raccoons may tear up lawns in search of grubs, even when grub numbers are relatively low. Typically a population of about 12 grubs per square foot can cause lawn damage that requires control; whereas lower populations may not damage the grass, they may attract skunks and raccoons.

Lawns showing damage from grubs may be treated with an insecticide. Insecticides available for homeowners include Imidacloprid (various trade names), chlorantranilprole (GrubEX),triclorfon (various trade names) for control of white grubs. Heterorhabditis bacteriophora nematode is an example of an alternative product for white grub control that is available.

For all products, read and follow all label directions, then apply to damaged areas. Water the insecticide into the soil immediately. If treating a large area, stop after a portion has been treated and water the material in, then complete the rest of the lawn area needing treatment. Only treat in and around affected areas; grubs may only be in a small part of the lawn. Imidacloprid is suggested to be applied before grub damage appears. An example of a way to use this product would be to apply in July to irrigated lawns that are surrounded by dry lawns, especially when adult beetle flight is high in areas with a history of grub damage.

Spring treatment for annual white grub is not suggested since the grubs feed for a short period of time in spring and are reaching maturity, thus are not controlled easily. In addition, turfgrasses are actively growing at that time so usually don’t show damage.