A. The white grub worm is the larval or immature stage of the adult June beetle (also known as the June bug). There are more than 100 species of June beetles in Texas. Only a few species of these beetles cause damage to turf grass, ornamentals and flowers.
The life cycle of the June beetle is a one year cycle and the larval stage of this cycle is the time when the damage occurs. During late spring or summer, the adult beetles emerge from the soil to mate. The females return to the soil to lay her eggs (approximately 30-40). After about two weeks, the eggs hatch into small white grub worms. They begin feeding on the roots of turfgrass and other plants. During the next spring, the pupal stage develops and in early June the cycle begins again, hence the name June beetles.
The larval stage of the June beetle has three pairs of legs and it has a creamy white, C-shaped body. A larvae passes through three stages of growth occurring about every three weeks. These stages are called in-stars. The third in-star is the most responsible for damage due to their large size and their huge appetites.
The next phase of the June beetle's life is the pupal stage. This is the stage that follows the third in-star and is the stage in which the grub worm transforms or metamorphoses into an adult beetle. The pupal stage does not consume food and does not move through the soil at all.
Although heavy populations of grub worms can result in brown spots developing in an infested lawn, not all brown spots in lawns are caused by grub worms. Lack of water and some turfgrass diseases also cause dead spots. To be sure, try tugging at the grass in the brown area. If the grass pulls out with no roots attached, or if you can lift entire sections of turf from the soil (as if pulling up a carpet), you may have grubs and may want to apply an insecticide. The best time to treat grub worms in the Texas Upper Gulf Coast is in mid-July to early August when the young larva are feeding. However, this time will vary according to your location in Texas.
The insecticides chlorpyrifos (commonly known as Dursban) and diazinon are no longer available for sale; however, you may use either of these products if you have them on-hand. You can effectively control the white grub worm with any available insecticide product containing pyrethrins, permethrin, or imidacloprid. A reduction in grub populations can be observed within two to three weeks following a properly timed treatment. Properly timed and applied chemical treatments should be effective with only one application. Irrigating the soil prior to insecticide application, particularly when the soils are dry, can improve the effectiveness of insecticides.
Remember, when using an insecticide or any other pesticide, always read and follow all label directions carefullyĖitís the law and itís for your well-being. Moreover, overuse or misuse of insecticides can cause pollution and lead to poor control of the grubs.
Always read and follow all directions provided on the label of a pesticide before using. Information given above is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Texas Cooperative Extension is implied.
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