The Green Thumb
Many gardeners do not realize that sub-soil, there is a world teeming with life. Bacteria, fungi, insects and animals call the cool organic earth home. One such highly recognizable -- yet misunderstood -- insect is the grub. It is hard to dig a hole without uncovering at least one of these milky white, c-shaped larvae. Here is what you need to know about grubs and how to stop them from causing harm in your lawn or flowerbed.
White grubs are the larva of scarab beetles such as May beetles (sometimes called June bugs), "masked" chafers and black turfgrass ataenius. May beetles and chafer beetles are commonly seen flying at night, when they swarm around lights on the street or homes. While the beetles do not damage turf, their grubs can be destructive.
Most May beetles have a three-year life cycle. During the first year, beetles mate and deposit eggs in the soil during late spring and early summer. Larvae develop slowly during the remainder of the summer and into the fall. Although they feed on grass roots, they are incapable of causing serious damage because of their small size that first year. As soil temperatures cool during the fall, larvae cease feeding and move deeper under ground to spend the winter. As soil temperatures warm again the following spring, larvae move back up to feed on grass roots. By late summer, mature grubs are capable of causing extensive damage to lawns. This is when most homeowners notice the physical damage of dead patches. And this is when most homeowners want to control the grubs. But it is not the best time, nor is spring.
Because the larvae are starting to return to the soil surface to feed, and because gardeners are starting to dig more to plant spring plants, and because there are many thinned or dead patches in the yard, gardeners are blaming grubs for their problems and want to control them now.
Grub control actually should begin in July. Mark your calendar to apply a grub preventative on your lawn the first half of July.
Preventatives are normally used on areas that have had a history of grub problems. Traditional grub insecticides such as Dylox are normally applied in late July after the grubs are present or as a rescue treatment once damage is seen. Products that contain Merit (imidacloprid) or Mach 2 (halofenozide) are considered grub preventers. Actually, neither product prevents grubs, but rather they kill grubs when they are quite small, and long before they cause damage. Merit and Mach 2 are safer to use around pets and humans than other grub killers.
Remember, all grub products must be watered in before they are activated.
-- Bruce Chladny lives in Eudora. He is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him from 8 a.m. to 5 p.m. weekdays at 843-7058.