Many of us, at one time or another, have battled grubs in the lawn. The grub is the larvae stage of a variety of beetles. Japanese Beetle, European Chafer and Junebug are the most common three. European Chafer is the worst one for destroying lawns in our area.
| Damage and Identification |
Grubs feed on grass roots causing your lawn to die. The key symptom of grub invasion is irregular dead patches which will lift up easily if tugged on . These patches have had the roots severed and there is nothing to anchor the sod in place. The lawn may also have patches that have been burrowed in or been up-turned by moles, skunks or raccoons feeding on them. The highest concentration of grubs will be found in dead turf bordering green areas. The grub is 'C' shaped with a brown head, white body and six legs on its upper half.
| Life Cycle |
The grub's life-cycle is very simple. The grub feeds on grass roots from mid-March to mid-May, and then develops into its pupal form. The adult beetle then emerges in mid-June, mates over a two week span and retreats back into the soil to lay its eggs. The grubs hatch and begin to feed in late July to August. The grubs will burrow below the frost line in the fall and stop feeding but if there is a thaw, they will resume feeding at any time, even during the winter. The grubs will continue to feed in the spring, constantly growing larger.
| Control |
The fall (mid-August to September) is actually the best time to apply chemical control as the larvae have just hatched and can be killed quickly due to their small size. A certain percentage of chemical must be ingested in relation to body mass, therefore, the smaller the grub the less the amount needed to kill it. They will not die with their first taste. It can take up to two or three weeks. If you don't notice the problem in the fall then you must recognize the problem and apply in the spring. If you're going to apply in the spring, do so around mid-March to mid-April as larvae are feeding ravenously.
Certain conditions can cause unsuccessful control of the grub. Excessive thatch build-up will absorb and hold the chemical rather than allowing it to penetrate to the grub zone. Hot and dry conditions, in late July or early August, prevent successful mortality rate also because the grubs will move to cooler soil below and they won't be feeding. It is necessary to soak your lawn previous to application as this will allow the chemical to be dispersed throughout the soil more easily. Watering in after application is necessary to increase success because the chemical will remain on grass blades, resulting, in a mortality rate that may only be approximately 50% of what it should have been. If you are spraying in the fall, a spring treatment may be necessary as all the grubs may not have been killed the year before.
Beneficial nematodes are a natural control option. These microscopic "worms" actively seek out their prey. They are specific to insects and will not harm any other organisms. All vertebrates are completely resistant to nematodes, as are plants, earthworms and helpful insects such as bees and ladybugs.
The best conditions for nematodes are moist soil (also ideal conditions for plant growth), and they requires no special treatment once applied. The formulation is so fine that when mixed with water it can be sprayed through most sprayer nozzles. However, fine filters should be removed from nozzles to avoid trauma to the nematodes. This product is also compatible with most chemical and biological insecticides.
Garden Tip: When a lawn is well maintained, well watered and well fertilized, there may be grub problem
