Control of any pest problem begins with determining that you actually have the pest you think you do, and this means finding a way to collect them. It helps, also, to understand the habits of white grubs so that you can inspect for them or attempt to control them at a time when you will be most successful. The larvae move up and down in the soil in response to moisture and temperature, and may end up as deep as 2 or 3 feet down, particularly in the northern states where the soil freezes well below the surface. So, if you are trying to sample for the larvae you need to either pick a time of year when the temperature is mild and the soil is moist, at which time the larvae would be most likely to be in the root-zone of the turf, or water the lawn to encourage the larvae to make the trip upward. For white grubs you then can use a sharp tool to cut out a section of the lawn and peel it back to expose the roots. If the conditions are correct for the larvae to be feeding you should be able to see these white grubs very easily. The turf can then be rolled back into place without harming it from the cutting.

One resource you should use in your geographic area is your University Cooperative Extension Service, and you can find their websites quite easily on the internet. The importance of white grubs varies widely across the country, and one of the variables is how many grubs it takes to warrant trying to control them. This is referred to as the "threshold" level for the pest, and for white grubs it would be a count of how many larvae are present in each square foot of the turf. For very sensitive or important turf, such as a golf green, that threshold level might be only 1 larva. But, for hardier turf that does not need to look so manicured the threshold level might be much higher, perhaps 10 grubs per square foot. The meaning here is that an infestation below the threshold level, for your geographic area and turf type, would not warrant going to a huge effort to eliminate the insects. The small amount of damage they would cause would be minimal.

So, stay in touch with your local Extension Service, check their advice on the need for control, and identify the actual presence of the pests. Brown patches on your lawn could be caused by lots of other things besides insects. If you find you do need a control program it would be good advice to contract with a licensed pest management company. These folks have the training to use insecticides correctly, they have the equipment to apply the materials to a large expanse of lawn, and they have access to products that you might not on the retail shelves. These products may require that the user be certified or licensed.

Your home remedies for control could include some non-pesticide options. One material that can be effective on Japanese Beetle larvae, and to some extent on some of the other white grubs, is called Milky Spore. This material is composed of bacteria, apparently native to North America, which feed on beetle larvae, and in areas infested with Japanese Beetles this material likely is available in retail stores. There are also a number of kinds of parasitic flies and wasps that are known to feed on white grubs, but at this time you may not be able to find these commercially. One family of wasps is called the Scoliidae, and releases of this wasp in Hawaii have shown success in reducing populations of the Oriental Beetle there.

So, the take-home lesson here, hopefully, is that white grubs can definitely be a problem for your lawns, but quite often they get blamed for the damage you see when the cause is something else. If you suspect an insect problem you should sample in the proper way to determine if it truly is there, and if so then you need to decide if the level of the pest population is high enough to warrant going to a control program.