Lawn grubs, often called white grubs, are the immature form of various types of scarab beetles, such as Japanese beetles, June “bugs” or the European/Northern/Masked chafers. The size of the grubs can vary on the species and the age of the larva. Residential lawns in the North East are subject to severe and extensive damage from the larval stages of the various species of beetles, “grubs”. The prominent species of grubs here in Massachusetts that cause turf damage are the Japanese beetles and northern masked chafer grubs. Both of these beetles look very similar and share similarities in their life cycles. In order for you to know how to treat grubs and prevent grubs from damaging your lawn, you need to know the grub’s life cycle. Knowing this will help you to be proactive in protecting your lawn when it is most susceptible to their damage and when the right time is to protect your lawn in order to prevent an infestation from occurring.
The Life Cycle of a Grub
The life cycle starts in the spring, the grubs awaken from the winter and begin feeding on the grass roots and other organic matter in the soil. After they feed, the grub becomes a pupa and enters into the pupal stage of its life cycle. This is the inactive and immature form between the larva and the adult stage of the grub’s life, the transitioning period. In the pupal stage the grubs are dormant underneath the lawns surface until they become beetles. In the early to mid-summer the pupal stage comes to an end and the beetles emerge and start feeding on the garden foliage and flowers. This is also when the beetles start to mate and dig back down into the soil to lay their eggs. The beetles mating season lasts about two to three weeks. The eggs stay in the soil until they are ready to hatch. The time eggs hatch depends on multiple variables such as soil moisture and temperature to name a few. But, most times during “normal” summer months the eggs hatch two weeks after being laid, in the mid to late summer. This new generation of grubs will start feeding on your lawn immediately after hatching. This makes fall the peak grub feeding season. Grubs can be found anywhere in your lawn; they could be anywhere from 2 inches deep or they can burrow down to 8 inches deep before the winter arrives and they become dormant again. Most beetles only have a one-year life cycle, but some of the different species can have up to a three-year life cycle.
How Grubs Can Damage Your Lawn
Grubs can cause extensive damage to your lawn for multiple reasons. Either they are feeding on the root system of your turf or the damage can come from other animals digging to feed on the grubs themselves. In the spring as the lawn greens up and you find that your lawn has some areas that are not turning green at all, that could be a sign of damage caused by grubs feeding on that area the previous fall. To check your lawn for grubs you can try lifting up the “dead “area of turf by grabbing a hand full of grass and if it just lifts up and has no roots holding it down you will know grubs have eaten that area. Something else to watch for, that could be a sign that your lawn is being infested with grubs, could be that more birds, skunks, raccoons and/or moles are present and digging in your lawn. That is a sign that they could be trying to dig down to eat the grubs. Another symptom of grubs may come as a surprise to most people, but if you detect a spongy area in your yard and you have a well irrigated healthy lawn it could be an early sign of grubs before the brown areas become present. All of these are signs that your lawn could be suffering from grubs, but you cannot always count on these signs. The animals also eat other surface insects, and different lawn diseases could cause a spongy area and brown patches. The only way for a correct diagnoses of grub damage is to start digging several 1 square foot sections that are 2-6 inches deep. If grubs are present and feeding you will know that your lawn has grubs. But, having some grubs in your lawn is normal and that it is okay. A healthy lawn can easily support a small grub population. An average lawn should have anywhere from 0-5 grubs per cubic foot, and could possibly handle as many as 9 grubs per square foot.
How Can I Prevent Grubs from Damaging My Lawn?
The best way to stay ahead of a grub infestation is to treat the lawn with a Grub Preventative, like we do. It is less expensive and easier than digging several holes in your lawn and counting the grubs. We believe it better to be proactive and incorporate this step in our lawn care program, rather than be reactive after the damage is already done. We recommend a preventative product that will help eliminate grubs over a longer period of time; this product protects your lawn from the grubs that are present at the time of the application as well as those grubs that will hatch during the season and try to feed on the root system of your lawn. Immature grubs are most susceptible to pesticides so for optimum results the grub preventative needs to be applied at the right time of the grub’s life cycle. As mentioned above, it varies year to year depending on the weather, temperature, and when the eggs are ready to hatch. A good turf care company will know this. In most cases we will use a granular product and combine this with your early summer fertilizer application. This preventative should be watered into the lawn 24-48 hours after the application to ensure the product soaks down into the root system, which is the prime feeding grounds for grubs.
We will always advise you to protect your lawn all year round, but if you do not treat your lawn with a grub preventative and it does get infested and damaged by grubs, there are products that will kill existing grubs on contact. These products can be very expensive though and the application/process extensive. The product must be watered in the same days as the application and there is a re-entry restriction that states the area has to be completely dry before re-entry. And not only do you have to treat the lawn to rid it from the grubs, but you also have to repair your lawn from the damage they have done and regrow the grass in the areas that were damaged.
So, instead of waiting for them and their damage to occur, we like to stay one step ahead by providing you with a grub preventative application. We want you to be prepared and to enjoy the seasons we are lucky enough to have. We want you to entertain guests, enjoy your yard with your family, and relax as much as possible outside in your beautiful landscape you work so hard to have.