Lawn Grubs

Grub out Lawn Grubs

American Lawngrubs



There are a number species that may infest American yards. These include May & June Beetles, Northern & Southern Masked Chafers, Bluegrass & Denver Billbugs,  Japanese Beetles and White Grubs. We will have a look at all these pests and show you when to be aware of the most likely time of year that each species will be more prominent in your grass.



May and June Beetles.



June Beetle picture taken by pizzodisevo.

As the name suggests the adult beetles will show up in around May and june and then start to lay their eggs in your grass. The new grubs re not usually such a problem unless there is a large concentration of them. Even then, if your grass is in excellent condition it may withstand an attack without showing too much stress in the form of bare patches. Be warned though that large infestations may bring predators that can dig up your grass to feed on the grubs. The worst time for these species is in the second year of their three year life cycle when they are much larger and just a few grubs per square foot can cause visible damage to the lawn. Between feeding seasons they will dig down below the layer that frost will get to in order to stay alive.


Japanese Beetle


Adult Japanese Beetle – Photo by abbydonkrafts

Unfortunately Japanese Beetles can be a problem in the adult phase as well as when a grub and so we should be particularly alert for them as they will eat flowers and leaves of  crabapple, rose, grapes, beans and other plants grown in our yards. Traps for the adults are thought generally only to be really recommended for showing how bad the problem is. These pests having quite noticeable metallic and bright coloration will lay their eggs in mid to late May with the bulk of them being laid before the end of July. You may be fortunate if you have a dry spell as the young larvae are not very tolerant of soil that is dry. Insecticides are probably best used in early summer when the eggs begin to hatch.




Masked Chafers


Picture by dendroica cerulea.

The adult beetles fly n and start laying eggs during june and can go on until mid to late August depending on your location. Once hatched the larvae will start to feed on the roots of your grass, continuing until there is a likelihood of frost with the worst damage occurring from late Summer into early Fall. Once again,location and weather will determine when the grubs stop feeding to go down below the likely depth frost will attain for the winter months. Should your grass be very healthy and vigorous, it will resist these grubs even in reasonably large numbers.



These animals are actually weevils and they can sometimes be seen when away from foliage on our driveways and sidewalks in Spring and Late Summer. The females will cut small holes in plant stems in order to lay their eggs inside. The grubs usually have a brown head with the rest of them being white or cream. The first real damage is caused by the younger grubs. They will grow to be a third to half an inch long. The affected grass is easily detached from the soil as the younger grubs will have attacked the area of the plant’s crown and killed it. The root area and lower crown are eaten by the older Billbug larvae. These grubs will often attack new sod lawns and are quite common in all new lawns. The infestations are often more severe near to protective areas such as evergreens. For best effect with insecticides it is recommended to apply in early May just prior to the adults laying their eggs. Spraying later will not do so much good as the young will be inside your plants and more difficult to get at. In some areas you may get better results by spraying for Denver Billbugs in early June and remember that spraying can often be more effective than more solid products. Sprays should be used when there is a greater chance that they will linger on the foliage longer and this usually means dry weather is forecast. There are natural predators such as hunting wasps, birds and even fungal diseases that will help but one of the better ones is the use of parasitic nematodes that can often be bought locally or may be sent by mail order companies.



There are a number of different insect species whose young are what we generally call lawn grubs. This means that there are different “best times’ to try and kill them off. Some species are best dealt with at the adult stage and others when the larvae are close to the surface of the lawn feeding. Neither chemicals nor introduced parasites will be very effective when the grubs are deeper in the soil because of the physical barrier caused by that dirt. Some chemicals will last longer than others depending on what they are and when they are applied. Nematodes just may outlast all chemicals as they will be carried by the dying grubs and can even live on in the soil waiting for another host to come along.

ALWAYS read and comply with the instructions for your chosen method of lawngrub control.


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