Lawn Grubs

Grub out Lawn Grubs

Japanese Beetle


Japanese beetle is one of the largest insect threats for plants such as strawberries, pears, peaches, raspberries, grapes, tomatoes, peppers and of course our grass. Adult Japanese beetles feed on leaves, flowers, or fruits of more than 300 plant species. 


Larvae of Japanese beetles have short spines and white, long brown hairs. They live in lawns and grasslands and eat the roots of the grasses and plants they infest, which damages the ability of the plants to absorb nutrients and water. During larvae stage, Japanese beetles are susceptible to a fatal disease called milky spore disease, caused by the bacteria milky spore. 


Asparagus, citrus fruits, plums, raspberries, and corn are some of the common host plants for adult Japanese beetles. Other plants include turf grass, walnut trees, maple trees and sassafras. They are also fond of particular weeds and non-cultivated plants such as elder, bracken, Indian mallow, poison ivy, wild grape, and smartweed. 


Adult Japanese beetles feed on the upper surface of the plants by chewing the leaves between the veins, which gives the leaves a skeletonized appearance. Trees that have been ruthlessly damaged by Japanese beetles looks like they have been burned by fire. Adult beetles are highly active and travels fast; thus, they can easily infest new areas from a distance of several miles. However, they only make short flights when they feed or lay eggs. 



Picture by James Jordan

Controlling Japanese Beetles 

In Japan, this insect is not a serious plant pest as its natural enemies control its population. On the other hand, Japanese beetles came to the United States without their natural predators. Therefore, there is no check and balance and eventually, they became a serious plant pest. Japanese beetles also found an abundant food supply and favorable climate in the United States. 


Japanese beetle grubs are commonly controlled using preventive soil insecticides, but there are limited options to control adults and larvae. 


Natural Repellents – Using natural repellents, such as catnip, chives, garlic, and dead beetles’ remains have limited effectiveness. Other organisms like nematodes and predatory bacteria are also used to control Japanese beetles. Nematodes attack adult Japanese beetles and kill them from within. 


When existing in small numbers, Japanese beetles can be controlled spraying simple soap-water solution. Spray the solution to the plant, shake the plant in the morning, and dispose the fallen beetles or simply pick them off attractions. Do not leave any traces of Japanese beetle on the plant as it will only attract more insects. 


Pesticides – There are pesticides available that are highly toxic for Japanese beetles but they produce different results. Additionally, Japanese beetles are resistant to both poison and physical damage; hence, a lot of previously successful pesticides are no longer used lately. Similarly, spraying mixture of pesticide and water with garlic cloves and hot pepper can be sprayed all around the garden to kill Japanese beetles. 


Net – Putting a net over strawberry and blueberry bushes can likewise control Japanese beetle attack. Beetles are not smart enough to go into the net as long as it is wide enough to go up and over and back down the other side of the plant. 


Traps – For a swarm of Japanese beetles limited to a small area, the beetles can be physically removed from the plant by placing traps that lure and kill beetles. However, traps can be more destructive when not properly used. Moreover, these traps lure Japanese beetles so they can also result to more and bigger infestation. 


Summer is the time of the year when Japanese beetles damage trees and shrubs. They feed destructively on plants like roses, crape myrtles, hops, canna, grapes, and hydrangeas. Applying a systemic insecticide is prevented in the late winter or early spring to protect plants against Japanese beetles, but at the first signs of damage, spray insecticides are utilized. 



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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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