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Posts Tagged ‘grubs in the lawn’

Japanese beetle on a morning glory leaf

Ewwwww! What was that that hit me in the head? Unfortunately, I knew what it was before I reached up to get it out of my hair – a Japanese beetle!

We have been lucky for the past two or three years – the Japanese beetles haven’t been bad at all. This year, they may be back in greater quantities.

They must be starting to emerge now because, just yesterday, I had three separate encounters with these nasty beetles.

A Japanese beetle chews holes in our morning glory leaves.

A Japanese beetle chews holes
in our morning glory leaves.

  1. In the morning I was enjoying coffee on our deck when I noticed a Japanese beetle on a leaf of our heavenly blue morning glories. Upon further inspection, I saw that there were holes in many of the leaves and a few big ones right next to this guy. Ugh! They’ve been feasting on the flowers!
  2. When I got to work, I had an e-mail waiting for me from someone whose 5-year old blueberry bushes were being attacked by Japanese beetles. They were wondering how to get rid of them because they were “beginning to do quite a bit of damage” to the plants.
  3. Then early in the afternoon, I was talking with a customer in the garden center and a Japanese beetle flew into my head and got stuck in my hair! Yuck!

They’re here!

Adult Japanese beetle

Adult Japanese beetle

Japanese beetles are native to Japan – as their name implies. They were brought over to the U.S. accidentally (as is the case for many of our alien pests) in the early 1900’s and are now a major pest throughout most of the eastern United States and beyond. They are about a half inch long with iridescent copper wing covers and a shiny green thorax and head. Their legs have rough spines that get caught in everything – including your hair! Nasty!

Japanese beetles feed on leaf tissue eventually leaving just the veins.

Japanese beetles feed on leaf tissue eventually leaving just the veins.

 

In our area of the Shenandoah Valley, adult Japanese beetles typically begin to emerge from the ground in early July. Almost immediately, they are up and flying around in search of food and mates. We are just starting to see them buzzing around the gardens.

Once they mate, the females will begin to lay eggs in the grass. These eggs hatch about two weeks later and the young larvae (white grubs) burrow down and begin to feed on the roots of the grass.

Beetle grubs devour the tender grass roots killing the grass.

Beetle grubs devour the tender
grass roots killing the grass.

From late August through October, the grubs grow, molt, and continue to feed heavily on the grass roots. This is the time when you will begin to see damage to the turfgrass if you have a heavy infestation. Patches of grass start to turn brown and die. Because the roots are gone, these brown patches can be peeled back easily to reveal the grubs underneath.

Once the weather turns colder in the fall and the soil begins to cool down, the grubs stop feeding and burrow down deeper into the ground where they spend the winter. In the spring when the soil warms a bit, the grubs begin to move up toward the surface and feed on the roots for a short time before they pupate near the surface. The adults emerge in early to mid summer and the cycle begins again.

Japanese beetles have ruined this beautiful Echinacea flower.

Japanese beetles have ruined this beautiful Echinacea flower.

As you can see, these annoying beetles are destructive in two stages of their life cycle; the adults can ruin flowers, foliage, fruits, and vegetables with their feeding and the larvae/grubs can kill large patches of turf as they consume the roots of the grass.

Controlling beetles in the garden

Hand picking is the safest method of control for beetles, however this is often difficult if not impossible to keep up with. If you carry around a small pail with soapy water, you can knock them off into the pail without ever touching them.

Pheromone traps can be used but be sure to place these at the edge of your property and not in or close to your gardens as the attractant will bring the beetles in from all around the neighborhood!

Japanese beetles consume Buddleia flowers

Japanese beetles consume
Buddleia flowers

Control with an insecticide is tricky since Japanese beetles often attack plants that are blooming; eating the foliage or worse, the flowers that the bees and other pollinators frequent.

Bonide Captain Jack’s Deadbug Brew is listed for controlling Japanese beetles and many other pests in the vegetable garden as well as on ornamentals. This product contains spinosad, an insecticide derived from a naturally occurring bacterium. The nice thing about spinosad is that it targets many different plant pests but spares most beneficial insects when used according to the label directions. It is similar in this way to Bt but it lasts longer in the garden and targets a broader range of insect pests.

Bonide Eight is also listed for control of Japanese beetles as well as many other destructive beetles and garden pests. Like Captain Jack’s, it can be used in the vegetable garden as well as on fruit trees and ornamentals. Always use according to the label directions.

A word of caution: Even natural or organic products can be deadly to pollinators like bees. If possible DO NOT spray when plants are in bloom. If this is not possible, spray early in the morning or later in the evening when bees are less active and ALWAYS read and FOLLOW the label directions! Sometimes, for a plant like Buddleia that blooms all summer, Andre will shear off all the flowers before spraying an insecticide.

Of course, controlling the larval stage will help prevent infestations of adult beetles to some extent. Here are some tips for controlling the beetle grubs in your lawn. For these guys, timing is everything!

Hopefully the beetles won’t be too bad this year. We will definitely know soon!

Until next time – Happy Gardening!

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White grubs under the sod

Dead patches in the lawn are typical signs of grubs

Dead patches in the lawn are typical signs of grubs

Andre has the most beautiful lawn.

It’s lush, it’s thick, it’s a lovely deep green …

So when Mark asked me to take some pictures of grubs in his lawn, I was really surprised.

But sure enough, when I went down, I saw several brown patches in the front lawn; one of the telltale signs of grub activity. Some of these patches were quite small and not very obvious but there were also some larger areas that were completely dead.

Damaged turf peels back easily

Damaged turf peels back easily revealing the grubs.

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As is typical of turfgrass that has been fed on by white grubs, the grass in these damaged areas was very easy to peel up because the grubs had literally consumed most of the roots that held it in place. As the turf was rolled back, the soil underneath was littered with white grubs. I have seen pictures of this in books and online, but I’d never actually seen it in person. It was pretty impressive.

White grubs are the larval stage of scarab beetles, a large family of heavy-bodied beetles which include the Japanese beetle, June bugs, and European chafers. They are typically white or pale gray in color with brownish or orange heads and six legs near the head. When found in the soil, they are usually curled up in a characteristic C-shaped position.

White grubs are usually found curled up in a c-shape.

White grubs are usually found curled up in their characteristic C-shape.

Japanese beetle grubs usually get blamed for a lot of the turf damage in our area but I think these grubs may be the larvae of one of the chafer beetles. There were thousands of these reddish brown beetles swarming around at night in July so I wouldn’t be surprised to find a lot of chafer grubs in the soil this fall.

The problem with grubs is that by the time you see the damage to the lawn, it is almost too late to get good control. Understanding the life cycle of these lawn pests is important in determining the optimal time for controlling them.

A heavy infestation was found beside a willow tree near the pond.

A heavy infestation was found beside a willow tree near the pond.

Fortunately, the timing of the life cycle is similar for most of the grubs that feed on grass roots. The cycle begins when the adult beetles emerge from the ground in late June and July, mate, and begin laying eggs in the grass.
Well, I don’t know – which comes first the beetle or the egg!

Anyway, in about 2 weeks or so, the eggs hatch and young larvae (grubs) begin to feed on the roots of the grass. From late August through October, the grubs grow, molt, and continue to feed heavily on the plant roots. This is when you will begin to see damage to the turfgrass.

A grass plant with roots eaten by grubs (right) compared to undamaged grass plants (left)

The roots of the grass plant on the right were eaten by grubs. Undamaged grass plants have healthy roots (left).

Once the weather turns colder and the soil begins to cool down, the grubs stop feeding and burrow down deeper into the ground. At this point applying grub control products is pretty much a waste of time and money. In the spring when the soil warms a bit, the grubs begin to move up toward the surface again and feed on the roots for a short while before they pupate near the surface. Spring treatments are not as successful as late summer treatments because these larger grubs don’t feed much in the spring and the pupae are fairly resistant to insecticides. The adults emerge in early to mid summer and the cycle begins again.

The best time to go after these grubs is when they are small, close to the surface of the soil, and actively feeding on the grass roots. This usually means that most of August is the prime time to apply a grub killer. In September and early October, the grubs are bigger but are still close to the surface and actively feeding on the grass roots.

  • From August through mid-October, control products containing the active ingredient trichlorfon (Dylox) such as Bayer Advanced 24 Hour Grub Control work well when applied according to the label directions.
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  • From May through mid-August, grub control products such as Bonide Annual Grub Beater, Bayer Advanced Season Long Grub Control, or Scotts GrubEx Season-Long Grub Killer can be applied according to the label directions to control grubs in the lawn. (These pesticides may not be available in all states.)

Before deciding on a control strategy, it’s important to determine if chemical control is even warranted. Generally there is a threshold number of grubs (more than 10 grubs per square foot of lawn) above which it might make sense to consider applying a grub control product. There are specific sampling methods that can be used to estimate the number of grubs per square foot in your lawn. The results of this sampling will help you determine whether treatment is necessary. Healthy vigorous grass can usually withstand small populations without much damage and control measures are usually not needed.

Skunks further damaged the turf when they dug for the grubs by the willow tree.

Skunks further damaged the turf when they dug for the grubs by the willow.

A side effect of a heavily or moderately infested lawn is that critters like skunks, raccoons, and moles really love to eat these fat, juicy grubs and will often tear up the lawn digging for them. We saw evidence of this in one heavily infested area at the farm.

Looking at the numbers of grubs that we found in some sections of Andre’s lawn, I think he needs to get out there this weekend and spot treat with a grub control before it’s too late!

Until next time – Happy Gardening!

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