When To Apply Grubex

Are you at a loss why your lawn has these brown dead patches every summer? You may need to check for grubs, which are among the most common causes of lawn damage.

Beetles burrow into your lawn to lay their eggs. Grubs are often from June bugs, Japanese beetles, Oriental beetles, and European Chafers and reappear season to season until they mature.

Fortunately, as this is a common issue, there is a common remedy. Grubex is available as an insecticide and a preventative insecticide treatment. When used correctly, it can deal with your grub infestation. However, if you want your grub control to work as it is supposed to, you need to apply it at the right time.


When signs of an active infestation first develop, usually later in the grasses’ growing season, grub control chemicals can be used; however, there are specific times to use such treatments for when grubs hatch, which is late spring or early summer. (Read Does Grass Seed Go Bad)

It may take several seasons to extinguish your grub infestation using your chosen grub control method.

In our guide, you can learn the best time to apply Grubex for the best effect. By the end, you’ll know more about when to put down Grubex and about applying grub control to deal with controlling grubs and emerging larvae issues to get back your healthy lawn.

When Should I Apply Scotts GrubEx?

With Scotts GrubEx Season Long Grub Killer, you can keep grubs from ruining your lawn. All season long, a single spray can stop and prevent grubs. To kill grubs as they develop, apply in the spring, or early summer kills them as the eggs hatch.

However, Scotts GrubEx Season Long grub killer can help manage Japanese beetle and Armyworm infestations by using it once a year. To stop grub worms before they damage your lawn, apply your premium grub control with a broadcast, drop, handheld, or Wizz spreader. (Read About Scotts Weed And Feed Spray)

Only after determining the type of pesticide to be used can the question of when to apply grub control be answered. A grub preventer might be the way to go if you know your lawn already has a pest problem and want to get ahead of it this year.

Any grub preventer should be applied immediately before the grubs hatch when you have observed rapid brown spots and lawn damage in previous summers.

However, if you are well into the growing season and have noticed grub damage to your lawn, it is too late to take preventative measures. You’ll need to use a standard grub killer at this stage.

Grub control, when used correctly, can kill any pests it comes into touch with; therefore, it may be used whenever you notice grubs are active. This normally corresponds to the growing season of your lawn.

dewdrop from rain

Should I Apply GrubEx Before Rain?

Grubs are most harmful when sitting just beneath the soil’s surface, contentedly feasting on grassroots. Therefore, whether you apply grub control as a preventative measure or not, the most important thing to remember is to water the solution.

This ensures that the insecticide soaks into the soil rather than sitting on the top. When you apply grub control, keep the following in mind to ensure confirmed grub damage.

  • Dethatch or rake away dead grass from any affected areas
  • Apply your premium insect control on relatively dry soil
  • Remember, you are using a hazardous chemical solution, so always wear rubber gloves and follow the label instructions
  • You can apply grub control when some rain is forecast, yet heavy rainfall could wash your grub control pesticides away
  • Water half an inch to an inch deep after applying

Proper lawn care is applied afterward to ensure the grub control solution goes where it needs to go.

Because grubs live in the soil, the grub killer must be watered in. Instead of just sitting on top of the grass, the grub killer granules will reach the roots. Make sure you water the treated area with a half-inch of water.

In the coming week, keep an eye out for grubs or other activities on your lawn. If the grubs haven’t died off, you may need to reapply. Always read and follow the instructions label, but you may need a larger dosage.

White grub damage to lawns can occur after mid-August. Our previous experience has been that grub damage is not apparent until September or possibly October. White grubs mainly cause localized damage. Severe damage is common in irregular and isolated areas where soil-dwelling larvae eat the grass plant roots.

Drought stress can often mask damage caused by white grub damage. Severe damage generates large irregular patches of dying turf; you can roll back like a carpet. You’ll discover raccoons or skunks will hunt for large concentrations of grubs, and while it helps control grubs, they make a mess of your lawn area.

Rainfall and soil moisture affect killing grubs, as mid-summer moisture favors beetle activity and grub development.

In August and September, when Japanese beetles grubs are active, damage may not be visible because of grass growth masking the root injury. Turf can withstand up to 20 grub worms per square foot before it shows any sign of damage.

Late summer treatment to apply grub control is tricky, as using insecticide for Japanese beetles white grubs isn’t sure to work. It’s hard to kill white grubs by September, and even the best chemical compound may not kill enough to prevent future grub problems.

Preventive insecticides treatments after early October are ineffective and not recommended. If you do treat, you may not need to treat the entire lawn. Treat grub “hotspots” discovered by turf damage by observation or testing for grub worms or issues from Asiatic garden beetles or more.


Is It Too Late to Treat for Grubs?

Knowing your lawn’s size is the first step in grub control. You can’t even buy grub control products without knowing the treatment area. You don’t have to be exact. Aim for 1,000 square feet.

Next, put down the relevant product. Grubs live through several stages, and the chemicals can kill grubs at various stages during their lives. Thus, you can easily waste money and not kill grubs in your lawn if you use the wrong product for the present life cycle.

Preventive Treatments

The most effective product will be a preventive insecticide. Such pesticides won’t work in the spring, yet work effectively on newly hatched grubs in July, but not on large mature grubs from September to May.

Depending on the active component, there are varying application times recommended. Any products containing imidacloprid, thiamethoxam, clothianidin, and insecticides called Chlorantraniliprole need applying and watering into your soil in June or July.

The pesticide may have moved through the soil or degraded when the grubs hatch in late July. Preventative products may not work on large grubs if applied too late.

These products will reliably lower 75-100 percent of the grubs when the best time to happy is June or July and watered in using half an inch of water soon after application. If you lack an irrigation system, use lawn sprinklers.

Because it is less water-soluble than the other preventive compounds mentioned above, it can be applied after the grass turns to turn green in the spring.

Creating a more dense turf over a couple of years can help your lawn be grub resistant to protect the root system. In addition, if you found visible damage or grubs found from the previous fall, this shows you need Grubex; when to apply Chlorantraniliprole can have the best time to apply from April until mid-July.

Apply before June; you can prevent grub damage and see a reduced number of grubs by 65-80%. (Read our Lawn Fertilizer Schedule)

Curative Treatments

Carbaryl and trichlorfon are considered curative treatments and are toxic compounds that can kill grubs at all stages. The two insecticides here are your only options to prevent grubs found in large quantities in the fall or early spring.

Research shows it can kill 20-80% of active grubs when applied in September by 20-55 per cent when applied in late October.

For stopping the grubs from reaching the stage of adult beetles that can then lay eggs, these curative treatments are less effective than preventive compounds and often suited to small grubs.

Consider whether it is better to delay a preventive measure than treat your lawn immediately with a less effective product. For best results, maintain the infested lawn moist and nourished, and treat it again with a preventive application the following summer, or the problem will likely reappear in the fall or spring.

Like other treatments, research dictates that to ensure it prevents grubs from developing any further, you need irrigation immediately after application with 0.5 inches of water.

Other research shows carbaryl can be more effective than trichlorfon against European chafers grubs. For Japanese beetle grubs, both compounds work well from the larval stage upward. After the insecticide is applied, the grubs die in 10-14 days.

The name of one trichlorfon product shows it can kill grubs in 24 hours. However, it’s best to wait five days after trichlorfon application and three to four weeks after carbaryl application to show the effectiveness of controlling grubs and if there are newly hatched grubs present.

After May 15, do not apply curative compounds because grubs stop feeding to pupate.

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