When to Apply Grub Killer in Ontario

In the lush provinces of Ontario, where the season's transitions bring about a vibrant display of nature's wonders, the timely application of grub killer becomes a pivotal task for gardeners and homeowners alike. With the emergence of summer, nestled between the months of late June and early August, the hatching of grub larvae beckons the need for immediate action. Within the narrow window of approximately two to three weeks following the peak timing for adult beetles, the application of grub killer becomes imperative to control the burgeoning population. Amidst this changing landscape, the judicious application of grub killer assumes it’s rightful place as a guardian of lawns and gardens, diligently combating the ever-encroaching threat.

Can I Apply Grub Killer in the Fall?

Grubs can be a nuisance for homeowners in Ontario, causing damage to lawns and gardens. To effectively combat this problem, it’s important to know when to apply grub killer. Fortunately, there are two chemicals, carbaryl and trichlorfon, that can be used in both spring and early fall to control grubs.

In terms of effectiveness, these chemicals can be up to 80% effective in September and 55% effective in October. Applying it during this period ensures that the chemicals have enough time to penetrate the soil and kill the grubs before they cause further damage.

However, it’s important to note that applying grub killer in the fall shouldn’t be delayed beyond October. This is because the effectiveness of the chemicals diminishes greatly as the temperatures drop and the grubs become less active.

When applying grub killer, it’s essential to carefully read and follow the instructions provided by the manufacturer. Different products may have different application rates and methods, so it’s crucial to use the product as directed for optimal results.

In addition to using grub killer, it’s also important to implement other preventive measures to minimize grub infestations. This includes regular maintenance of the lawn, such as proper mowing, watering, and fertilizing. A healthy and well-maintained lawn is less susceptible to grub damage.

Using the chemicals carbaryl and trichlorfon in early fall, such as September and October, can yield good results.

Now that we know when grubs are most active and voracious in their feeding habits, it’s crucial to understand the appropriate timing for applying grub treatments aimed at eliminating their existing population. The ideal timeframe for such treatments spans from the middle of summer to September, coinciding with the period when grubs feed the most. Additionally, targeting grubs before they undergo metamorphosis into adult beetles is highly recommended. By seizing this prime opportunity, effective control measures can be implemented to combat these destructive pests.

When Should You Kill Grubs?

When should you kill grubs? Grub treatments that aim to kill the existing population should be applied any time through the middle of summer until September, which is when they feed the most. It’s also prime time to target grubs before they turn into adult beetles.

Grubs are the larvae of beetles, such as the Japanese Beetle and the European Chafer Beetle. These pests can wreak havoc on lawns and gardens, causing significant damage to the root systems of grass and plants. In order to effectively control the grub population and prevent further damage, it’s important to apply grub killer at the right time.

Applying grub killer during the summer months is crucial because this is when grubs are actively feeding on the roots of grass and plants. By targeting them during this period, you can ensure that the treatment is most effective in eliminating the population and preventing further destruction to your lawn.

In Ontario, the weather conditions and the beetle population can vary from year to year. It’s important to monitor your lawn and look for signs of grub infestation, such as wilting grass, brown patches, and loose sod. If you notice these symptoms, it’s recommended to apply a grub killer treatment as soon as possible.

Different Types of Grubs and Their Impact: This Topic Could Provide Information on the Different Types of Grubs, Such as the Japanese Beetle and the European Chafer Beetle, and the Specific Damage They Can Cause to Lawns and Gardens. It Could Also Include Information on Other Pests That May Be Mistaken for Grubs.

  • Different types of grubs and their impact:
  • Japanese Beetle – These grubs can cause significant damage to lawns and gardens by feeding on the roots of plants, resulting in patches of dead or dying grass and weakened vegetation.
  • European Chafer Beetle – This type of grub also feeds on the roots of plants, leading to similar damage as the Japanese Beetle. They can be particularly destructive in large numbers.
  • Other pests mistaken for grubs – Some insects, such as cutworms and wireworms, are often mistaken for grubs. These pests can also cause harm to plants and should be properly identified for effective control measures.


By targeting the different stages of the grub larvae, homeowners can tackle the problem during two key seasons: summer and fall. In late August to September, another round of application is advised to tackle the new grubs that have hatched from beetle eggs throughout the summer.

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