Early fall is the best time to apply milky spore. At this time of year, Japanese beetle grubs are feeding aggressively. This increases the chance that they will ingest the bacteria in milky spore, which will then kill the grubs. If you wish, you can apply milky spore effectively any time the soil is not frozen. So, spring and summer applications can be effective if soil temperatures are in the proper range. In fact, treating your lawn with milky spore in spring, summer, and fall can protect against grubs for many years to come.
What is Milky Spore Used For?
Milky spore is used to kill Japanese beetle grubs. Milky spore products contain Paenibacillus popilliae bacteria. This bacteria only attacks the larval stage of Japanese beetles, which are white grubs. These grubs feed on grass roots. So, killing grubs with milky spore can help your lawn recover from dead spots and catastrophic damage caused by grubs.
- Milky spore contains bacteria that kills Japanese beetle grubs.
- Japanese beetle grubs are the only grub that will be killed by milky spore.
- Compare milky spore vs. GrubEx to see which grub killer is best for your yard.
It is essential to keep in mind that milky spore only kills Japanese beetle grubs. If the grubs in your yard are from a different species, milky spore won’t have any effect. So, if you don’t see any benefit from milky spore, you may need to use a broad-spectrum grub-killing pesticide.
What are the Signs It’s Time to Apply Milky Spore?
The first sign that it’s time to apply milky spore is that the soil is unfrozen. The second is that the soil temperature is between 60℉ and 70℉ (16–21℃). You can check the soil temperature in your area with this online tool. Usually, soil temperatures reach this optimal range in spring and fall, which makes these times ideal for milky spore application. Spreading milky spore when the soil is too cold or too hot will render the application useless because the bacteria will not survive to infect grubs.
- It is early fall, from September through October.
- The soil is not frozen.
- Soil temperatures are 60–70℉ (16–21℃).
The months of September and October are the best time to apply milky spore. During fall, grubs are extremely active. They feed aggressively to store energy for the dormant winter months. Time your milky spore application when soil temperatures drop down into the ideal range in early fall. This way, the P. popilliae bacteria is active in the soil when grubs are feeding the most. This ensures the grubs will ingest the bacteria and be killed by it.
When Should You Not Apply Milky Spore?
Never apply milky spore when the ground is frozen. The months of November through February are not a good choice for milky spore application. Grubs are inactive during cold weather. Since milky spore only kills grubs when they eat the bacteria, treating a lawn with dormant grubs won’t have any impact.
- Do not apply milky spore to a frozen or frosty yard.
- Grubs are inactive in cold weather, so they won’t consume the milky spore and die.
- If there is a summer heatwave, wait until the weather cools off before using milky spore.
- Intense heat and low soil moisture can make milky spore treatments less effective.
Although you can apply milky spore during hot, dry weather, it may be less effective. For this reason, it’s often a good idea to avoid using milky spore during the height of summer, from July through August. The bacteria in milky spore is less effective when the soil is hot and low in moisture.
Can You Apply Milky Spore in Spring?
Spring applications of milky spore powder can be very effective. As the grubs in your soil exit winter dormancy and begin feeding again, you can kill a sizable portion of the population with milky spore. Wait until after the last average spring frost. Then, make your milky spore application. If you are using milky spore powder, you will need a drop spreader. If you decide to use milky spore granules, you can spread them with the same tool used to spread grass seed or fertilizer.
- Spring is the second best time to apply milky spore, just behind fall.
- It is better to apply milky spore in spring than winter or summer.
- Time your application after the last frost of spring.
- Decide whether you want to use milky spore powder or granules.
If you miss your window to apply milky spore powder in fall, don’t worry. Milky spore lasts a surprisingly long time when you store it. So, you can wait until next spring—when soil temperatures rise into the ideal range—to make your application
How Often Do You Need to Apply Milky Spore?
To build a large population of grub-killing bacteria in the soil, apply milky spore 3 times per year for 2 to 3 years. The first application should be made in spring, the second in early summer, and the third in fall. This will gradually kill off more and more grubs until your lawn is no longer being destroyed by them.
- To get the most out of milky spore, apply it in spring, summer, and fall.
- Repeat this 3-times-per-year application schedule for 2 to 3 years.
- After 2 to 3 years of treatment, milky spore will remain in the soil for up to 20 years without any further applications.
The best part about applying milky spore for 2 to 3 years is that after this period, you do not have to make any more applications for 10 to 20 years. Milky spore can survive in the soil—and continue to kill grubs—for more than a decade. So, treating your yard with milky spore aggressively for a few years can reduce your future lawncare workload. Plus, it will save you money when compared to pesticidal grub killers that must be used every year.
What is the Best Time to Apply Milky Spore?
To properly time your milky spore application, remember these tips:
- Milky spore is most effective when applied in early fall.
- Spring and summer applications of milky spore are also effective.
- Never apply milky spore when the ground is frozen—it will be useless at this time.
- The ideal soil temperature for milky spore application is 60–70℉ (16–21℃).
- To protect your yard, apply milky spore in spring, summer, and fall for 2 to 3 consecutive years.
- After treating your lawn for a few years, milky spore will remain in the soil for 10–20 years, even if you don’t perform any more applications.
Milky spore is a powerful, organic grub killer that targets an invasive species. It is safe for the environment, so it is a great choice if you wish to avoid using pesticides. Just make sure to time your applications right to get the most out of your milky spore.