Milky Spore and the beetle battle

 

Along the front range, Japanese Beetles are well established. If you are looking for an organic solution for Japanese beetle, start by controlling the Japanese beetle grubs that are in your lawn and garden.   

Milky Spore is a naturally occurring bacterium (Paenibacillus popilliae) used as a biological control to kill Japanese beetle grubs in lawns and gardens. It is highly specific, meaning it only targets Japanese beetle larvae and does not harm humans, pets, beneficial insects, or other wildlife.   

Milky Spore is designed to target and eliminate Japanese beetle grubs in the soil. This biological control method will not affect other common lawn grub species, such as masked chafers, or May/June beetle larvae. The key to Milky Spore effectiveness is to identify the grub you find in your lawn or garden.   

Japanese beetle grubs feature a brown head, 6 legs and V-shaped rear end spines. Other white grubs have orange or grayish heads, 6 legs, and a round/bloated rear end.  

If you’re unsure, bring us a sample of the grubs present in your lawn and we’ll identify it. 

If the grub damage in your lawn is caused by species other than Japanese beetles, Milky Spore will not provide effective control. This trait ensures safety for other beneficial soil insects but also limits the product’s utility to areas where Japanese beetle larvae are present in sufficient numbers.  

If grub populations are too low, the spread of Milky Spore will be limited, and overall effectiveness may be reduced. Therefore, applying Milky Spore is most effective in areas where Japanese beetle larvae are present in significant numbers, ensuring that the bacteria can propagate and provide long-term control. It will work on small populations but will need to be applied seasonally. 

 

Milky Spore is applied three times a year - spring, summer and fall. Once the soil temperature warms —ideally between 60°F and 70°F— the spores activate. 

Japanese beetle grubs ingest the spores while feeding on grass roots. Once ingested, the bacteria multiply rapidly inside the grub, causing the grub’s hemolymph (insect blood) from clear to milky white that kills within 7 to 21 days.  

As the infected grub decomposes, it releases billions of new spores back into the soil, naturally spreading the treatment. In areas with large Japanese beetle grubs, the spore can become self-sustaining. 

 

Milky Spore treatment focuses primarily on lawns because turfgrass serves as the main breeding ground for Japanese beetles. The dense root systems found in grass provide an ideal food source for grubs, making turf grass the area where the beetle population is typically greatest. As a result, treating your lawn directly addresses most Japanese beetle grubs living locally. 

However, it is important to note that Japanese beetle grubs are not limited to lawns alone. If you discover grubs while digging in your garden beds, applying Milky Spore to these areas can be just as effective as treating your turf. By extending treatment to garden beds as well as the soil around roses, peonies and other ornamentals, you can effectively reduce the overall Japanese beetle population on your property. 

Along with Milky Spore, it is important to strengthen lawn vigor with proper watering, mowing, fertilization and aeration; a healthy turf tolerates moderate grub feeding.