Organic Lawn Pest Control: Milky Spores and Nematodes

Milky Spores and beneficial nematodes are the two most widely recommended pest control solutions for organic lawn care maintenance. Insect and grub infestations are perhaps one of the biggest challenges for maintainers of organic lawns.

The temptation to simply revert to the use of commercial chemicals and pesticides is great, but with simple applications of Milky Spores and nematodes, insects and grubs can be thwarted, maintaining the health and beauty of your organic lawn and those living and playing on and around it.

As often happens with lawns and gardens, a heavy infestation of one or more type of damaging insect or grub often indicates an imbalance in your lawn’s ecosystem.

Many times, an imbalance is the direct result of the use of wide spectrum pesticides and chemicals meant to solve the problem at hand. Harsh chemicals and pesticides can kill more than just target insects.

Birds and other beneficial, predatory insects that feed on lawn parasites are often killed as well, and in the absence of natural enemies, grubs and parasites may thrive as insect populations reproduce more quickly. To remedy the situation in your organic lawn, you need to reintroduce predators and restore the natural balance so that the one species does not take over without restraint.


Nematodes, commonly referred to as 'beneficial nematodes' or 'predatory nematodes,' are microscopic worms. Beneficial nematodes control insect and grub populations by infecting the host, usually a grub or insect larvae. Nematodes carry bacteria that break down the internal structure of the host (grub or larvae) through enzymes.

Death of the host occurs within 24 to 48 hours. Beneficial nematodes enter through the skin or an orifice on the larvae, mature, and lay their eggs. Once nematode eggs hatch, the young nematode larvae feed on the broken down interior of the insect larvae. Beneficial nematodes go through four stages of growth and exit the host body during their third stage of maturation to begin the cycle again.

Predatory nematodes infect a very wide variety of lawn parasites (over 200 larval insect species) and will kill most of the larval insects invading an organic lawn. As beneficial insect larvae are usually faster moving and more active, they are seldom the victims of nematodes.

Earthworms are not parasitized by nematodes. Predatory nematodes occur naturally and are not considered a threat to humans and pets as there is no evidence that they can survive and develop inside such a host.


Predatory, or beneficial nematodes are most successful when applied to a moist, recently irrigated organic lawn with soil temperatures between 55 and 99 degrees Fahrenheit. Apply nematodes when grubs or larvae are present. It is also a good idea to pay attention to what pests are plaguing the rest of your organic yard and gardens. Remember that most insect invaders start with grub and larval forms in the ground.

If pests have plagued your plants and trees as well, look to the ground. Destructive insects and beetles, such as the highly destructive Japanese beetle, begin as lawn grubs. An application of nematodes can assist in all around organic pest control. Among the many species beneficial nematodes feed on are fleas, gnats, weevils, cutworms, and several species of wood borers.

Beneficial, predatory nematodes are a good ‘quick fix’ for the organic lawn as they begin to kill grubs and larvae within 24 hours of being ingested. Nematodes are a good line of defense also because of the large number of hosts they infect and kill. However, as nematodes are somewhat sensitive to temperature and periods of drought, a second line of defense may be called for to provide long term, lasting grub control. Treatment with a Milky Spore application can be used alone as a defense against White Grubs (Japanese Beetle Larvae), or in partnership with a solution of beneficial nematodes.

Milky Spores

Milky Spore applications work in much the same manner as an infection by nematodes. Milky Spore is a natural bacteria that infects the grubs of Japanese Beetles with Milky Spore Disease. The disease paralyzes and kills the host grub. When the dead grub breaks down, it releases billions of new spores into the soil, which in turn infect and kill other grubs. An infected grub will die within one to three weeks of being infected by Milky Spores.


For the best results, Milky Spores should be applied when white grubs are feeding. Grubs feed during the Spring and Fall. Grubs feed more heavily in the Fall as they are building fat stores and preparing for Winter dormancy. Milky Spore applications begin working immediately if applied while grubs are feeding. Grubs take in the spores when they feed on grass roots. Optimal levels of control occur after one to three years of spore application (the lower timeframe applicable to warmer climates).

Weather is of little concern to Milky Spores, another advantage it has over nematode applications. Milky Spore is not affected by Winter or freezing, and once established, Milky Spore treatments have been proven effective for 15 years or more. Rain is of no consequence to applications of Milky Spore, so long as a heavy rain immediately after application does not wash the applied spore dust away. A light to moderate watering is helpful to help Milky Spores penetrate the soil to where grubs will ingest them. Avoid raking or mowing your yard until the spore has had a chance to soak into your organic lawn.

Like beneficial nematodes, Milky Spores occur naturally and so are not toxic to humans and animals.

Pesticides and chemicals do not effect Milky Spores, so they can be applied even if you have previously treated your lawn with chemical pesticides and fertilizers.Milky Spore is harmless to vegetables, flower gardens, and water supplies. Birds and other wildlife are immune to the effects of Milky Spore as well. Your organic lawn and gardens will benefit from having more healthy birds around to feed on parasitic insects once you have restored the balance to your lawn’s ecosystem by doing no harm to species eating pesticide poisoned grubs and insects.

As an added benefit, you may notice a decline in the activity of small animals that feed on grubs, like moles and skunks. Minus the food source in your lawn, these menacing animals will search for food elsewhere. (Perhaps you will want to share your treatment solutions with your neighbors.)

Both beneficial nematodes and Milky Spores are good courses of treatment for infestations of grubs and pests in your organic lawn. Harmless to nearly everything but the parasites you wish to target, nematodes and Milky Spores are the most widely recommended defenses against organic lawn invaders, eliminating the harm wide spectrum pesticides inflict and restoring balance to the world of your organic lawn and garden.