Milky spores and nematodes offer chemical-free, biological control of white grubs. White grubs are the larval stage of invasive beetles that feed on grasses and ornamental plants. Consider using milky spores and nematodes to rid your landscape of white grubs. They are natural enemies and prevent the further damage to your plants often caused by insecticides.
When the larval stage of Japanese beetles (Scarabaeidae) infests your lawn by inhabiting your soil, a white grub problem is apparent. White grubs can severely damage your turf grass and ornamental plants by feeding on roots, causing thinning, wilting or death of grass and plants. Additionally, animals that feed on white grubs like birds and mammals may cause secondary damage when they remove grubs from your soil, according to the University of Missouri Extension. With a white appearance in the larval stage, many adult white grub beetles measure less than one inch in length and display a light brown to dark brown color. Feeding occurs during the spring season.
Milky Spore Description
Milky spore (Paenibacillus popillae) is a bacterial disease used in the fight against white grub infestations. Though the insecticides trichlorfton and imidacloprid are effective against white grubs, their minimal damage is unnecessary in comparison to the lack of damage caused by milky spores. Milky spores are microbial-based and applied to grasses in the form of dust. Since this bacterium does not multiply on artificial substances, it is easily controlled and site specific, according to the University of Illinois Extension. Optimal soil temperatures for milky spore use are 60 to 70 degrees Fahrenheit.
Milky Spore Grub Control
Milky spore disease controls grubs only when they ingest the bacteria. Once ingested, the bacteria multiplies within the grub's body. White grubs' bodies are filled with a fluid called "hemolymph." The milky spore disease causes this clear liquid to turn white, leading to the death of the insect and the release of bacterial spores into surrounding soil. Though an insect may eat the bacteria and suffer no ill effects due to rapid digestion that does not allow absorption of the disease, milky spores are highly effective and usually reproduce once ingested, according to the University of Illinois Extension. Milky spore disease offers continual control, as it may survive in soil for up to 20 years.
Nematodes are another option of biological control in managing and killing white grubs in your lawn. Often referred to as beneficial nematodes for their ability to control pest problems, nematodes are parasitic round worms that reproduce in abundance within soil, according to the Colorado State University Extension. In controlling grubs, the species most often employed are Heterorhabditis bacteriophora and Steinernema glaseri. Because they are easily damaged by extreme temperatures, keep beneficial nematodes in soil above 55 degrees Fahrenheit and below 90 degrees Fahrenheit.
Nematode Grub Control
To control white grubs with beneficial nematode use, release nematodes into grass where they search for insects. Nematodes enter grubs through body cavities like the mouth or anus. Once within the insect, the beetle dies within three days. Nematodes excrete a bacteria in the insect host's body that multiplies and becomes toxic; blood poisoning occurs at a lethal level to the white grubs, according to the Colorado State University Extension.