White grubs are the larval form of the Japanese beetle. Both the grub and the beetle can cause damage to landscapes and gardens. The grubs eat roots under the sod, causing brown spots and streaks, and eventually kill grass. Beetles can defoliate plants and leave eggs on leaves. While chemical treatments can eliminate the problem, home remedies are as effective and cost less. There are a few methods to treat both the grubs and the beetle before it lays eggs.
Biological remedies include controls that kill grubs naturally. Parasitic worms called nematodes are a biological control for grubs. There are two types of nematode: Heterorhabditis spp. and Steinernema spp. Penn State University recommends Steinernema spp. for better results. Nematodes breed inside the grubs and destroy grubs from the inside out.
Use of mild soaps or detergents can work as grub control. Mix the soap with water and spray the mix on the grubs. The chemicals from the soap adhere to the skin of the grubs, causing grubs to suffocate because they breathe through the skin. Fill a spray bottle with the soap and water mixture to apply the soap directly to the lawn. Spraying either during or immediately after rain speeds up the absorption of the soap into the ground and to the grubs.
Handpicking grubs and Japanese beetles is a way to control minor infestations. The Ohio State University Extension Service states that placing grubs or beetles into a jar filled with soapy water will drown the insects. Seal the jar to ensure the insects remain inside. Dump out the water with the dead insects into the compost pile. Set up a passive trap mixture of sugar, vinegar and soap in water that will attract Japanese beetles to the container; when the beetles are in the container they drown from the soap and water. Allow the container to fill with dead insects, then dump and rinse to repeat the process.
Use plants as both landscape and deterrent for adult beetles. Plant garlic or clove as borders or accents in the landscape. The odor of either repels beetles. Break up the garlic into individual parts and plant each to grow into a separate plant. Chives are useful in patches and along the exterior of lawns and landscapes.
Before using any home remedy, identify the severity of the infestation. Collect grub samples in mid-August while the grubs are growing. Cornell University recommends random samples taken in locations 10 feet apart; add areas where grubs were spotted previously with the sample. Cut squares into the sod at the chosen locations and peel back the sod. Grubs will be underneath the sod. Determine the severity of the problem by the number of grubs found per square foot of sod. According to Cornell, finding greater than 10 grubs per square foot indicates an immediate need for treatment while fewer than 10 indicates treatment should be considered but is not an immediate concern.