Large grub infestations can devastate a lawn, killing patches of grass. The grubs live just under the soil surface and eat grass roots, causing irreparable damage. Typically, the only way to repair the damage is to reseed or resod the affected areas. Treating the lawn with insecticidal spray or insecticidal granules before the damage becomes severe helps to save the lawn. Both the spray and granules perform the same functions, but they have a few differences.
Grubs aren't the only pest that can wreak havoc with your lawn. Symptoms of a grub problem include wilting, yellowing and thinning grass as well as grass that pulls away from the soil easily. Several reasons for dying grass patches exist, however, and they include animal urine and other types of bugs. In order to ensure the problem is grubs before you treat the lawn with a grub insecticide, use a shovel to lift up sections of grass, digging about 2 inches into the soil where the grubs should be evident. Most kinds of grubs are white and 1 inch long or smaller, especially early in summer while they're still young. After confirming a grub infestation, choose either a spray or granule type of grub insecticide. Both forms of insecticide work well, according to the Colorado State University Extension, but one form may meet your needs better than the other form.
When the grubs are in small areas, treating them with a ready-to-use spray is convenient. Such a spray normally is sold in a spray bottle and requires no mixing or preparation; simply point the bottle and spray the grub-affected grass. Concentrated versions of sprays may need to be mixed with water, although some of them come in a bottle designed to connect to a garden hose, automatically diluting themselves as they are sprayed. That feature makes them better than a ready-to-use, bottled spray for large areas affected by grubs. Insecticide granules require the use of a broadcast spreader to apply them evenly, making the granules ideal for use against full-yard grub problems.
Grubs live under the thatch layer and in about the top 1 inch of soil, making targeting them with an insecticidal treatment difficult. Granules and sprays function more effectively against grubs when the treated area is watered immediately after the insecticide application. The water should soak at least the top 1 inch of soil to ensure the insecticide reaches the grubs. Sprays tend to stick to grass blades if the sprays aren't watered into the soil, and granules sit on top of the thatch layer. Some spray leaches into the soil without immediate water application, but the granules continue to stay on top of the soil. Granules tend to be more effective than sprays if you can't water immediately after their application; they'll stay on the soil for a few days without breaking down, allowing you to apply them before an upcoming rainy day or scheduled irrigation time.
Cost and Safety
Because of the convenience of ready-to-use insecticidal sprays, they tend to cost a bit more than other kinds of insecticide. The sprays, however, can drift onto your skin and into your face, exposing you to their chemicals; when using a spray insecticide, wear protective gear, including a long-sleeved shirt, long pants, safety goggles and a dust mask to reduce your exposure to the spray's chemicals. Liquid concentrates typically are less expensive than the ready-to-use sprays, but they must be mixed with water so pose a high risk of exposure for their users. Wearing protective gear can reduce that risk. Granules also are less expensive than the ready-to-use sprays and have a low risk of exposure for their users; the granules combine with inert ingredients, which means little chance exists that an active ingredient of a granular insecticide will touch your skin.
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