Grub Control

Grubs can often be present with or without any signs of damage to your lawn. The first key step to gaining control if you notice damage or find grubs is to start with a curative application, following up with preventative applications to help reduce the chances of the grub damage reoccurring. Pheromone traps (Japanese beetle traps or bug bags) are not recommended as they often attract more beetles than they trap, and often cause a more severe problem. The strong scent of the pheromones can attract beetles from several thousand feet away.

Monitoring for Grubs

Monitoring for grubs is important to determine if damage to grass may occur at a later time or if grubs contributed to any current damage. Grubs are often a problem on south facing slopes and grassy areas that get full sun exposure. 

Look for adult grubs, which are in the form of a beetle, in June through early August. Japanese beetles are often found eating on the leaves of many trees and shrubs, while oriental beetles can be found resting on the plants. Where adults are found, females are often laying their eggs nearby in a lawn area.

White grubs can be found April through May and mid-August through mid-October. To inspect a suspected problem area, use a pointed shovel to cut three sides of a square in the turf, 6 to 12 inches in length on each side and about 3 inches deep. Peel back the strip of turf and loosen the soil from the root system. Five to ten grubs per square foot is a tolerable threshold, higher levels require action. If conditions are drier than normal a lower threshold may be used as damage is more serious during dry periods. Be sure to inspect several locations as they may be present in one location, but not others.

Controlling Grubs

Preventative applications can be made with products such as Scott's GrubEx. Apply it between April and May 15th for up to four months of grub control. These types of products kill grubs throughout the feeding season and can be used whether you have identified a grub problem in your lawn or not. A natural alternative to this type of pesticide is Milky Spores, a biological agent that can be applied to lawns in the summer or early fall, before temperatures drop below 65 degrees. Water it in well to penetrate the soil. While a safe and natural solution to grubs, Milky Spores take between one and three years to be effective, and you cannot use any other grub killers on your lawn during that time or it will be rendered ineffective. 

Curative applications should be made when the grubs are actively feeding, in the early spring and fall. We recommend Bayer Complete Insect Killer for use from May to June, and Bayer GrubEx for use from July to September. Watering with approximately ½ an inch of water before and after application will help improve effectiveness. The pre-application watering will help bring grubs closer to the surface. Post-application watering will help bring the product to the grubs. Curative applications are only necessary when there is a known grub problem, therefore checking for grubs is important. 

If you are concerned about using these products in or around a vegetable or herb garden, we suggest using Bonide Eight Insect Control. The granular version of this product can work its way into the soil just like a grub killer but is completely safe around edibles if used eights days prior to harvest.

Stop by The Garden Barn for more information on grub control and how to grow a great lawn.