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Do Grubs Kill Trees?

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It can be frustrating for a gardener or landscaper to deal with the death of plants, especially trees. It can become aggravating when the death of these plants seems to stem from an unknown cause. Large numbers of grubs can be troublesome, as they can cause serious damage. In a single lawn, there can be up to 24 different species of grubs present, making them a serious pest.

Identification: Grubs

Grubs are small white insects that are the larval stage of various species of beetles. These insects take on a distinctive ‘C’ shape, making them relatively easy to identify. Adult beetles lay their eggs in the soil during the mid summer, generally in areas that receive plenty of water and full sun. The eggs develop into grubs toward the end of the summer and begin feeding, which results in damage to the roots of plants.

Food Sources for Grubs

The most well-known food source of grubs are the roots of the lawn. If the lawn is dead or dying, such as due to extreme drought, the grubs will begin to feed on roots of any nearby plants, in an attempt to survive. This can include the roots of various species of trees.

Removing Existing Grubs From the Yard

The best time to apply grub treatment to a yard is when the eggs are in the hatching phase, generally around June or July. A good rule of thumb is to apply the treatment when a large number of adult beetles suddenly begin to appear and are seen flying or in trees around the yard. Treatments should be applied according to the manufacturer’s recommendations, which is often after the lawn has recently been watered. Treatment in the spring is not recommended, as grubs are already maturing and therefore are not as easily controlled. Furthermore, during the spring, plants are actively growing and generally do not show the same signs of damage.


Many grubs have a one-year life span, while others may have a three-year lifespan; therefore prevention must be ongoing. This is especially true if grubs have been an issue in the past. The appropriate insecticides should be applied seasonally as needed to prevent the occurrence of grubs, often in the mid-summer. Grubs thrive in well-watered lawns, so less frequent waterings can help reduce the survival rates for grubs throughout the season.

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