White grubs are the larvae of beetles. The larvae all have six strong legs near the head, and are white. They vary in other characteristics such as size, head color, and hair patterns on the body. These grubs feed on roots of various plants. Your garden plants, lawn and even potted plants can be attacked by grubs.
In general, white grubs have a one or two year life cycle, depending on the type of grub. The following describes a one year life cycle.
Spring - The grubs are fully grown larvae and are actively feeding.
Summer - The grubs turn into pupae and pupate into beetles. This generally occurs around June in the northern US and Canada.
The beetles only live for about a week, mating and laying eggs. These eggs hatch a few weeks later.
Fall - The new grubs feed until temperatures drop and they burrow deep in the soil to avoid freezing, and emerge the following spring.
Many grubs only cause minor damage and control strategies are not required.
There are a few grubs, like European Chafer, that commonly cause extensive damage to lawns. The grubs eat the roots of the lawn, and the lawn dies. As few as five grubs per square foot can cause extensive damage.
Major damage can also occur when raccoons, skunks, and crows rip the lawn apart while feeding on the grubs.
The most important thing to do to reduce grub damage is to ensure a healthy, robust lawn. This means regular feedings and annual core aeration to encourage a strong, dense root system. If the lawn has a dense root system, it will tolerate minor feeding by the grubs.