There are several species of insects that live part of their lives as grubs but the ones that cause devastation to the lawn belong to the European chafer. This pest has moved in from the east over the past several years and is now firmly established.

The European chafer has a one year life cycle. The eggs hatch in the soil in late July to early August and the grubs begin to feed on the roots of grass. They feed through the fall and actually do most of their damage during this time of year. When the weather gets cold, they dig deep into the ground for the winter. In the spring when the soils warm, they dig back toward the surface to feed some more. In late June, they turn into a brown beetle that emerges from the ground at sundown. Masses of the beetles swarm in trees, mate and return to the ground to lay their eggs. If they land in your lawn, you will have grubs again.

It takes a lot of grubs to kill your lawn. Research shows that 5 or more grubs per square foot on the average lawn is enough to cause death to the turf. On irrigated lawns, it may take 20 or more per square foot to do the job. That is why one alternative for managing a grub problem is to keep the lawn well-watered throughout the season. This will help the plants survive with a smaller root system caused by the grubs.

Fall is the best time to treat for grubs. They are still small and all of them are near the soil surface until cold weather. Chemicals used for control can easily penetrate to that depth and kill them.

Spring is a more difficult time to get control. The grubs come to the surface as the soil warms and this may vary considerably throughout a single landscape. Some areas warm faster than others in the spring due to soil type and exposure to the sun.

So, it is important to wait to apply insecticides until the grubs are present. Dig down a few inches in several spots in the lawn and see if you find grubs. Wait until you find several with each shovel of soil.

If patches of grass are already dead or if clumps can be raked up without any resistance, it needs to be replaced. A good approach is to rake up all the dead stuff and then work up the soil. Prepare the seedbed properly and make sure that it is graded to remove any irregularities. It is very difficult to remove those bumps and valleys after the grass is established.

Do a final grading, plant the seed and gently tamp it into the ground. If you have a roller, run it over the ground but do not put water in it. You only need a light compaction to be sure the seed is in contact with the soil.

If during the soil preparation, you have been finding a lot of grubs, finish the job by spreading a soil insecticide labeled for use with grubs. These are available at places that sell garden supplies.

By using it at the end of the process, you avoid having to dig and work soil that has already been treated with the pesticide. Plus, in the process of watering your newly seeded area, you will be helping the insecticide to move down into the soil to where the grubs are located.

Regardless of what you do this spring, you need to check for grubs again next fall. About Labor Day, take a shovel and turn over some sod in a few places in the yard. If you find 5 or more grubs per square foot, you need to treat again. If you do a good job of grub control in the fall, you should not have to think about them again until the following fall.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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