Night crawlers, or earthworms (Lumbricus terrestris), gain your dirt by enriching it with their droppings, which are called castings. They also aerate the soil so oxygen and moisture can better reach lawn roots. Sometimes the night crawler population becomes too high and the worms start tunneling near the soil surface, which ends in a lumpy lawn with heaps of castings deposited on top the grass. Grub control pesticides get rid of night crawlers without damaging the grass. However, the University of California Integrated Pest Management program doesn’t recommend pesticides for management of night crawlers. Chemicals should only be used when other methods fail, for serious damage and when the number of worms far exceeds what’s necessary for a healthy lawn.

Fix the tines on a dethatching rake so that the rake scrapes down to within 1/2-inch of the crown of the grass, which is heavy enough to scrape excess castings without damaging the grass. Rake the whole yard, removing the surplus castings along with thatch layer, after the lawn has turned entirely green for the season.

Water after dethatching so the top 3 inches of soil is completely moist and saturated.

Fix a hose-end spray applicator so that it’s set to produce 1 1/2 ounces of a grub control pesticide containing fluid carbaryl per 1 gallon of water, or adjust it to the number indicated on the product label. Fill the applicator into the fill line using pesticide.

Spray the whole lawn using the pesticide, coating the grass evenly so both upper and lower leaf surfaces are drenched. Begin spraying in the furthest corner of the lawn, working backward. Stay off the lawn until the compound has dried completely.

Make another application two weeks later if night crawler damage reappears.

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