If a lawn was checked at that time of year and more than five to eight grubs found per square foot, chemical control to prevent damage is warranted. An insecticide is probably also needed if the lawn or neighboring lawns had white grub problems last year. Adult beetles which develop from those grubs deposit eggs below the soil surface in mid-July. Upon hatching, these young grubs immediately begin devouring turfgrass roots. The damage occurs when the grubs are half grown and feeding voraciously.
Insecticides are effective against grubs only during the active feeding stage.
The chemical must get into the soil below the thatch, where the young grubs are feeding. If the lawn was not aerated in the spring and there is more than one-half inch of thatch, aeration may be needed before the insecticide is applied. Do this only when weather conditions are cool and moist. Granular formulation of insecticides are best, but solubles and emulsions may be used. Calibrate and apply as stated on the label.