Weeds in an old lawn, or in a new lawn, can best be combated with chemical weed-killers such as 2,4-D compounds. Using a granulated chemical with a spreader is sometimes preferable to a liquid spray. Spray must be used on a day when there is little or no wind as drifting spray kills and harms vegetables, flowers and shrubs. Feed your lawn after spraying against weeds, so that the grass can thicken up and fill in the bare spots more quickly.

However, one must keep in mind that the best way to prevent weeds in the first place is to have a healthy lawn, with good soil providing sufficient nutrient for the grass you plant. Weeds come in after, when the lawn is badly thinned for one reason or another. For example, a lawn may be thinned by diseases which are overlooked in our haste to lay the blame on weeds. It is true for diseases that commonly attack turf, too, that preventive steps are the best, and that a healthy turf will be better able to ward off the disorders that occur.

As previously stated, a mixture of seeds is more resistant to disease. Excess moisture in the soil seems to be a cause of many diseases. Another cause is poor circulation of air for the grass roots, due to near-by trees, shrubs, and buildings. You can do a little about this by pruning. Close mowing causes some diseases since it weakens the grass and causes more succulent growth, which, in turn, brings about fungal attacks. If the mowing height is not below 1 1/2 inches, even though the lower leaves may be attacked, the newer leaves may not be.

Watering late in the evening is a poor practice because if the grass remains wet at night, disease is invited. And if you use fertilizer to stimulate turf grasses, do so in the early spring and fall when the grass is healthy, not during the summer when the leaf is succulent and tender and easily attacked by disease.

A healthy turf will not in itself combat insects, but they will not be able to do as much damage if the grass is strong. If you suspect insects, such as grubs, roll back a foot of sod. The presence of some insect infestations in your lawn may be disclosed by flocks of birds, such as sparrows, starlings and grackles; they drill holes in the ground with their bills to feed on the grubs, sod webworms and other pests.