Hi acharles,

If the conditions are right, disease will occur whether it is rainfall or watering.

The difference is that you can control your watering so as to minimize the amount of available moisture during the overnight period.

The ideal time to water is early morning because the lawn then has all day to dry out before nightfall.

If your lawn is at a point where it needs water, and you can't water in the morning, then just water it whenever you can and deal with any disease problems when and if they occur.

You can of course water during the early afternoon if that is an option for you. The only thing that may occur is that more of the water will evaporate before it gets a chance to soak down into the root zone far enough, and you may have to water longer to get the same results as you would have in the morning.

Hope that helps,
Byron

I thought long and hard about this as well. This is strictly my opinion. Disease in the lawn has a higher probability of developing if it is hot and humid at night. A lot of the time in the summer when it rains it is due to a cold front coming in contact with the hot humid weather. Once the front pushes through there is usually a drop in temperature and humidity so the conditions aren't as great for development as if you simply turned on the sprinklers.

I tend to be less concerned about watering at night when the weather is cool and the humidity is down.

-Mike

And, also, its a bit of "local" issue. Out here on the high, dry high plains, we water in the early morning, like 2AM on, to avoid wet leaves all night, but also avoid the high evaporation rates and wind we contend with in the day.

But, fwiw, I got in a bad habit a few years ago of watering laet in the afternoon to "cool" the yard. I had problems with disease until I quit that practice. The difference between 6 to 8 PM and starting at 2AM was like, night and day. (ha).

I time my watering more to temperature and wind velocity than to the clock.

Watered today, late afternoon and evening, because it was 80F and less than 10mph wind, after it had been 100F+ and 20-30mph wind days, and 80F nights for a week to 10 days.