In order to use DD-60's with any confidence, it is helpful to have some historical data for comparison with the current year, and also to have it in a handy form. Slide 1 shows a useful way to assemble this information. In our area we start our chart with the first day of May, the approximate middle of our planting period. Of course, other dates will be a better choice for locations north or south of ours. Also, our growing season ends with the month of September, for we accumulate almost no appreciable heat units after the first of October. In fact, I make it a rule to be fully defoliated by October 1 in order to be sure the defoliants will have enough heat to be effective.

Those people with a computer and spreadsheet program will find this format quite easy to use, but it can also be duplicated simply with a pad and a pencil. Finding long term averages may prove the most difficult problem: the daily data can be worked up from local newspapers. I find the month-to-date and year-to-date columns of most use.