Growing Degree Days Through July 2

Jarrod O. Miller, Extension Agronomist,

Corn planted on April 24th in Georgetown tasseled late last week and has been pollinating this week, while corn planted in early May started tasseling on Tuesday. With a cooler spell coming this weekend, corn planted in early May could have better weather during pollination than corn planted mid-April. In the northern end of Delaware, corn planted in mid-April should be tasseling this week, while corn planted early May should start next week.

Daytime temperatures have remained high, but we have been lucky with some cooler nights. When nighttime temperatures drop below 72°F, the corn plant can slow down metabolism. Higher temperatures can cause grain fill and maturity to occur faster, and reduce yield. As you can see in Figure 1, we keep bumping up against that ceiling. Now that we are about to hit the reproductive stage across the state, this 72°F ceiling becomes more important to watch. Rainfall has dropped off significantly across the state, except for Newark. New Castle county has received a significantly greater amount of rainfall than the rest of Delaware since mid-June (Figure 2).

Figure 1: Statewide temperatures since April 1st.

Figure 2: Statewide rainfall accumulation since April 14th.