Growing Degree Days Through July 10

Jarrod O. Miller, Extension Agronomist,

Corn planted in late May should be in tassel or at least at V15 across Delaware. Most corn planted from mid-April to mid-May is probably on the reproductive stages (Table 1), so be sure to keep the irrigation running to keep plants cooled and less stressed during grain fill.

It has been hard to miss daytime stress on corn, as temperatures have remained high (>87°F) for much of the past month (Fig. 1). Nighttime temperatures have had a little reprieve, but still appear to be on a linear upward trend as we head into mid-July. At this point, the best you can do to keep stress down is making sure that irrigated fields are tended to. Temperatures through next weekend appear to be hot and humid again.

The northern end of Delaware is still getting most of the rainfall, while storms keep skirting just south of the Mason-Dixon line in Delmar (Fig. 2). Over the last month Delmar has received less than an inch of rainfall, while Newark has received three.

Table 1: Accumulated growing degree-days based on planting dates through July 10th

If you planted

Sussex Kent New Castle
14-Apr 1733 1685 1614
21-Apr 1642 1593 1527
28-Apr 1561 1518 1447
5-May 1460 1436 1376
12-May 1360 1339 1285
19-May 1290 1274 1225
26-May 1150 1138 1091

V6 = 475 GDD, V12 = 870 GDD, VT = 1135 GDD, R1 = 1400 GDD

Figure 1: Statewide temperatures since April 1st.


 Figure 2: Statewide rainfall accumulation since April 14th.