Growing Degree Days Through July 10

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu

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 10^th

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

Figure 1: Statewide temperatures since April 1^st.

 Figure 2: Statewide rainfall accumulation since April 14^th.