Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu
Weather has cooled off significantly since mid-June, with most temperatures across the state in the low to 80s over the last week. Many nights have been below 72°F, even falling to the lower 60s, which should help keep plant stress done, especially those fields undergoing pollination (1135-1400 GDD). Most of our fields planted late May and early June should be pollinating right now. In a few weeks, you should scout any early and late-planted fields to compare kernel formation. Many fields planted in April were pollinating during high temperatures and dry weather, and may explain low yields during harvest.
VT: 1135 GDD – Pollination can begin
R1: 1400 GDD – Silking, pollination
R6: 2700 – Blacklayer
Table 1: Accumulated growing degree days based on planting dates through July 24th.
| Sussex | Kent | New Castle | |
| 22-Apr | 1973 | 1925 | 1863 |
| 29-Apr | 1921 | 1879 | 1830 |
| 6-May | 1813 | 1769 | 1731 |
| 13-May | 1709 | 1663 | 1634 |
| 20-May | 1597 | 1556 | 1540 |
| 27-May | 1440 | 1398 | 1392 |
| 3-Jun | 1287 | 1246 | 1242 |
| 10-Jun | 1164 | 1129 | 1128 |
| 17-Jun | 1028 | 1002 | 999 |
Looking at rainfall over the past week, you may see a similar pattern forming. After a very dry June, our rainfall is starting to look like May, with large amounts coming in a short amount of time. It is keeping temperatures cooler, but also limiting the amount of sunlight your plants have for photosynthesis. It appears that the northern end of Delaware is receiving a bit more than sites south of Dover, but Georgetown still leads the pack with at least 22 inches of rainfall since April 22.
