The Crop Watch field that we're keeping an eye on this year has now been planted for about 7 weeks. It was planted April 20. After taking a couple extra days to emerge when temperatures turned cool, it has taken of like a rocket. So far the field is uniform with a stand count around 31,000 plants per acre. It received around a half inch of rain in two showers during the last few days of May.
The field was sprayed in mid-May. A few weeds were starting to show up, but most were small, too small to affect yield decisions that the plant was making. The crop was sprayed well before the V5 reproductive stage, where five leaf collars are visible, when agronomists believe some of the early decisions about ear size may be made.
Some plants were larger, but they are very scattered. The one pictured is trumpet creeper, about three weeks after spraying. The crop was sprayed with atrazine plus Impact.
Trumpet creeper is a tough perennial plant. The top growth was burnt back, but obviously the plant survived. Since there are only a few of them scattered through the field, and not a concentration in any one sport, it seems unlikely that they will do any yield damage this season. Shading from the canopy as it closes should help keep weeds in check.
What this survivor does say, however, is that it's difficult to get tough perennial plants with one shot of herbicide. Often they may require special attention. If there was a large patch of them in the field, it might be worth addressing them. As it is, the field would be worth watching in the future to make sure that individual plants don't someday turn into a patch. Since a few of these scattered survivors were noted in scouting, it might be worth noting, either in written records on the field or in computer records. Then you could research ways to control this weed better the next time around. Sometimes it requires a trip through the field with a backpack sprayer, or at least adding a different herbicide to the mix.