“When you turn a mechanical harvester around at the end of the row, whole weeds can get pulled into the harvester,” Vann said. “We don't want to get this contamination outside the actual planting.”

The most important step in controlling pigweed in tobacco, said Vann is don't plant in weedy soil in the first place. “Field choice can really help in solving this problem.”

Ironically, tobacco farmers have a few advantages compared to other crops in controlling pigweed:

• Cultivation: “We still cultivate tobacco after transplanting ,” Vann said. “That is unlike most other row crops and gives additional chances to control pigweed.”

• The opportunity to hand pull: “Most tobacco farmers use hand crews to top and sucker, and these workers can pull up larger weeds while they are out there,” he said. “There is a lot to be said about getting the seed out of the ground altogether. That certainly reduces the seed bank for future crops.”

But it takes roughly one person to hand weed one acre. ”As you get over a certain acreage, this becomes hard to do,” Vann said.

• Effective available herbicides: Vann says three herbicides will probably play the most important roles in the current situation — Spartan, Prowl and Aim.

Spartan will probably give better control of pigweed than the other two. It does extremely well on pigweed, and about half the crop now is getting an application of Spartan.

Aim has an unusual fit in tobacco. “You apply it just after first harvest, and it works well,” he said. “But the pigweeds need to be two to three inches tall for good results. If they are bigger, there may be some initial control but there will be a rebound later.”

• Deep tillage with a moldboard plow. This is something of a new concept, but Vann says that in field testing, it has been shown that deep tillage can substantially improve your pigweed control. “It gave a reduction of about 50 percent in pigweed,” said Vann. “If we included application of Spartan, the reduction was 80 percent.”