CONTROL ANNUAL WEEDS: The Penn State Extension has provided some helpful tips for controlling summer weeds before the seeds set, where possible.

Preventing seed production is important for driving down the weed seed bank and reducing the need for weed control inputs (i.e. herbicides). In particular, it is easy to prevent weed seed production following a cereal grain such as wheat, barley, or oats as well as some vegetable crops such as sweet corn or snap beans. Proper timing of the control practice is essential in preventing seed production.

Below is a summary of estimated seed drop for various weed species:

Giant foxtail: late August and peak seed rain occurred from late September through the month of October

Yellow foxtail: began in early August and continued into late October

Pigweed species: begin to produce mature seed by mid-August

Lambsquarters and ragweed: generally, do not mature until the month of September

Palmer amaranth or waterhemp: make sure to monitor them routinely over the next couple months and control any regrowth or new seedlings before they set seed. Palmer amaranth plants notoriously retain their seeds late into the summer and fall and thus seeds don’t necessarily fall to the ground upon maturity but are usually spread via the combine.

To prevent seed production, fields can be sprayed with an effective herbicide or mowed once or twice. With giant foxtail, even treating the field by mid-September would have greatly reduced seed production in our experiment.

Taking the time to prevent seed production this year can make a big difference next year. About 80% of weeds next season come from weed seed this fall.