I've noticed quite a few weedy soybean fields around Pennsylvania, probably because of the wet weather and later-emerging weeds.
As of Oct. 18, we have still not had a hard frost in the central part of the state and many of the soybeans are still in the field. Many of the weeds also still have some green and could pose a problem as combines get started.
The list of options outlined below remains the same as in the past for soybeans:
• Clarity: Apply Clarity (dicamba) to actively growing weeds after soybean pods have reached mature brown color and at least 75% leaf drop has occurred. A waiting interval of 14 days is required before harvest. Do not feed soybean fodder or hay following a preharvest application.
• Glyphosate: Apply glyphosate to soybeans after pods have set and lost all green color (80–90% drop of leaves has occurred). Apply glyphosate in 10–20 gallons of water/A to control weeds that may interfere with harvest or to control perennials such as quackgrass or Canada thistle.
Allow a minimum of 7 days between application and harvest. Do not graze or harvest the treated crop for livestock feed within 25 days of application. Do not use on soybeans grown for seed.
• Gramoxone Inteon: Gramoxone (paraquat) may be used for drying certain weeds and quickening berrydrop of Eastern black nightshade just before soybean harvest. Probably the best choice for burcucumber dry down as well. Soybean plants must be mature (65% or more of the seed pods have reached mature brown color or seed moisture is 30% or less).
Apply Gramoxone at 8–16 fl oz/A and include nonionic surfactant at 1 qt/100 gallons of spray. Do not apply within 15 days of harvest. Do not graze or harvest for the forage or hay.
• Aim: Aim herbicide is also labeled as a harvest aid for soybean as well as a number of other crops (corn, sorghum, barley, oats, and wheat). We haven't tested this use, but according to FMC, Aim is particularly suited for morningglories, pigweeds and velvetleaf dessication. Applications should be made when the crop is mature and the grain is drying down.
The application rate is 1 to 2 fl. oz and thorough coverage is necessary (15 to 20 GPA ground application) for good weed control. Aim can be tank-mixed with glyphosate or Gramoxone to hasten dry down or broaden the spectrum.