I received a question about early harvest aid applications in soybeans from an area grower last week. Eric Prostko, UGA Weed Scientist, recently sent out some information on this subject.
Soybean growers who want to use paraquat as a harvest aid, should be warned not to apply too early. Early applications (>40% seed moisture) will likely result in significant soybean yield loss as a result of reduced seed weights. The 40% seed moisture contest roughly coincides with the R6.5 to R7 stages of growth. R6.5 = Full Seed = all normal pods on 4 uppermost nodes have pod cavities filled. R7 = Beginning Maturity = one normal pod on main stem of all plants has reached mature color. Official UGA soybean harvest aid recommendations can be found on page 517 of the 2014 UGA Pest Management Handbook.