Volume 15, No. 1

Glyphosate-resistant weeds
By Kevin Bradley
The following article was written concerning glyphosate-resistant weed development and was prompted, in part, by the of official announcement from Dr. Reid Smeda about the discovery of a glyphosate-resistant common ragweed biotype in Missouri. So far, this common ragweed population is confined to approximately 20 acres in a field with a history of glyphosate use in long-term soybean production. In initial greenhouse experiments, this biotype appears approximately 10 times more resistant to glyphosate than a susceptible common ragweed biotype. In field trials, the addition of lactofen (Cobra or Phoenix) to a standard in-crop glyphosate treatment significantly enhanced control of this species. It was also discovered that glyphosate-treated ragweed plants were infested with a stem boring insect called the ragweed borer, and it is not known if the insect compromised some of the glyphosate activity in the field allowing plants to survive. However, all greenhouse dose-response experiments were conducted in the absence of the ragweed borer. In addition, resistant common ragweed plants exhibit a shorter growth habit, and Dr. Smeda is currently conducting research to determine if herbicide retention is altered, possibly contributing to resistance.
Full article at http://ipm.missouri.edu/ipcm/archives/v15n1/ipmltr1.htm

Soybean rust and crop insurance
By Ray Massey
The USDA Risk Management Agency (RMA) that oversees crop insurance states that “losses to soybean production due to soybean rust disease is an insurable cause of loss provided the insured can verify that the cause was natural and available control measures were properly applied….The RMA will be…vigilant to monitor when outbreaks are detected in an area to determine if an insured could have applied recommended fungicides in a timely manner and did not.” It will be imperative for “producers to keep informed of soybean rust outbreaks in their area and take recommended measures to control or prevent the disease impact if an outbreak is anticipated or already in the area.”
Full article at http://ipm.missouri.edu/ipcm/archives/v15n1/ipmltr2.htm

Early-maturing soybean varieties often yield less than adapted varieties
By Bill Wiebold
Because Asian soybean rust was found in the southern US in late 2004, Missouri farmers may be thinking about planting soybean varieties that mature earlier than varieties adapted to their region. Soybean is highly sensitive to photoperiod, so soybean varieties are adapted to narrow bands that run nearly east and west across the country. The soybean maturity groups associated with Missouri range from MG III in the north to MG V in the south.
Full article at http://ipm.missouri.edu/ipcm/archives/v15n1/ipmltr3.htm