Thursday, July 10, 2014

Time to change direction

Below are some pictures of waterhemp, both were very tall (12-15") and both were treated with a quart of Roundup.  They were also found about 3 feet apart in the same field.  The surviving 12-15 inch tall waterhemp looks very healthy and coming back another quart of Roundup will most likely do nothing to impede its existence.  In fact, effective chemical control options are limited for the surviving individual in this year.  In future years it will be necessary to start with a strong preemergence herbicide program and then follow with alternative modes of action for postemergence control.



Given the fact that waterhemp can continue to emerge late into the season, it would be wisest to use postemegence herbicide options with some residual control.  In this particular field more flushes of weeds are coming, including some waterhemp along with some grass. A different mode of action will need to be used, and as for the tall survivor, it is advisable to get out and prevent this individual for flowering (hand pulling). It is the only way to keep this problem from persisting for years to come and to reverse this course.


Time to look for soybean cyst nematode

Visual symptoms of soybean cyst nematode (SCN) are showing in soybeans:



Not all fields will have this degree of chlorosis and stunting (above picture), this is a severely infested farm and a non-resistant soybean.  More often symptoms are much more subtle.  In the picture below the farm is moderately infested with SCN (manageable levels) on the left is non-resistant soybean and on the right is a resistant soybean. Notice the slight differences in growth.

These above ground symptoms are not always the most visible, so it a good time to check roots for the presence of females (picture below).  The nematodes will be much smaller than the root nodules and may require the use of a hand less or reading glasses for some people. The picture below is of a RESISTANT soybean, notice you can still observe females at low levels on this plant.

More on SCN management:http://www.extension.umn.edu/agriculture/soybean/soybean-cyst-nematode/



Soybean Aphids Appearing in latest Planted Soybeans

Its that time of year again to start monitor soybean aphid levels.  On July 9th we found some early colonization in the upper leaves of late May planted soybeans.  Levels were very low and do NOT require an insecticide application.  Unnecessary early applications of insecticide not only cost money, they can lead to many negative side effects including the need for more applications once aphids recolonize treated fields.

For more info on soybean aphid: http://wiki.bugwood.org/NPIPM:Soybean_aphid