Roundup Ready Alfalfa Update 

        If you haven’t heard by now, there won’t be any new seedings of Roundup Ready alfalfa put in the ground anytime soon.  After hearing additional testimony and reviewing additional data, the a Circuit Court judge from California ruled that Roundup Ready alfalfa seed will continue to be a regulated commodity and no new Roundup Ready alfalfa stands can be planted.  This ruling will remain in effect until USDA-APHIS conducts an Environmental Impact Statement (EIS) for Roundup Ready alfalfa.  While it is not known how long this process will take, it is expected that writing the EIS will take 1-2 years to complete. 

        What does this mean for Roundup Ready alfalfa that is currently being grown?  The judge did not restrict the growth or sale, but did place specific restrictions on how to manage those fields.  They are:  

Roundup Ready alfalfa planted before March 30, 2007 may be grown, harvested and sold subject to the following conditions.

I.   Pollinators shall not be added to Roundup Ready alfalfa fields grown only for hay production.

II.  Farm equipment used in Roundup Ready alfalfa production shall be properly cleaned after use.

III. Roundup Ready alfalfa shall be handled and clearly identified to minimize commingling after harvest. Immediately after harvest, growers or seed producers shall store Roundup Ready alfalfa in specifically designated and clearly labeled containers (editorial note: this makes it sound like storing alfalfa is the same as storing left over mashed potatoes). 

        USDA-APHIS is responsible for providing instructions on how growers shall clean their equipment and how to properly store Roundup Ready alfalfa.  The important consideration is that no restrictions are in effect until individual growers receive notice from APHIS. Even then, given that most alfalfa is harvested and fed to cows in a closed system, most of impact here is simply the fact that Roundup Ready alfalfa will not be available to plant for a year or two. 

The Obligatory Soybean Rust Update 

        Soybean rust was detected on kudzu in southern Louisiana on June 5th.  Rust has now been found on kudzu in two parishes in Louisiana.  The incidence and severity of the disease at the initial site has increased significantly since it was first found on May 8.  Weather conditions in this area are favorable for continued development of the disease.  Soybean rust was also detected in a small patch of kudzu in eastern Texas on June 2.  This is currently the only known active rust site in Texas.  There are currently eight counties in Florida with active rust sites.  It’s relatively easy to keep track of soybean rust activity and detections by accessing the USDA’s monitoring web site at:  http://www.sbrusa.net/

Alfalfa Cutting Height 

        There seems to be a lot of variation in how high alfalfa fields are cut.  For first cutting it may just be a function of how much lodged material is in the field and the difficultly that presents in leaving a short stubble.  In some cases higher cutting heights may be needed to avoid rocks.  In the past several years there have been several research studies looking at the impact of cutting height on alfalfa yield and quality.  Interestingly, each of these studies has shown that total season dry matter yield increases about 500 lbs. per acre for each 1-inch reduction in cutting height.  Of course this yield gain will be accompanied by slightly lower forage quality, but 500 lbs. is a lot of feed to leave on the table.  Most researchers recommend that alfalfa growers strive for a 2-inch cutting height where possible.  If at all possible, implement this practice on 1st cutting where the greatest yield advantage has been seen.  In fields where plants are experiencing moisture or flooding stress, or where the crop has been cut early and frequently, root carbohydrate reserves may be low and cutting height should be adjusted upward to avoid additional stress or plant death.

If harvesting forages in the fall, growers should still leave a 4-inch or greater stubble.   

Time to start thinking leafhoppers……… 

        We've reached the point where fields will need constant monitoring from now through about early August.  Potato leafhoppers (PLH) move into Wisconsin on wind currents and storms that blow-in from the southwest U.S.  Recall that the PLH feeds on alfalfa by inserting its stylet into the alfalfa stem or leaf and starts sucking sap (carbohydrates) out of the plant.   

Research has determined that saliva from the PLH causes phloem tissue (the plant's pipeline for moving carbohydrates from the leaves to the roots) to compress and restrict flow within the tubes.  It's thought that stem feeding, and the subsequent build-up of leaf sugars because of phloem tissue closure, is actually more responsible for the symptomatic leaf yellowing (sometimes referred to as hopperburn) than the leaf feeding.  The only method to determine if fields are infested with threshold levels of PLH is to use a sweep net.  Once leaf yellowing is visible, the damage has already been done. 

        Heavy infestations of PLH can impact both plant growth and persistence.  In one study at Iowa State University, PLH-infested field plots matured 30% slower than uninfested plots. The amount of yield loss depends largely on the level of infestation (how many) and when the little guys moved into the stand.  Based on these two factors, research studies have validated yield losses from 0 to 95%.