April's Ag Advice By April Borders Well our winter wheat crop is over and done for the most part and it was really a mixed bag of problems. Going into the year the crop stand looked great and we all hoped that we were going to have a great crop. Then along came the problems � leaf and striped rust and the �big bad wolf� Fusarium head blight, or scab.
Dr. Bob Thaler, swine specialist at SDSU cautions producers about using scabby grain and the straw. The two most common mycotoxins we are concerned with in South Dakota are vomitoxin (DON) and zearalenone. If fed grain containing vomitoxin, pigs will vomit and then completely refuse feed. He said, �There are no real health concerns with DON besides feed refusal and no growth. Once the contaminated feed is replaced with clean feed, the pigs will start eating immediately and performance will return to normal.�
Zearalenone has estrogenic-like effects and if zearalenone is the mycotoxin present, pigs will eat it, but it then can cause reproductive problems in the females.
Grains contaminated with either mycotoxin can be fed to pigs, but it should be blended down so the total diet contains no more than one ppm of the mycotoxin. Dr. Thaler said, �The best place to feed mycotoxin infected feed is to grow-finish pigs that will not be used for replacement stock.�
The straw can also contain the mycotoxins and some wheat samples have come back from southeast South Dakota containing over 100 ppm vomitoxin so far this summer. If the straw contains vomitoxin, it is not a problem if the pigs eat it since all they�ll do is just quit eating the straw. Thaler warns that if the straw contains zearalenone, it is best not to use it for gestating sows since they are limit-fed and will often eat straw to get gut-fill. However, neither one will cause any death loss.
If you have concerns or suspect there is mycotoxins in the grain and the straw, the best thing to do is to send samples in to determine if any mycotoxins are present, and if so, at what level. Once that information is available, producers can manage around the situations.
With that all said, let�s look at these empty fields. We need to be looking at ways to control the weeds now that the wheat is harvested. The effectiveness of post-harvest weed control is influenced by production practices, environmental conditions, crop residue and many other things.
Weeds under stress are difficult to control. It�s a general rule that you can wait a maximum of 30 days after harvest to spray wheat grown as part of a three-year rotation, but if the wheat is planted without an 11 to 14-month fallow period, it should be sprayed within 15 days of harvest. Each field should be examined separately. This year some will need to be sprayed before 30 days. The key is to prevent weeds from using soil water and producing weed seeds.
Controlling volunteer wheat is especially helpful in reducing the spread of wheat streak mosaic disease. So make sure that you are considering this as you prepare to spray.
Split treatments might be an option for your particular situation. When using glyphosate products make sure that you check the label as some require surfactants to be added while others include sufficient surfactant. Also consider adding ammonium sulfate (spray grade). Ammonium sulfate is especially helpful when stress conditions are present.
Many options besides increasing herbicide rates are available for weed control after wheat harvest. Combining several options can help achieve maximum weed control. Preparing a good firm seedbed, controlling weeds in a timely manner, fertilizing if needed, seeding properly, planting during the optimum time, selecting a competitive winter hardy wheat variety and controlling weeds in the growing wheat offer the best chance of reducing weed population and vigor after harvest. Also it is important to closely watch for weed development and spray at the proper time to achieve maximum control. As always, read the label carefully and check for additional information before applying the product.
For more information, contact the Clay County Cooperative Extension Service at 677-7111.