April�s Ag Advice By April Borders I have been receiving lots of calls on wheat diseases recently and there are some real problems happening out there. This was the year of the disease in the wheat and if you didn�t spray a fungicide you have probably suffered a serious hit to your wheat yields. We have seen leaf rust, stripe rust and Septoria leaf spot just to name a few but the �big bad wolf� that we are dealing with now is Fusarium bead blight otherwise know as �scab.�
There are several things to understand about Fusarium head blight (FHB) and the fungus produces a mycotoxin called DON or vomitoxin. Heads that are infected at flowering (when most infections occur) result in white spikelets. Under the right conditions, the fungus produces DON. Later infections may result in symptomless infections where DON may or may not be present.
DON is toxic and the FDA has recommended levels that are allowed in livestock feeds. If you have scab and plan on using this crop for feed, you should test the feed for DON levels. Send feed samples to ND Veterinary Diagnostic Laboratory, ND State University, Fargo, ND 58102.
When harvesting scab infested fields, producers should turn up the fan speed on the combine. FHB or scab will cause shriveled kernels if the infection comes early in seed development. Blowing those badly shriveled (sometimes called tombstone kernels) seed out of the combine with the chaff is a good practice to reduce the grain with high levels of mycotoxins being harvested. This will reduce your harvested yield a little but you don�t want the shriveled kernels to be part of the harvest anyway. Shriveled grain typically has the highest toxin content.
Be aware that elevators will most likely be testing for vomitoxin (DON) this year and they can assess some significant dockage at times.
Dr. Marty Draper, SDSU Extension plant pathologist said, �There is a general void of knowledge about DON in straw. We often see the disease spread out of the head into the straw. Typically scab moving into the straw is expressed as a bronzing or purpling in the peduncle directly below the head. The infection may spread down the culm a few inches in most years. In general, I would expect low levels of DON in wheat straw, at most. The safety of feeding that straw is greater when it is diluted, supplemented, or blended with other forages.� Again, you should have the feed tested. The test costs $60 and provides results on several mycotoxins.
Another FYI, for your information, is the fact that soybean aphids have been found on soybeans in Turner County. These plants were V3 – V4 growth stage. So the pest is here early so you need to be out in your fields scouting and determining what level of infestations you have. There is some new information out there on threshold levels at various growth stages. You can find the information on the SDSU Plant Science home page.