Discussions and experiences related to vomitoxin, which is also referred to as DON, in corn silage continues to perplex both livestock producers and researchers. Although there are more potent mycotoxins than DON, none are more common in regions of the U.S. where corn silage is widely grown.
“Mycotoxins are secondary metabolites produced by fungi that can be toxic to plants and animals,” says Damon Smith, University of Wisconsin extension plant pathologist. “These are termed secondary metabolites as they are not produced by primary metabolism in fungi. We understand some things about secondary metabolism in fungi, but there is much left to learn,” he writes in his Badger CropDoc blog.
In corn, DON is produced primarily by a fungus called Fusarium graminearum, which is responsible for Gibberella ear rot and also Gibberella stalk or crown rot of corn.
Smith is on a mission to find some answers. During the past two growing seasons, he and his co-workers have designed and completed several field trials to see if fungicide applications effect DON concentration levels and determine if DON is preferentially accumulating in certain plant parts. In a summary of his research to date, Smith cites the following results to date:
1. DON can accumulate in both corn ears and stalks.
2. Some hybrids might be more susceptible to stalk DON accumulation than ear DON accumulation. In one trial, comparing two different hybrids, DON was higher in the ears of one and the stalks of the other.
3. DON accumulation in stalks looks to be independent from ear DON accumulation.
4. Fungicide applications may not always reduce DON, especially in years conducive for F. graminearum or when stalk infection is a primary means of DON accumulation in the corn plant. Smith notes that it might be hard to get fungicide into stalks to reduce stalk infection. Thus, DON still accumulates in the stalk portion, independent of ear infection control by fungicide applied at the R1 (silking) stage.
5. The best all-around fungicide timing when trying to reduce DON is still at R1, though this may differ depending on the product used. Smith says that this timing has the best chance of reducing DON in the ear, where DON concentrations can be high in some hybrids. He thinks earlier applications at V6 could be reducing stalk infection and subsequent DON accumulation in stalks, but more work needs to be done to confirm this.
"Mazungumzo na uzoefu unaohusiana na ""vomitoxin"" katika silage ya mahindi inaendelea kuwachanganya wazalishaji wa mifugo na watafiti." Ingawa kuna mycotoxins nyingi zaidi kuliko DON, hakuna moja ambayo ni ya kawaida zaidi katika mikoa ya Marekani ambapo silage ya mahindi hupandwa sana. "Mycotoxins ni metabolites sekondari zinazozalishwa na kuvu ambayo inaweza kuwa sumu kwa mimea na wanyama", anasema Damon Smith, Chuo Kikuu cha Wisconsin mtaalamu wa ugonjwa wa mimea. <unk>Hizi huitwa metabolites za sekondari kwa sababu hazitokezwi na kimetaboliki ya msingi katika kuvu. Tunaelewa mambo fulani kuhusu kimetaboliki ya sekondari katika kuvu, lakini kuna mengi kushoto kujifunza, <unk> anaandika katika blogu yake Badger CropDoc. Katika mahindi, DON hutengenezwa hasa na kuvu inayoitwa Fusarium graminearum, ambayo ni wajibu kwa Gibberella shingo kuoza na pia Gibberella shina au taji kuoza ya mahindi. Smith yuko katika utume wa kupata majibu fulani. Katika misimu miwili iliyopita ya kukua, yeye na wenzake wameunda na kukamilisha majaribio kadhaa ya shamba ili kuona ikiwa matumizi ya dawa za kuua wadudu huathiri viwango vya mkusanyiko wa DON na kuamua ikiwa DON inakusanya kwa upendeleo katika sehemu fulani za mmea. Katika muhtasari wa utafiti wake hadi sasa, Smith anataja matokeo yafuatayo hadi sasa: 1. DON inaweza kukusanywa katika masikio ya mahindi na shina. 2. Uwezekano wa kupata Baadhi ya mchanganyiko inaweza kuwa zaidi nyeti kwa mkusanyiko wa DON stalk kuliko mkusanyiko wa sikio DON. Katika jaribio moja, kulinganisha viumbe wawili tofauti, DON ilikuwa ya juu katika masikio ya mmoja na shina la mwingine. 3. Uwe na mtazamo wa kweli DON mkusanyiko katika shina inaonekana kuwa huru kutoka sikio DON mkusanyiko. 4. Uwe na uhakika Matumizi ya dawa ya kuua kuvu yanaweza sio kupunguza DON, haswa katika miaka inayofaa kwa F. graminearum au wakati maambukizi ya shina ni njia ya msingi ya mkusanyiko wa DON katika mmea wa mahindi. Smith anasema kwamba huenda ikawa vigumu kuingiza dawa ya kuua kuvu katika shina ili kupunguza maambukizo ya shina. Kwa hivyo, DON bado hukusanyika katika sehemu ya shina, bila kujali udhibiti wa maambukizo ya sikio na fungicide iliyotumika katika hatua ya R1. 5. Uwe na mtazamo mzuri. Wakati bora wa fungicide wakati wa kujaribu kupunguza DON bado ni R1, ingawa hii inaweza kutofautiana kulingana na bidhaa inayotumiwa. Smith anasema kwamba wakati huu una nafasi bora ya kupunguza DON katika sikio, ambapo viwango vya DON vinaweza kuwa juu katika baadhi ya mchanganyiko. "Amesema kuwa matumizi ya awali ya V6 yanaweza kupunguza maambukizi ya shina na mkusanyiko wa DON katika shina, lakini kazi zaidi inahitaji kufanywa ili kuthibitisha hili. """