Wheat Scab Update: Week of May 20. Wheat heads are beginning to emerge or emerged over the weekend in some locations across the state. Early-planted fields and early-maturing varieties will likely reach anthesis (flowering) this week, but most of the crop will likely reach this critical growth stage during next week (the week of May 27). The next 7 to 10 days will be very important for making decisions regarding fungicide application for scab control. The forecast is for temperatures in the upper 80s early in the week, cooling down to mid-60s and lower-70s over the weekend and early next week. There is a 30-60% chance for rain on Tuesday, Wednesday, and Thursday of this week, followed by drier conditions for the next 7 days or so. The risk for scab is currently low across the state. This is due in part to the fact that it has been cool and dry in most areas. However, if it becomes warm and humid and rains over the next several days, as the weather forecast indicates, the risk for scab will likely increase for wheat flowering later this week and over the weekend. Check the risk tool regularly and be prepared to apply Prosaro or Caramba if the risk for scab increases in your area. Remember, both of these fungicides are most effective against scab and vomitoxin when applied at flowering. If you are unable to apply the fungicide at flowering, our data suggest that applications made 2-4 days after flowering will still provide some level of scab suppression.

–Pierce Paul, Extension Plant Pathologist, Ohio State University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

The focus of the FHB prediction effort is transitioning north into KS, Central IN and IL this week. The risk of disease is currently low in most areas of the country. This low risk is a welcome change after several weeks of moderate or high risk in many states during early May. Growers in areas with flowering wheat should watch for another round of storms moving through the US this week. The risk of FHB may increase again if this weather system brings persistent high humidity and moderate temperatures.

–Erick DeWolf, Extension Plant Pathologist, Kansas State University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

The growth stage of wheat in Kansas is highly variable this year because drought conditions last fall made for delayed and patchy emergence. In general, the wheat south of Wichita is past flowering now but just west of this area the wheat is still heading in many fields. Central Kansas will be heading this week and should flower in about 7 to 10 days. The risk of severe Fusarium head blight remains low after a week of hot dry weather.  However, storms moving into the area beginning on May 18 may increase the humidity and risk of disease.

–Erick DeWolf, Extension Plant Pathologist, Kansas State University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

Wheat in southern/southwestern Oklahoma is maturing and will speed up with the warmer (>90 F) over the last couple of days. In central Oklahoma, around Stillwater and to the north, wheat is just finishing or has just past flowering and kernel development is starting. As you head to northwest  Oklahoma, wheat also is in late flowering or has just finished flowering.  Disease-wise, not a lot changed over the past week in Oklahoma. Leaf rust remained practically absent although infections in the 15-40S range were observed in Jagalene (or Jagger) guard rows in breeder plots at Stillwater.  Stripe rust is slightly more prevalent with “hot spots” being observed around Stillwater and occasional “stripes” (but not hot spots) were noted west of Enid, north of Ponca City, and north of Stillwater.   Leaf spotting diseases, barley yellow dwarf, and wheat streak mosaic (WSM) are the most commonly observed diseases in samples seen at field days and submitted to the Plant Disease and Insect Diagnostic Clinic. This past week a few samples also tested positive for High plains virus.

–Bob Hunger, Extension Plant Pathologist, Oklahoma State University

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

Most of the wheat in TN is in the milking/dough growth stage (early kernel growth stages – Feekes 11.1 to 11.2) and the window to apply fungicides has passed. Fungicides applied to manage Fusarium Head Blight (Scab) have a Pre-Harvest Interval (PHI) of 30 days, which roughly equates to 6 days after flowering as the latest application possible. Symptoms of Scab may be visible in fields 15 to 20 days after flowering, before wheat starts to mature and turn golden. With 10% or more of spikelets or heads showing symptoms DON levels (Deoxynivalenol – a mycotoxin produced by Fusarium fungi) may be problematic. For more info and images visit http://news.UTCrops.com/

–Heather Young-Kelly, Extension Plant Pathologist, University of Tennessee

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

Risk levels for FHB have returned to low for the majority of Delaware. Wheat that is heading or entering flowering will only be at risk if temperatures become favorable for infection and rain occurs. Growers are encouraged to continue to monitor their wheat as it enters flowering and apply appropriate fungicides if needed at Feekes 10.5.1 (early flowering at the beginning of anthesis). Growers have a 3-5 day window to apply fungicides after wheat has entered Feekes 10.5.1. Fungicides applied earlier or later will not provide suppression of FHB. Fungicides containing a group 11 active ingredient are not recommended for control of head scab.

–Nathan Kleczewski, Extension Specialist, University of Deleware

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

The risk of scab has returned to low in Maryland. Wheat that began to flower a few days before Mother’s day to Mother’s day is the only crop that was at risk of significant scab so far this season. The risk of scab for wheat that has not yet come into flower will depend on when they begin to flower and when and if rainfall occurs. Temperatures are expected to be favorable for the near future. Fungicides are only recommended for the crop that began to flower near and up to Mother’s day. The window for application is the day flowering begins to about 5 days later. For wheat that has not yet flowered no fungicide is required but continue to monitor this site for possible changes of risk assessment as it approaches flowering. Note symptoms of frost damage of wheat that was in flower to early dough when frost occurred will resemble scab symptoms. No fungicide will change that or protect against that.  Frost damaged wheat does not need a fungicide treatment to prevent other diseases any more than non-frosted wheat. Make fungicide decisions on the basis of disease presence or risk. No strobilurin-containing fungicide  should be used this late in the season as you risk increasing vomitoxin levels if scab does occur.

–Arv Grybauskas, Extension Plant Pathologist, University of Maryland

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

The FHB risk in much of KY has declined considerably due to sunny, dry weather. However, rain predicted for later in the week could retun us to a moderate FHB risk. If your crop has been flowering for more than 5 days, harvest restrictions for individual products will preclude you from spraying a fungicide if you have not already done so. Plus, results would be very iffy. However, fields in the east that are just now begining to flower and up to 5 days into flowering may benefit from a fungcidie application should the FHB risk increase over the next week. Research has shown that Caramba, Proline and Prosaro are the preferred products for suppressing FHB symptoms and DON contamination of grain. Tebuconazole products used alone will not perform as well as the recommended products. Any product that contains a strobilurin should not be applied when there is a significant FHB risk due to the potential to increase DON in harvested grain above that of non-treated wheat. Fungicides containing a strobilurin do not have Fusarium head blight (head scab) on the product label.

–Don Hershman, Extension Plant Pathologist, University of Kentucky

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

The risk of scab has increased to a moderate to high level for Kent and Sussex counties due to the warm weather and showers experienced over the weekend. Wheat is beginning to flower or is a few days past flowering in some areas, and near flowering in others. Fungicide applications should be considered for wheat in flower in high risk areas. Fungicides can be applied up to 5 days past the start of flowering and still provide FHB suppression.  Wheat that has not yet flowered is not susceptible. Suggested fungicides include Caramba, Prosaro, and Proline. No fungicide containing a group 11 active ingredient should be used. Examples include Headline, Quadris, and Quilt. The cooler temperatures expected throughout the week are likely to reduce FHB risk levels.

–Nathan Kleczewski, Extension Specialist, University of Deleware

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu

The FHB risk in much of central and west KY contines to be moderate. Risk is higher in east KY. Dry weather today through Wed will allow some fields to be sprayed with a scab fungicide, assuming you are not more than 5 days past the beginning of crop flowering (anthesis). If your crop has been flowering for more than 5 days, harvest restrictions for individual products will preclude you from spraying. Plus, results would be very iffy. Research has shown that Caramba, Proline and Prosaro are the preferred products for suppressing FHB symptoms and DON contamination of grain. Tebuconazole products used alone will not perform as well as the recommended products.  Any product that contains a strobilurin should not be applied when there is a significant FHB risk due to the potential to increase DON in harvested grain above that of non-treated wheat. Fungicides containing a strobilurin do not have Fusarium head blight (head scab) on the product label.

–Don Hershman, Extension Plant Pathologist, University of Kentucky

For more details, go to the FHB Risk assessment tool at http://www.wheatscab.psu.edu