Wisconsin Winter Wheat Disease Update – June 26, 2018

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Fusarium head blight of winter wheat

The Wisconsin Field Crops Pathology crew has scouted and rated all winter wheat variety trials across the wheat-growing region of the state. We have also looked at commercial fields for disease in the region. In general leaf diseases will be of minimal impact this season. We have observed a little Septoria leaf blotch in some fields in the lower canopy. However, this pathogen will not limit yield this season, as it has not reached the flag leaf yet. We have also not observed any stripe rust this season. As I mentioned in previous posts, the winter was cold enough with minimal snow cover, which didn’t allow the stripe rust pathogen to overwinter in the region. Subsequent spread from the southern states north, was also not fast enough to reach the crop in Wisconsin to impact yield. If stripe rust does arrive this season, it will not impact yield. Leaf rust was observed at the Arlington (south-central Wisconsin) location. However, it was at very low incidence and severity and will likely not impact yield on most varieties in the state.

Figure 2. Fusarium head blight index of winter wheat in small plots where fungicide programs were used in 2014.

Fusarium head blight (FHB; scab) has been observed at all locations visited. Incidence and severity is highly variable based on location. At the Sharon (southern Wisconsin) and Arlington locations, FHB could be found in some plots at incidence levels as high as 50% with 50% severity. Many plots had low levels of FHB, thus the average levels at these locations was around 10% incidence with severity levels of around 20%. As we moved north and east in Wisconsin, FHB was at much lower incidence and severity levels. Incidence averaged 5%-10% with severity around 15% at the Chilton and Fond du Lac locations. Commercial fields that we have scouted in these regions fall within these same averages.

Figure 3. Vomitoxin levels of finished grain from winter wheat small plots where fungicide programs were used in 2014.

While I don’t think the FHB epidemic in 2018 will be as bad as 2015, I think it is important to scout fields and understand the levels of FHB present. It will also be important to test finished grain for vomitoxin or DON. Often, the level of visible FHB damage does not reflect the vomitoxin levels of harvested grain. This happened in some fields in 2014, including a research trial that we had at the Arlington location. FHB index levels on heads in the field were very low across all treatments in our research trials that year (Fig. 2). However, when the finished grain was tested for vomitoxin, levels were quite high (Fig. 3). There are a number of factors that can contribute to this phenomenon, including time of infection, varieties, weather, and treatment. The point is, be sure this doesn’t happen to you. Scout AND have finished grain tested so you aren’t surprised at the elevator!

Wisconsin Winter Wheat Disease Update – June 6, 2018

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

The Wisconsin Field Crops Pathology Team has been busy scouting and rating diseases of winter wheat this past week across the major wheat growing region of the state. To be honest, it has been pretty boring for our group. We have seen virtually no disease in uniform variety trials or in production fields. This is good news for farmers, for sure.

We have not yet confirmed any stripe rust infections in the state of Wisconsin, this season. Reports from farmers and consultants are also consistent with our observations. This is a considerable change from last season, when we found our first stripe rust pustules at the end of March. This early epidemic in 2017 resulted in some considerable yield loss from stripe rust on winter wheat. Definitely not the case this season. We have also seen extremely low levels of Septoria leaf blotch in the lower portions of the canopy on some varieties. Cool dry weather is preventing this disease from really moving up the canopy. No other foliar diseases have been confirmed on winter wheat this season.

As for the Fusarium head blight (FHB; scab) situation, risk as calculated by the Fusarium Risk Tool, has dissipated over the past week. Two weeks ago, risk of FHB had been estimated to be high on susceptible cultivars. However, cool dry weather has driven the risk to low levels across much of the major wheat production area of Wisconsin. Risk is high still along the Lake Michigan shore and up into Door County. Also elevated and high risk are estimated in Northwest Wisconsin on susceptible cultivars. The situation should be monitored closely in these areas on any crop heading into anthesis. Most of the wheat we have looked at across the southern, south-central, and north-eastern wheat production area of the state is through anthesis or will be by the end of the week. The FHB risk is forecast to be low through this period, in these areas. We will begin scouting for FHB damage in the next week or so, but we anticipate FHB to be mostly low in many areas, with some isolated pockets of higher levels.

It is important to continue scouting over the next couple of weeks. We are transitioning away form making fungicide spray decisions, but it is important to determine the level of FHB present in a particular field, so that proper harvest preparations can be made. We will continue to update you on what we find over the next couple of weeks. However, this is the lowest level of disease on winter wheat I have seen since I have been in Wisconsin. Scout, Scout, Scout!

Wisconsin Winter Wheat Disease Update – May 30, 2018

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Warm weather last week, which continued into this week, has pushed the winter wheat crop in Wisconsin toward heading. Most varieties planted in the southern or south-central region of Wisconsin are heading, with full emergence and anthesis (flowering) beginning by the end of the week. We suspect that winter wheat in the northern and northeastern portions of the Wisconsin wheat belt to not be far behind.

Now is the time to consider your Fusarium head blight (FHB; scab) management strategy. Weather late last week had driven the FHB risk on the Fusarium Head Blight Prediction Center to a high level for susceptible varieties. Extremely hot and dry weather has forced the risk back to “low” today. However, 72 hour forecasts show risk increasing to medium in much of the wheat belt with high risk in isolated pockets on susceptible varieties (see figure). Rain today, with continued humidity and temperatures in the 80s F for the rest of the week, will keep risk elevated. Areas near the Lake Michigan shore will likely be at high risk.

A fungicide may be needed especially on susceptible cultivars to control FHB and reduce DON (vomitoxin) contamination. The fungicides Prosaro or Caramba have both performed well on FHB in Wisconsin. Timing of application of these products is critical. I would urge you to wait until anthesis has begun in your field before applying. We have observed poor control where application of these effective fungicides were made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed 4-5 days after the beginning of anthesis, compared to applications at the start of anthesis. Data from a fungicide efficacy trial to support this observation can be found by clicking here and scrolling down to pages 16 and 17. Also, remember that application of fungicides should be made no later than 6-7 days after the start of anthesis. After this time, fungicide efficacy on FHB and DON control is much reduced.

Get out there and SCOUT, SCOUT, SCOUT and monitor the FHB Prediction Center!

Wisconsin Winter Wheat Disease Update – May 24, 2018

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

The heavy moisture we have received over the last week, combined with high temperatures in the low-to-mid 80s F this week have pushed winter wheat growth stages. We have seen rapid stem elongation with flag leaves emerging in some fields in the southern and south central regions of Wisconsin. We continue to find wheat with little foliar disease. However, we are entering a critical time to make our first important fungicide decision related to protecting emerging flag leaves from foliar disease. Continue to scout. Weather has been conducive for some foliar diseases. However, wheat continues to remain “clean” then hold your fungicide application until anthesis.

Given the heat this week, I suspect that heads will be emerging for some varieties in the southern region over the next week or so, with anthesis to closely follow. The decision to apply fungicide will be critical at this time. Considering the wet weather and warm temperatures the “pump is primed” for Fusarium head blight (FHB; scab). The Fusarium Head Blight Prediction Center currently has the FHB risk at medium to high in the south, south-central and eastern portions of the wheat belt (See Figure). This situation needs to be monitored closely over the next couple of weeks as fields enter the anthesis growth stage. The weather outlook appears to be very humid, wet, and warm, which will only increase the risk of FHB.

A fungicide may be needed especially on susceptible cultivars to control FHB and reduce DON (vomitoxin) contamination. The fungicides Prosaro or Caramba have both performed well on FHB in Wisconsin. Timing of application of these products is critical. I would urge you to wait until anthesis has begun in your field before applying. We have observed poor control where application of these effective fungicides were made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed 4-5 days after the beginning of anthesis, compared to applications at the start of anthesis. Data from a fungicide efficacy trial to support this observation can be found by clicking here and scrolling down to pages 16 and 17. Also, remember that application of fungicides should be made no later than 6-7 days after the start of anthesis. After this time, fungicide efficacy on FHB and DON control is much reduced.

Get out there and SCOUT, SCOUT, SCOUT and monitor the FHB Prediction Center!

Wisconsin Winter Wheat Disease Update – May 21, 2018

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Winter wheat in the Uniform Variety Trial located in Sharon, Wisconsin in 2018

The Wisconsin Field Crops Pathology scouted winter wheat in the uniform variety trials located in Sharon and Arlington, Wisconsin late last week. The crop was jointing at both locations. The crop looks very good. We found no disease at either location. At this time last year we already had a significant epidemic of rust started across southern Wisconsin. Thus, the winter wheat crop is looking much better than this time last year, when it comes to the disease situation. We also took a quick look at a couple of production fields in the area and those also appear to be clean. We have also received some reports of wheat conditions around the Fond du Lac area. Wheat is reported to look very good there as well with no disease. We will try to also scout uniform variety trials in those locations in the next few days.

Despite good news, weather has been conducive for the development of foliar disease the last few days. I would encourage folks to be diligent in scouting. I would expect flag leaf emergence in the next 1-2 weeks across the winter wheat growing region of the state. We will be entering a very important time to make a decision about your first fungicide application. Considering the current agricultural economy, the decision to spray fungicide is going to be critical to try to break even this year. I would hold off as close to the anthesis growth stage to “pull the trigger” as you can wait. This will help maximize fungicide use to control both of the major diseases of wheat that we see in Wisconsin, stripe rust and Fusarium head blight (FHB; scab). However, if stripe rust shows up after flag leaf emergence, it might be necessary to apply a fungicide before anthesis to control a rust epidemic, especially on susceptible varieties. Based on previous research conducted by our laboratory in Wisconsin, we know that an application of fungicide that closely coincides with the start of the rust epidemic can be very effective in preserving yield on susceptible and moderate susceptible varieties. Many fungicides are effective in controlling stripe rust, including the industry leaders used for FHB control, Prosaro and Caramba. Therefore, if rust doesn’t show up in your field before anthesis occurs, you can effectively use Prosaro and Caramba to control both FHB and a late stripe rust epidemic. The best case scenario would be to only have to spray fungicide once this season. However, there is still much time left, so diligent scouting is critical to make the best decision. Get out there and SCOUT, SCOUT, SCOUT!

Wisconsin Winter Wheat Disease Update – April 17, 2018

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Assistant Field Researcher, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Winter wheat greening up after winter.

The Wisconsin Field Crops Pathology crew scouted the winter wheat uniform variety trials located in Sharon, Wisconsin late last week (April 12, 2018) prior to the latest snow storm. This is our most southerly location (near the IL state line), and is often a good early indicator of disease issues for Wisconsin. Wheat was trying to green up a bit, but the latest snow fall will surely set the crop back. With more snow in the forecast for April 18, 2018 it will be some time before we can scout wheat again for disease. That is the bad news. The good news is that we did not find any diseases.

With numerous reports of active stripe rust from states in the Mid-south we were concerned that early stripe rust might be present. We scouted known varieties to be susceptible, with no foliar symptoms apparent. You will remember in 2017, we identified active stripe rust very early in Wisconsin. This was due to overwintering of Puccinia striiformis inoculum from active infections that started in the fall of 2016. We suspect that warmer winter conditions in the 2016-2017 field season allowed P. striiformis to overwinter. Sharma-Poudyal et al. (2014) reported models that predict overwintering of P. striiformis when the 30-day average low temperatures are 14F or above with snow cover, or 21F or above without snow cover.

Figure 2. Average 30-day low temperatures, 2016-2017 30-day average low temperatures, and 2017-2018 30-day average low temperatures and P. striiformis survival thresholds under snow cover and without snow cover for Clinton, Wisconsin.

Using these thresholds and data from US Climate Data (https://www.usclimatedata.com/) for Clinton, Wisconsin (very close to our research site) in the 2016-2017 field season, we found that the under-snow-cover threshold was not below the 14F mark (Fig. 2). These warm conditions in 2016-2017 likely resulted in overwintering of inoculum at this location during last season. Using the same temperature thresholds and looking at 30-day average low temperatures for the 2017-2018 field season, we find that low temperatures where much more seasonable and were well below even the under-snow-cover threshold in January 2018 (Fig. 2). Thus, the risk for overwintering of P. striiformis inoculum in far southern Wisconsin is low this season. Even if active P. striiformis infections were found in fall of 2017, the likelihood it survived the winter was unlikely; especially considering the low temperatures in January of 2018 with minimal snow cover at this site during that time.

We will continue to scout winter wheat fields once snow melts. I would encourage others to get out and scout once the weather improves. Be sure to pay close attention to any winter wheat varieties that are known to be susceptible to stripe rust.

Literature cited:

Sharma-Poudyal, D., Chen, X., and Alan Rupp, R. 2014. Potential oversummering and overwintering regions for the wheat stripe rust pathogen in the contiguous United States. Int J Biometeorol. 58:987-997.

 

 

Wisconsin Winter Wheat Disease Update – June 30, 2017

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Stripe rust in a “striped pattern” on winter wheat leaves.

Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin-Madison

The Wisconsin Field Crops Pathology team has nearly finished all of our assessments of wheat and wheat disease for the year in Wisconsin. Winter wheat is well on its way to maturing. The few spring wheat acres we have seen have mostly completed anthesis throughout much of the state, with just a few late-planted locations still completing anthesis.

Overall, the spring 2017 wheat season can be defined mostly by the widespread presence of stripe rust. We have been in fields where stripe rust has caused significant widespread damage on susceptible varieties that were not treated with fungicides. We have also observed fields that either had a resistant variety, received a fungicide application, or both. These fields appear to be doing quite well and the crop will yield well. Clearly areas where we suspect that there was overwintering of the stripe rust pathogen, saw the occurrence of the epidemic very early, resulting in quick spread of stripe rust this season. We have completed rating of stripe rust in the wheat variety trials in Wisconsin and these data will be published later this year in the variety performance report. I would encourage you to study these results carefully and choose varieties that performed well in your area and had low levels of stripe rust. This is the second year in a row that we have had a substantial stripe rust epidemic and choosing resistant varieties is a cheap method of stripe rust management.

We have also been looking for Fusarium head blight (FHB or scab) in commercial fields and variety trials. For a second year in a row, FHB incidence and severity is extremely low statewide. In many fields we struggle to find even one symptomatic head. Fusarium head blight incidence in the far southwest part of the state is nearly undetectable and approaches about 1% incidence in fields in the north-central and northeastern portions of the state. I expect that DON (vomitoxin) levels will be relatively low in finished grain in Wisconsin, this season. The low level os FHB in winter wheat this season is likely due to the unseasonably hot, dry weather we had in early June, which coincided with anthesis in many wheat fields. This type of weather is not conducive for the fungus and likely resulted in very few successful infection events.

Other diseases have been extremely hard to find. We have seen some fields with low levels of Septoria/Stagonospora, but in general these epidemics will not limit yield to a significant extent. Powdery mildew can be found infrequently on a few plants in some fields. In the southern portion of the state, we were able to find some leaf rust just this week. The arrival of leaf rust is likely too late to affect yield this season. We have not observed any stem rust in our scouting trips to commercial fields or in variety trials.

 

Wisconsin Winter Wheat Disease Update – June 2, 2017

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Fusarium Head Blight Prediction Center Risk Map – June 2, 2017

Many winter wheat varieties in Wisconsin are headed out and at, or will be at, anthesis (flowering) this weekend. Currently, the Fusarium Head Blight Prediction Center is ranking much of the primary winter wheat growing area of Wisconsin at medium risk with many pockets of high risk for FHB on susceptible varieties (Fig. 1). Warm temperatures and the threat of rain this weekend will make conditions further favorable for FHB. In addition, stripe rust is quickly increasing in many fields on susceptible varieties. I have observed 20% stripe rust severity on flag leaves in several fields with high incidence across those fields.

The primary fungicides for control of FHB are Caramba and Prosaro. These same products are rated as “excellent” on stripe rust. I would urge you to verify anthesis has begun in your field before applying either product. We have observed poor control of FHB where application of these effective fungicides was made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed 4-5 days after the beginning of anthesis, compared to applications at the start of anthesis. Also, remember that application of fungicides should be made no later than 6-7 days after the start of anthesis. After this time, fungicide efficacy on FHB is much reduced. Finally, DO NOT use any fungicide products that contain a strobilurin fungicide after the “boot” stage in wheat. Some studies have demonstrated that using strobilurin fungicides at, or after heading, can result in increased vomitoxin (DON) levels in finished grain. Get out there and SCOUT, SCOUT, SCOUT!

Wisconsin Winter Wheat Disease Update – May 28, 2017

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. Severe stripe rust on winter wheat prior to head emergence.

The Wisconsin Field Crops Pathology crew spent some time this past week scouting wheat and rating wheat variety trial plots, between planting soybeans and dodging rain storms. Despite the challenging week, the crew was able to get around to several sites and take a look at winter wheat. Wheat ranges from fully emerged flag leaf to emerging heads across the sites visited. As predicted, stripe rust is progressing to epidemic levels on susceptible and moderately susceptible varieties (Fig. 1). We were able to find many plots with stripe rust on the L2 leaf (leaf immediately below the flag leaf) with some varieties already showing 20% or more severity on flag leaves (Fig. 2). We were also able to find many varieties still showing no symptoms of stripe rust. We also have had several reports of disease-free winter wheat across the state. Further inquiry suggests that many did their homework last summer and fall, and chose varieties with excellent stripe rust resistance. This will more than pay for itself this season in fungicide spray savings.

Figure 2. Stripe rust on a flag leaf of winter wheat.

We are quickly approaching head emergence and anthesis on many varieties in the state of Wisconsin. I predict that anthesis (flowering) will take place within the next week or so in Wisconsin. Farmers should focus on making a decision on fungicide application to control Fusarium head blight (FHB or scab). At this point, I think farmers should hold off on a fungicide application specifically for stripe rust. The major focus for fungicide application on winter wheat in Wisconsin should shift to managing FHB. With this said, the two primary products that have performed well in Wisconsin for FHB, also perform well on stripe rust and are ranked excellent in the Small Grains Fungicide Efficacy Table. This means that spraying for FHB will also control stripe rust, as long as the stripe rust epidemic has not advanced to high levels on the flag leaves. Currently, the Fusarium Head Blight Prediction Center is ranking much of the primary winter wheat growing area of Wisconsin at medium-to-high risk for FHB on susceptible varieties (Fig. 3). Plenty of rain and adequate temperatures are making conditions ripe for FHB in the major wheat production area of the state.

Figure 3. Fusarium Head Blight Prediction Center Risk Map – May 28, 2017

The next 7-10 days poses a critical time to make a decision for fungicide application to control FHB and stripe rust. The primary fungicides for control of FHB are Caramba and Prosaro. I would urge you to wait until anthesis has begun in your field before applying. We have observed poor control of FHB where application of these effective fungicides was made before anthesis. In fact, we have observed improved control of FHB and lower levels of DON in finished grain where fungicide application was delayed 4-5 days after the beginning of anthesis, compared to applications at the start of anthesis. Data from a fungicide efficacy trial to support this observation can be found by clicking here and scrolling down to pages 16 and 17. Also, remember that application of fungicides should be made no later than 6-7 days after the start of anthesis. After this time, fungicide efficacy on FHB is much reduced. Finally, DO NOT use any fungicide products that contain a strobilurin fungicide after the “boot” stage in wheat. Some studies have demonstrated that using strobilurin fungicides at, or after heading, can result in increased vomitoxin (DON) levels in finished grain. Get out there and SCOUT, SCOUT, SCOUT!

Wisconsin Winter Wheat Disease Update – May 2, 2017

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Stripe rust on lower leaves of winter wheat plants at the Feekes 5 growth stage.

Brian Mueller, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin-Madison

Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

The Wisconsin Field Crops Pathology crew continues to scout wheat stands in various locations in Wisconsin. The primary disease of focus, remains stripe rust. Late last week we identified yet another stand of winter wheat with early stripe rust in a production field near Arlington, WI. The entire stand was planted to the variety Kaskaskia and had moderate levels of severity on the lower leaves (see picture). Incidence was spotty, but correlated to the greenest plants in the stand that were protected over the winter by snow cover. Other areas of the field that clearly were not insulated by snow and were further behind in growth stage, did not have visible symptoms of stripe rust. This observation reinforces the fact that stripe rust overwintered in this location during the winter of 2016/2017.

At this point in the season many growers have made their herbicide applications and either applied fungicide or held off. Growers and consultants should remain diligent in scouting for stripe rust and other diseases as the crop moves toward flag leaf emergence. As I look into my “crystal ball” I think that a decision to spray fungicide at the flag leaf growth stage is going to be critical in Wisconsin, especially on susceptible varieties. Weather has been very wet and temperatures are becoming more conducive for spread of the stripe rust pathogen. As these conditions persist, and we approach the flag leaf growth stage, a decision will need to be made to spray to control stripe rust. Remember that the flag leaf is responsible for much of the yield that a wheat plant will make. Our work in Wisconsin in 2016, demonstrated that for every 10% increase in stripe rust coverage on the  flag leaf alone, we lost almost 5.5 bu/acre in grain yield across the Wisconsin winter wheat variety trials. Thus, protecting this leaf is extremely important. On stripe rust-susceptible varieties, we have seen much benefit in flag applications to control stripe rust, especially when the pathogen is active.

Remember that there are many fungicide options for stripe rust control. Also, fungicide applications directed toward Fusarium head blight (FHB or scab) will also protect against stripe rust. So as you make your decision to spray at the flag leaf growth stage, choose a product that fits your pocketbook and consider that you might spray a strobilurin-containing product at this earlier growth stage. Later in the season, you will want to rotate to a non-strobilurin-containing product for your FHB control (Prosaro or Caramba). Hopefully we won’t have to make two applications of fungicide this year, but be prepared should the conditions necessitate this practice. Get out and scout, scout, scout!