2023 Maryland Tar Spot of Corn Research

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

Summary

Tar spot is a new foliar fungal disease of corn first discovered in the United States in 2015 and confirmed in Maryland in 2022 and was estimated to be the most significant yield-limiting disease of corn in the US in 2021 and 2022. As a new disease for our state, this project collected preliminary data on the distribution of tar spot in our state and compared the efficacy of different fungicide application timings. Through field surveys we identified and confirmed tar spot in eight Maryland Counties at a frequency of approximately 47% and at a relatively low severity rate (not exceeding 30%). These observations suggest that the tar spot pathogen can overwinter in Maryland, as it has expanded its range from two counties in 2022 to at least eight in 2023. Field evaluations of two fungicide programs: one pass program at VT and a two-pass program at VT followed by R2, we observed a significant difference in tar spot severity and plant lodging compared to the control; however, there was no difference in yield. Additional research on fungicide timing and the spread of this disease should be conducted in the future to help develop improved management recommendations.

Survey of Tar Spot Distribution in Maryland

Several fields were scouted for tar spot starting during late vegetative growth stages and frequency and intensity of scouting was increased from tassel through harvest. Initial scouting was focused in fields in Harford County near fields where tar spot was confirmed in 2022. In addition, reports were solicited from other Extension Agents and crop consultants/scouts throughout the state. Suspected positive samples were confirmed by laboratory technique and all positive samples were uploaded to the tar spot tracker map on corn.ipmpipe.org.

The first reported and confirmed incidence of tar spot in Maryland for 2023 came from a corn field in Cecil County on August 22. The second came from Carroll County on August 31, followed by Harford County on September 3. We confirmed tar spot in the additional counties of Kent and Queen Anne’s on September 19; Baltimore County on September 22; Caroline County on September 25, and Dorchester County on October 6 (Figure 1).

Figure 1. Map showing confirmed distribution of tar spot for the 2023 growing season (yellow). Map from corn.ipmpipe.org.

Several fields were scouted in Northern Harford County throughout the year surrounding fields where tar spot was confirmed in 2022. By the end of the season, tar spot was found in over 50% of these fields (9/16) at levels ranging from 2% to 25% severity (Figure 2). It was observed that tar spot severity continued to increase after black layer for as long as there was green, living tissue remaining on the plants. This increase in severity after physiological maturity does not affect yield but does make for a notably increased level of severity present at harvest and thus the potential for an increase in overwintering spores that will provide inoculum for the following year.

Figure 2. Corn leaf with approximately 10% tar spot severity. Tar spot symptoms include raised, black specks on the leaves.

An additional survey of 12 fields on Maryland’s Eastern Shore from Cecil to Queen Anne’s County was conducted on September 19. During this time, two fields were confirmed with tar spot. Severity was very low (<2%) in the field in Queen Anne’s County, and high in the field in Kent County (30%).

Altogether, tar spot was confirmed in 16 out of 34 fields (47%) scouted/reported throughout the state (Figure 3), with samples coming from as far west as Washington County (no confirmed samples) east to Cecil County (two confirmed samples) and south on the Maryland Eastern Shore as far as Dorchester County (one sample confirmed).

Figure 3. Google Earth map of fields scouted (blue markers) and confirmed (red markers) presence of tar spot. Markers are approximate locations and not precise to protect the identity of the landowner and/or farmer.

Weather conditions were favorable for tar spot on the Eastern Shore and Northern Maryland; however, severe drought conditions from Frederick County west may have prevented its widespread establishment in Western Maryland.

Based on this survey, tar spot appears to be established in all the northern counties east of Frederick and south on the Eastern shore to at least Dorchester County, at a frequency of approximately 40-50%. Judging by the confirmed occurrences in other counties in different states, it is likely that tar spot is present in more Maryland Counties than determined by this survey.

On-Farm Fungicide Trials

Fungicides are an effective management tool for foliar diseases of corn, including tar spot. Research from the Midwest has shown a positive response to fungicide applications in fields where tar spot disease severity is high. However, there is debate as to if one fungicide application made around VT is sufficient to control tar spot, as yield losses have been reported as late as R4. In 2023 we established an on-farm trial to evaluate the response to a single fungicide application compared to a two-pass program for managing tar spot in corn.

Field plots were established at a farm in Harford County, MD in a field immediately adjacent to where tar spot was found in 2022. Corn (Revere Seed ‘1307 TCRIB’) was no-till planted into soybean residue with a John Deere 1775 NT ExactEmerge™, 30-inch, 16 row planter at the rate of 35,000 seeds/acre. Rows 1, 2, 15, and 16 on the planter were shut off to create alleys between adjacent plots and to eliminate treatment overlap, as well as to ensure harvest accuracy. This resulted in 12-row plots that were between 75 and 150 feet long. Plots were arranged in the field in a randomized block with three treatments and five replicates (Figure 4).

Figure 4. Tar spot fungicide timing research plot layout.

Fungicides (Table 1) were applied at the VT and R2 growth stages using a DJI T30 drone calibrated to deliver 2.8 gallons per acre spray volume to the entire length of the 12-row plots. VT applications were made on July 12 and R2 applications were made on August 5. Trivapro 2.1 SE was used for all applications. Trivapro was selected because previous research has demonstrated that multi-mode-of-action products have the best efficacy against tar spot.

Table 1. 2023 Fungicide Treatments.

Treatment Product Name

Active Ingredient(s)

Application Rate (& Timing)
Nontreated Control N/A N/A
1X Pass Trivapro 2.1 SE

Benzovindiflupyr + Azoxystrobin + Propiconazole

13.7 fl oz/A (VT)
2X Pass Trivapro 2.1 SE

Benzovindiflupyr + Azoxystrobin + Propiconazole

13.7 fl oz/A (VT) & 13.7 fl oz/A (R2)

Foliar diseases were rated prior to fungicide application and approximately every two to three weeks following until harvest. Disease severity from tar spot was visually rated as the percent leaf area infected in the canopy from 10 random plants from the center two rows of each plot.

Lodging scores were collected at harvest by conducting a “push test” on 10 plants from the center two rows of each plot. The push test consists of pushing a corn plant approximately 30 degrees from vertical; plants that break have compromised stalk strength and were considered lodged.

Yield data were collected by harvesting 12 rows of each plot using a John Deere S780 combine on October 13, 2023. Yield data was exported from the combine monitor and RTK was used to correlate yield with plot locations since we were not able to collect individual plot weights. All yields reported are adjusted to 15.5% moisture. All data were analyzed using ANOVA and significant differences between treatments were separated using Fisher’s Least Significant Difference (LSD; α=0.10).

On-Farm Trial Results

Tar spot was first observed in the plots on August 29 present at a very low level (less than 2% severity). Overall tar spot disease severity was low throughout the season in these plots. One possible explanation for this is the early planting date, which likely allowed the corn to complete its critical reproductive growth stages before weather conditions were favorable for tar spot development.

Early disease ratings revealed a significant difference in tar spot severity (p=0.0176) in treated plots vs nontreated plots (Table 2). However, late disease ratings collected at harvest show an overall increase in tar spot severity, but no difference between treated and nontreated plots. This is likely due to the fact that fungicides can only offer around 14-21 days of protection. In this trial, the second fungicide application did not provide improved tar spot control compared to the single pass treatment; however, the single fungicide application at VT delayed tar spot infection compared to the nontreated control.

Table 2. 2023 Tar Spot Disease Rating and Harvest Data.

Treatment Tar Spot Severity (%) Lodged Plants (%) Grain Yield (bu/acre) Grain Moisture (%)
9/11/23 10/12/23
Control 3.05 a* 3.75 10.0 a 192.56 19.06
1X Pass 1.18 b 2.88   5.0 a 199.05 19.41
2X Pass 0.85 b 4.00   0.0 b 201.56 20.31
p-value 0.0176 0.4133 0.0680 0.2123 0.4343

*Treatments connected by the same letter are not significantly different from each other (α=0.10).

The control plots averaged 192.56 bu/acre with a low of 169.7 and high of 214.6; the single pass (1X pass) program yielded an average of 199.05 bu/acre with a low of 177.5 and high of 228.6 bu/acre; and the two-pass (2X pass) fungicide treatment yielded an average of 201.56 bu/acre with a low and high of 194.4 and 222.7 bu/acre, respectively. However, there are no statistically significant differences in yield between treatments (p=0.2123). Likewise, there was also no significant difference in grain moisture. Tar spot disease severity was relatively low; likely too low to impact yield in this trial, leading to no yield response.

The 2X pass fungicide program did improve standability of the crop at harvest, with 0.0% lodging, significantly better than the 1X program (5.0%) and the control (10.0%).

This work was supported by funding through the Maryland Grain Producer’s Utilization Board and in-kind support from The Mill. Special thanks to Clear Meadow Farm for their use of land and equipment making this research possible.

2022 Soybean Fungicide Trials

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

Trials were established at the Wye Research and Education Center in Queenstown, MD (WYE), Central Maryland Research and Education Center in Ellicott City, MD (CMREC), and Western Maryland Research and Education Center in Keedysville, MD (WMREC) in 2022 to assess the efficacy of select fungicides for the suppression of soybean foliar diseases. Soybean ‘MAS3521E3’ were no-till planted into soybean residue at 150,000 seeds/A on 1 Jun at WMREC and 31 May at CMREC and WYE. All plots were 30 feet long and arranged in a randomized complete block design with 5 replications. Data was collected from the center 5-ft of each plot. The trial consisted of eight foliar fungicide treatments and a non-treated control. Fungicides were applied with a backpack CO2-pressurized sprayer. Fungicides were applied at the R3 growth stage on 5 Aug at CMREC and WYE and 8 Aug at WMREC. Treatments with subsequent applications were made 14 days later. Yields were collected by harvesting the center 5-ft of each plot and adjusted to 13% moisture. Plots were harvested on 8 Nov at WYE, 18 Nov at CMREC, and 22 Nov at WMREC. Data were analyzed using ANOVA, and significant differences between treatments were separated using Fisher’s Least Significant Difference (LSD; α=0.10).

The most predominant foliar pathogen at all locations was frogeye leaf spot (Cercospora sojina); however, growing conditions were generally very favorable and no disease was observed at a ratable level. This is likely due to the weather conditions around pod fill, as well as the resistance package in the soybean variety, which has a frogeye leafspot resistance rating of 7 on a 10-point scale (10 being the most resistant). Yields were above average, and no significant differences were observed between treatments at any location. No phytotoxicity was observed with any of the fungicide treatments. Data for 2023 is being processed and will be uploaded to the Agronomy News Blog once available. This work was funded by the Maryland Soybean Board.

Treatment, rate/A

and timing

Grain Moisture (%)   Test Weight (lb)   Yield (bu/A)
WMREC CMREC WYE   WMREC CMREC WYE   WMREC CMREC WYE
Non-treated control 10.6 12.6 10.7   54.7 56.3 54.3   78.4 72.1 52.0
Headline 2.09 EC/SC, 6.0 fl oz at R3 10.5 12.2 10.5   54.7 56.5 54.4   91.0 74.0 59.8
Veltyma 3.34 S, 7.0 fl oz at R3 10.5 12.5 10.5   54.2 56.5 54.3   90.3 72.0 70.9
Miravis Top 1.67 SC, 13.7 fl oz at R3 10.6 12.2 10.5   55.4 54.0 54.3   86.5 63.0 59.2
Adastrio, 8.0 fl oz at R3 10.5 12.7 10.5   54.9 55.4 54.7   84.6 58.0 58.0
Revytek 3.33 LC, 8.0 fl oz at R3 10.6 12.4 10.4   54.9 55.2 54.3   82.3 76.1 62.9
Revytek 3.33 LC, 8.0 fl oz at R3 fb

Revytek 3.33 LC, 8.0 fl oz 14 days after R3

10.6 12.7 10.5   54.8 55.4 54.2   83.6 58.9 60.9
Lucento 4.17 CS, 5.0 fl oz at R3 10.5 12.4 10.5   54.6 55.4 54.4   83.4 67.2 62.6
Lucento 4.17 CS, 5.0 fl oz at R3 fb

Lucento 4.17 CS, 5.0 fl oz 14 days after R3

10.6 12.4 10.5   54.6 55.7 54.4   81.9 64.0 55.5
p-value 0.8716 0.3464 0.7067   0.2440 0.7375 0.9531   0.6583 0.7095 0.3133
z Means followed by the same letter are not significantly different based on Fisher’s Least Significant Difference (LSD; α=0.10).

Tar Spot Confirmed in Additional Counties in Maryland

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

During the month of September we have confirmed the presence of tar spot of corn in four additional counties in Maryland. Fields with tar spot in Queen Anne’s and Kent County were found on September 19, Baltimore County on September 22, and Caroline County on September 25, and Dorchester County on October 6. This brings the confirmed distribution from Carroll County east to Cecil and south on the shore to Dorchester County (Figure 1). In my scouting travels a few weeks ago on the eastern shore, I was able to find tar spot in two out of a dozen fields that I visited.

Figure 1. Tar spot confirmed distribution as of October 9, 2023. Map downloaded from https://corn.ipmpipe.org/tarspot/.

Note that this is the confirmed distribution—this is not to say that you will not find it outside of these reported counties; as a matter of fact, I’d be surprised if it’s not out there in several other areas across the state. As you harvest corn this fall, it might not be a bad idea to hop out of the cab and check around. Tar spot can still be visible on dry, senesced tissue. The signs of tar spot are dark black, raised spots that resemble spattered black paint (Figure 2). These spots are the reproductive structures of the fungus, Phyllachora maydis. These structures, called stromata, are embedded in the leaf tissue, are slightly raised (visible under a hand lens), and cannot be rubbed or scratched off the leaf.

Figure 2. Signs of tar spot on corn.

When you are scouting you may notice several look-alikes that can fool you. Insect frass (poop) is one that looks very similar but you can wipe the spots off the leaf. You may also notice other fungi present on senesced tissue, giving the leaves a black appearance. These fungi are not tar spot but are instead secondary decomposers—i.e. they colonize dead plant tissue. You can distinguish these fungi from tar spot by looking closely at the spots. Tar spot will be strikingly dark black against the dead tissue and slightly raised, whereas these secondary fungi are less distinct and not raised (Figure 3). Also, tar spot infections start on green tissue that is still alive, so check the few green leaves that are still present for signs.

Figure 3. Tar spot on a senesced corn leaf vs. look-a-likes. Stromata are still easily visible on dead leaves. Dull, faded/blurred spots are not tar spot.

As far as management considerations for this year and moving into 2024: tillage has varied success and generally has very little effect on tar spot. While tar spot does overwinter on old crop residue and tillage can help accelerate residue decomposition, research from the Midwest has shown highly inconsistent responses to tillage for managing tar spot. A couple of reasons for this is because tar spot can be wind-blown short distances; and with the concentration of corn fields present in many areas of the state, inoculum can blow into “clean” fields from nearby infected fields. Another reason that tillage doesn’t have a major effect is because most tillage equipment (besides a moldboard plow) leaves at least some residue on the soil surface. Those exposed crop residues can be enough to get an infection started the following year.

A more effective management tactic to consider is hybrid genetics. While there is no complete resistance to tar spot, there are hybrids that tolerate it much better than others. Using more resistant hybrids next year can help manage this disease, especially in fields where you suspect that tar spot could be an issue. In addition, you can use planting date and hybrid maturity to your advantage. The combination of early planting and a early-maturing hybrids can be used to “avoid” tar spot infections by having corn beyond its critical growth stages (VT-R2) before cooler weather sets in later in the season, which is favorable to tar spot infection.

If you find tar spot in your fields, please report it by emailing akness@umd.edu or submitting a report at https://corn.ipmpipe.org/reporting-form/.

Scout for Aphids in Small Grains

Kelly Hamby, Associate Professor and Extension Specialist, University of Maryland and
David Owens, Extension Entomologist, University of Delaware

Figure 1. Barley Yellow Dwarf patch in a field of malting barley, March 2023. Photo: David Owens, Univ. of Delaware.

Last season, aphids transmitted an unusual amount of barley yellow dwarf virus (BYDV) to wheat and barley across the Delmarva Peninsula. BYDV is particularly important when it infects plants in the fall. Fall BYDV infections can stunt plants (noticed as early as green-up, Figure 1) and cause more serious yield loss than spring infections. Our most common small grain aphid species are bird cherry oat aphid (Figure 2) and English grain aphid, although bird cherry oat aphid are associated with greater and more severe incidence of BYDV.

Figure 2. Bird cherry-oat aphids.

Historically, planting after the Hessian fly-free date (Table 1) reduced the likelihood of fall BYDV infection. However, fly-free dates were calculated more than 100 years ago, and it is now not uncommon for our first killing frosts to occur in late October or even November. Long falls with milder weather allow more time for aphids to colonize fields and potentially transmit the virus. Small grains varieties vary in their susceptibility to BYDV, and planting varieties with at least some tolerance can help. Unfortunately, resistant varieties are not available in barley. Finally, monitoring and managing the aphid vectors may be necessary.

Identifying bird cherry-oat aphid: A magnifying hand lens is required to identify aphids. Bird cherry-oat aphid ranges from orange green to olive green to greenish black. Wingless individuals typically have a reddish orange patch around the base of the cornicles (tail pipes). Winged individuals tend to be very dark. Their legs, cornicles, and antennae are similar in color to their bodies and medium in size.

Monitoring and thresholds: Typically, monitoring aphids in the fall and at green-up provides the best chance of identifying and mitigating BYDV risk. Scout ten locations per field avoiding field margins and look at 1 ft of row in each, making sure to look at the crown (at or below ground level), at the stem, and on the undersides of leaves. English grain aphids tend to feed on the uppermost portions of the plants while bird cherry oat aphids tend to cluster on the lower portions, especially in barley.

University extension threshold recommendations vary by region. In southern states, 6 aphids/row-ft is considered justification for a treatment in the fall. North Carolina uses a threshold of 20 aphids/row-ft where BYDV has been a problem and cold weather is not in the 7 day forecast. For other small grains, consider increasing the threshold to 25-50 aphids per foot of row.

In 2022, one of the malting barley fields sampled averaged 17 aphids per row-ft in early November. Because of unusually warm winter weather in which average temperatures were greater than 38 degrees, aphid populations peaked in one field at 235 aphids per row-ft that had averaged 1.8 per row-ft in November. This highlights the need to regularly monitor aphid populations during periods of mild weather.

Natural enemies: A number of natural enemies feed upon or parasitize aphids and they often do a good job keeping aphid populations down. One natural enemy per 50-100 aphids should be sufficient to control aphid populations. In addition, they are good at finding aphids even when their populations are low. Small wasps that develop within aphids leaving behind “mummy” aphids (Figure 3A), lady beetles, lacewing larvae (Figure 3B), and flower fly larvae (Figure 3C) are especially common aphid natural enemies. Insecticides will also kill these natural enemies.

Figure 3. Aphid natural enemies A) parasitoid wasp and golden or tan colored “mummy” aphids, B) lacewing larva eating aphids, C) flower fly larva eating aphids. Images: David Cappaert, Bugwood.org.

Insecticides: Seed treatments (e.g., Cruiser, Gaucho) provide some protection from fall aphids, but do not continue to provide protection into the spring and are not economic in years where aphids do not occur. Due to the differences in economics and BYDV susceptibility of malting barley varieties, seed treatments may be more useful than in feed barley or wheat. We generally recommend a foliar insecticide when aphid populations reach threshold. Small grain aphids are generally quite susceptible to insecticides. Pyrethroid products (e.g., Warrior) or a pyrethroid-neonicotinoid mix (e.g., Endigo, labeled for barley only) work well for aphid control.

 

Table 1. Hessian fly-free dates for Maryland and Delaware counties

State County Date
Maryland Allegany Sept. 27
Anne Arundel Oct. 7
Baltimore Oct. 2
Calvert Oct. 8
Caroline Oct. 7
Carroll Sept. 28
Cecil Oct. 3
Charles Oct. 8
Dorchester Oct. 9
Frederick Oct. 2
Garrett Sept. 20
Harford Oct. 1
Howard Oct. 2
Kent Oct. 6
Montgomery Oct. 4
Prince George’s Oct. 7
Queen Anne’s Oct. 7
Somerset Oct. 10
St. Mary’s Oct. 9
Talbot Oct. 8
Washington Oct. 1
Wicomico Oct. 10
Worcester Oct. 11
Delaware Kent Oct. 8
New Castle Oct. 3
Sussex Oct. 10

More information:

Kleczewski, N., Cissel, B., Whalen, J. 2016. Barley Yellow Dwarf Management in Small Grains. http://cdn.extension.udel.edu/wp-content/uploads/2015/10/14051904/BYDV-Final-Draft-9-12-16.pdf.

Flanders, K., Herbert, A., Buntin, D., Johnson, D., Bowen, K., Murphy, J. F., Chapin, J., Hagan, A. 2006. Barley Yellow Dwarf in Small Grains in the Southeast. https://entomology.ca.uky.edu/files/efpdf1/ef150.pdf.

Owens, D. and B. Cissel. Insect Control in Small Grains (for Grain only) – 2020. https://www.udel.edu/content/dam/udelImages/canr/pdfs/extension/sustainable-agriculture/pest-management/Insect_Control_in_Small_Grains_2020.pdf.

 

Tar Spot Confirmed in Maryland for 2023

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

Figure 1. Regional map of tar spot of corn for the 2023 growing season. Map generated from ipmpipe.org/tarspot.

Tar spot of corn has been confirmed in Maryland for the 2023 growing season. The first report came from a field in Cecil county on August 22, followed by several additional reports in Harford and Carroll county (Figure 1).

Tar spot is a relatively new fugal disease of corn in the United States and it was confirmed for the first time in Maryland in August of 2022. As daytime and nighttime temperatures begin to decline, now is a good time to look for symptoms in your corn fields. Tar spot is favored by cooler temperatures (60-70s), as well as prolonged periods (7+ hours) of leaf wetness from rainfall, dew, or humidity. Tar spot can cause infected plants to senesce prematurely, which can adversely affect yield, especially if infection occurs early in the reproductive stages. Yield losses are not as severe if infection occurs later in the reproductive stages.

Tar spot spores overwinter in old corn crop residue and are deposited onto corn leaves via splashing rain or wind (spores are only wind-blown for very short distances). Once a spore lands on corn tissue, it will germinate and infect the plant as long as the environmental conditions remain conducive. After an incubation period of about 14-21 days, black reproductive structures, called stroma, are visible on the leaf surface (Figure 2). These structures resemble black paint or tar, hence the name “tar spot.”

Figure 2. Symptoms of tar spot on corn leaf. Black specks are the reproductive structures of the fungus.

If you find tar spot in your field, you may want to take precautions to try to prevent its spread during harvest, as you could potentially inoculate new fields by bringing infected residue into the next harvested field. If you’re harvesting an infested field, it would be a good idea to try to remove as much corn fodder off of the equipment before moving to the next field.

Preparations for managing tar spot in 2024 should start in the winter with good seed selection. If possible, choose hybrids with good tar spot resistance (there is no complete resistance); seed companies are starting to rate hybrids for their tar spot resistance/tolerance.

If you find tar spot in your field, I would be interested in knowing about it. We have a grant from the Maryland Grain Producer’s Utilization Board and one objective of the study is to determine the distribution of tar spot in Maryland. Call (410-638-3255) or email me (akness@umd.edu); or submit a report at corn.ipmpipe.org.

Maryland Regional Crop Reports: July 2023

Reports are for crop conditions up to July 6, 2023.

Western Maryland

Rain has been hit or miss here but crops are still looking good considering the erratic precipitation patterns of late. Barley harvest is complete and wheat harvest is in full swing. Disease was low but test weights and yields are still being accessed. Hay yields continue to suffer but hopefully El Nino will kick in and we will get more much needed precipitation.—Jeff Semler, Washington Co.

Central Maryland 

Frederick County has received notable rainfall in the last few weeks that has prevented potentially drastic crop condition reductions following the spell of hot and dry weather in May and June. Early corn is approaching the later stages of vegetative development, while most of the crop remains in the V8-9 stages. Soybeans are generally in notable shape, even with the early season drought. Scouted fields remain generally low in typical pests though Japanese Beetles have emerged and are maintaining a watchful eye. Soybean aphids were observed in two fields, however with more recent rains and populations well below IPM threshold values, they may remain an afterthought. Wheat harvest has progressed well with field average yields reported in the 80-110 bu/ac range. Crop moisture however has remained a touch higher than desirable. Additionally, maintain a watchful eye over earlier fields that have dried recently and have received rains–reports of low falling-numbers from local mills indicate the presence of sprouted wheat. Barley yields were outstanding as some growers noted personal bests in the 150-170 bu/ac range.—Mark Townsend, Frederick Co.

Northern Maryland

For the better part of 6 weeks, most of the region received very, very little rainfall; however, that has changed in the past two weeks where we have had multiple storms, bringing anywhere from an half inch to several inches of rain per storm. This rain was much-needed for the corn and soybean crop, as well as hay and pasture. Barley harvest wrapped up prior to the rains with very strong yields. Since wheat has matured it has been difficult to find enough dry weather to cut it. So far, wheat yields are very good with no DON but unfortunately test weights and falling numbers are declining in some areas. Earliest planted corn is in tassel, although most of it is only about 5-6’ tall. The dry April, May, and the bulk of June, coupled with relatively mild temperatures and low light intensity from the Canada wildfires, has resulted in some of the shortest corn in memory. Moisture is present as we go into tassel and silking, so hopefully we get decent pollination. Soybeans are also growing slowly but are rebounding; some early maturities are starting to flower. Regrowth on hay is very slow.—Andy Kness, Harford Co.

Upper and Mid Shore

Barley harvest finished during drought conditions with record yields. Wheat harvest has been underway for 2 weeks in between storms/ humidity/wildfire smoke. Test weight was above 60 lbs per bushel to start with, but as expected, has lowered after the stretch of rainy weather. Like barley, yields have been record breaking. While wheat harvest has been underway for 2 weeks, it’s only half complete. Even with 2 weeks of rainy weather, there are areas in the region that is still relatively dry. The storms have been spotty. Some areas have had 6 rain events with a grand total of less than an inch while other areas are over 5”.  Corn and full season beans look much better, but will need significant additional rain for decent yields. With beans blooming and corn tasseling, farmers are concerned about poor light quality resulting from the smoke filled atmosphere from wildfires up north. This is a new phenomenon for our region with very little research data available. Let’s hope for west winds with blue sky!—Jim Lewis, Caroline Co.

Lower Shore

Wheat harvest is underway. Corn maturity is varied. Early planted corn is tasseling. Corn that was planted late is still in early vegetative stages. Double-crop soybean is being planted. Full season soybean is 6-12” tall on average, in vegetative stage. There were scattered rain storms over the past couple of weeks, with some areas receiving significantly more rain than others. Non-irrigated crops in areas that had limited rain are showing signs of water stress, particularly in sandier soils. Herbicide-resistant ragweed and marestail are apparent in fields across the region.—Sarah Hirsh, Somerset Co.

Southern Maryland

We have seen dry and we’ve seen wet this month. Most areas of the region received decent rains in the last two weeks. Crops responded well. Corn is now tasseling with moisture just in time for pollination. Our corn crop is much shorter in stature than normal, but the crop overall looks good. Soybeans follow much of the same story. Early planted beans have canopied. The barley crop is now off. The wheat harvest season has been challenging, with limited harvest windows. Good news is the wheat crop has been excellent in terms of both yield and quality. Double crop beans are going in as soon as the wheat comes off. Vegetable crops are just beginning to come off. Heavy rains have hampered quality of some vegetable crops.—Ben Beale, St. Mary’s Co.

*Regions (counties):
Western: Garrett, Allegany, Washington. Central: Frederick, Montgomery, Howard. Northern: Harford, Baltimore, Carroll. Upper & Mid Shore: Cecil, Kent, Caroline, Queen Anne, Talbot. Lower Shore: Dorchester, Somerset, Wicomico. Southern: St. Mary’s, Anne Arundel, Charles, Calvert, Prince George’s

Wheat Quality Concern—Falling Numbers are Falling

Nicole Fiorellino, Extension Agronomist | nfiorell@umd.edu
University of Maryland, College Park

Figure 1. Extreme example of pre-harvest sprout in wheat. Image: Ohio State University.

2023 was shaping up to be a decent wheat season, with mild winter and minimal disease impacts this spring. Although some areas of the state were dry, there were some timely rains at the end of April to get the crop through the rest of the season. We sometimes forget that wheat thrives in much drier climates than the Northeast, and what seems dry to us was probably ideal for wheat.

As wheat harvest is currently underway in some areas of the state, the hopes of high yields and disease-free grain may now be riddled with an unseen quality blemish – falling falling numbers. Growers producing wheat for use in milling or baking are paying attention to quality measures such as falling numbers, or the activity of the alpha amylase enzyme in the grain stemming from pre-harvest sprouting. As grain begins sprouting within the head, prior to harvest, alpha amylase builds up and degrades starch, which decreases flour quality. To measure falling numbers, a slurry of grain meal and water is mixed and a plunger is dropped into the slurry, with the time measured for the plunger to drop through the slurry. High alpha amylase results in low starch, which thins the slurry and the plunger falls quicker, resulting in lower falling number measures. In short, low falling numbers equals bad quality wheat that is not suitable for milling or baking.

Causes of low falling numbers, similar to disease pressure, are somewhat out of a grower’s control and not very well understood. Some areas of the state received a respite from the dry conditions, in the form of a few days with a small amount of precipitation towards the end of June. While our corn crop happily received the moisture, this was enough rain in some areas to not only delay the beginning of wheat harvest but signal the wheat grain to break dormancy and begin to sprout. Low falling numbers may also be observed in grain that did not sprout due to a defect known as late maturity alpha amylase (LMA). This is the buildup of alpha amylase in the wheat grain triggered by cold stress during maturation. It is still unclear how to specifically define “cold stress” that causes LMA but it is yet another process that increases alpha amylase in the wheat grain, decreasing flour quality. In any given season, low falling numbers can be a result of either pre-harvest sprouting or LMA or even both conditions. Susceptibility to pre-harvest sprouting and LMA are genetically linked, but even with genetic resistance, the interaction between genetics and environmental conditions can still result in decreased falling numbers.

For the 2023 wheat crop, it is important to get wheat harvested as soon as possible. There is no way to correct for falling numbers now, but growers can make every effort to get wheat out of the field as quickly as possible to avoid exposure to additional precipitation events. While all hope is not lost and wheat with low quality can still be sold for feed, any potential premiums for producing high quality wheat will be lost. For future seasons, Maryland growers can make an effort to select early maturing wheat varieties, to hopefully expedite harvest in the spring. We know the down-season benefits of early wheat harvest, such as earlier planting and higher yields of double crop soybeans, and we are also aware of the potential risk of frost damage to early maturing wheat. However, early maturing wheat varieties may be a the best option to mitigate quality issues. While your premium for 2023 may be lost, you should begin discussing your 2024 wheat crop with your crop insurance agent now, especially if you are planning to grow high quality wheat for milling or baking. There may be coverage options available to protect you from lost premiums due to poor falling numbers, for example, so now is the time to plan accordingly for 2024.

Scout for Tar Spot in Corn

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

As many of you are aware, we confirmed tar spot for the first time in Maryland during the 2022 growing season. Tar spot is a foliar disease of corn caused by the fungus Phyllachora maydis. This disease has the potential to significantly impact yield.

Figure 1. Signs and symptoms of tar spot on corn. Black raised areas are tar spot and long rectangular grey lesions are from grey leaf spot.

Tar spot may appear in corn on any above-ground plant surface and may appear at any growth stage; however it is often not observed until late vegetative to reproductive stages. P. maydis requires cooler temperatures and moisture to infect corn. Over the past few weeks we have had relatively cool nighttime temperatures, coupled with rain (leaf wetness) and high humidity. This combination of cool temperatures and wet plants, along with low light intensity from prolonged cloud cover and smoke from wildfires to our north, could flare tar spot infections. I encourage you to scout your fields in the coming weeks to look for the raised, black lesions of tar spot (Figure 1). Research has indicated that fungicide applications around VT/R1 have the best odds of return on investment for managing tar spot; however, in some cases a second application made as late as R4 may also provide an economic benefit if weather conditions remain cool and wet. As you can see in the Fungicide Efficacy Table for Corn (next page); most fungicides do a good job of managing this disease; however, products with two and three-way modes of action tend to provide better control.

Tar spot can also cause corn to senesce and dry down very rapidly, so be aware of this if you are growing corn for silage as a tar spot infestation can take a field from above chopping moisture to well below optimum in just 10-14 days.

This year we were awarded a grant from the Maryland Grain Producer’s Utilization Board to evaluate fungicide timing for managing tar spot; data will be provided at the end of the season. A second part of this project is to get a handle on how prevalent tar spot is across Maryland. If you find tar spot in your fields, I would be interested in knowing about it. You can call, text, or email me (akness@umd.edu), or you can report a sighting at https://corn.ipmpipe.org/reporting-form/.

Corn and Soybean Fungicide Efficacy Charts

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

Each year, Extension faculty from across the US compile fungicide efficacy charts for foliar diseases of corn and soybean. These charts list the major foliar diseases of corn and soybean and the relative effectiveness of foliar fungicides for managing those diseases. Ratings are based on the latest data from field trials across the US. Use the carts to aid your selection of an effective fungicide program for your crop. Corn and soybean charts can be accessed online from the Crop Protection Network.

Maryland Regional Crop Reports: June 2023

Reports are for crop conditions up to June 1, 2023.

Western Maryland

To say we are dry would be an understatement. Corn planting is winding down and the last of the full-season beans will soon be finished up too. Barley and wheat are in full head a bit ahead of normal, whatever that is. The dry weather is a good thing for cereals as the conditions are poor for fungal growth. It will be interesting to see what effect the dry weather will have on test weight and yield. First cutting alfalfa and most of the grass hay is in the barn or silo. Rain will be important very soon for forage regrowth and corn and bean growth. The cool evenings and overnights have been the only blessing but heat is on the way.—Jeff Semler, Washington Co.

Central Maryland 

Frederick County has finished planting corn. There may be the occasional field that remains, but this is the exception. Early corn is at the V4-5 stage while later planted fields are approaching V2. Seedling diseases have been nearly non-existent in scouted fields, though wireworm pressure has been observed in both corn and soybean fields. Soybeans are 90% planted; early beans are around V2 while most are VC-V1.  The majority of the hay crop is made and in the barn. Annual weeds have emerged and are approaching a foot tall in some fields, though weed pressure has remained limited given the dry weather and resulting effective burndown applications. Second cutting alfalfa is underway, some weevil pressure had been observed in the occasional field though generally there has been relatively limited pressure. Most barley is at or near soft-dough stage, while the wheat crop has finished flowering and is moving into grain fill. Both small grain crops appear in good to great condition given the limited disease pressure.—Mark Townsend, Frederick Co.

Northern Maryland

We got through the entire month of May without any measurable precipitation. Such weather has made for great conditions for making hay, and this is one of the few times in recent memory where pretty much all of the first cutting hay crop was put up before June 1; although yields did appear to suffer in some fields due to the dry weather. 99% of the corn crop is planted and emerged, with earliest planted corn around V5-6. Almost all full-season soybeans have been planted and are anywhere from just planted to V3-4. Both corn and soybeans have yet to show wilting, but they are both growing very slowly due to the lack of rain. Fortunately we are running well below with temperatures in the 70s most of the month. Wheat is just starting to turn and appears to have very little disease pressure; we will see how the dry spring affects yield and test weight. We are hoping for a bit of rain in the coming weeks.—Andy Kness, Harford Co.

Upper and Mid Shore

Early planted corn greened up, but definitely has reduced yield potential. Later planted corn looks great- good color and uniform. Early beans are finally outgrowing slug feeding. Like corn, later beans look great. Barley harvest will begin 1st week of June. Wheat is starting to turn. There was great hay made last week. Soil conditions across the region are getting dry.—Jim Lewis, Caroline Co.

Lower Shore

Wheat and barley are drying down. Corn has been planted, and is generally around V1 to V5 stage. Most soybean has been planted and early soybean plantings have emerged. Herbicide-resistant weeds, such as common ragweed, marestail, and palmer amaranth, are starting to emerge. Scout and spray early to stay ahead on control. Some farmers have utilized late-terminated cover crops to help manage weed pressure through providing a mulch on the soil surface. Deer are prevalent in fields and causing damage on corn and soybean seedlings.—Sarah Hirsh, Somerset Co.

Southern Maryland

Temperatures finally touched the 80°F mark this week. Cooler temperatures and lack of rainfall has slowed crop progress in May. Most corn fields are a kaleidoscope of yellow shades and uneven stands. Black cutworms, slugs, wireworms and seed corn maggot are active across the region. We received scattered showers last weekend that helped crop conditions improve in most areas. Soybeans follow much of the same story. Early planted beans look decent. Barley is drying down with harvest expected any day. Wheat will not be far behind. Ryegrass continues to be a challenge for producers in both burndown situations in corn and beans, as well as small grains. My thought is the cooler weather is affecting the performance of glyphosate, especially on larger plants. The pockets of glyphosate resistant ryegrass are expanding in our area as well. The drier weather has been good for making hay- we saw a lot of balers in the field last week.—Ben Beale, St. Mary’s Co.

*Regions (counties):

Western: Garrett, Allegany, Washington. Central: Frederick, Montgomery, Howard. Northern: Harford, Baltimore, Carroll. Upper & Mid Shore: Cecil, Kent, Caroline, Queen Anne, Talbot. Lower Shore: Dorchester, Somerset, Wicomico. Southern: St. Mary’s, Anne Arundel, Charles, Calvert, Prince George’s