This month’s 2023/24 U.S. corn outlook is for fractionally higher supplies and ending stocks. Corn beginning stocks are lowered 50 million bushels, as greater feed and residual use for 2022/23 more than offsets reductions in corn used for ethanol and exports. Corn production for 2023/24 is forecast up 55 million bushels as greater planted and harvested area from the June 30 Acreage report is partially offset by a 4.0-bushel reduction in yield to 177.5 bushels per acre. According to data from the National Centers for Environmental Information, harvested-area-weighted June precipitation data for the major Corn Belt states represented an extreme downward deviation from average. However, timely rainfall and cooler than normal temperatures for some of the driest parts of the Corn Belt during early July is expected to moderate the impact of June weather. For much of the crop the critical pollination period will be in the coming weeks. With supply rising fractionally and use unchanged, ending stocks are up 5 million bushels. The season-average farm price received by producers is unchanged at $4.80 per bushel.
Soybean
Soybean production is projected at 4.3 billion bushels, down 210 million on lower harvested area. Harvested area, forecast at 83.5 million acres in the June 30 Acreage report, is down 4.0 million from last month. The soybean yield forecast is unchanged at 52.0 bushels per acre. With lower production partly offset by higher beginning stocks, 2023/24 soybean supplies are reduced 185 million bushels. Soybean crush is reduced 10 million bushels reflecting a lower soybean meal domestic disappearance forecast. Soybean exports are reduced 125 million bushels to 1.85 billion on lower U.S. supplies and lower global imports. With lower supplies only partly offset by reduced use, ending stocks for 2023/24 are projected at 300 million bushels, down 50 million from last month. The U.S. season-average soybean price for 2023/24 is forecast at $12.40 per bushel, up $0.30 from last month.
Wheat
Changes this month to the 2023/24 U.S. wheat outlook increase supplies and domestic use, leave exports unchanged, and increase ending stocks. Supplies are raised on larger production, which is up 74 million bushels to 1,739 million, on higher harvested area and yields. The first 2023/24 survey-based production forecast for other spring and Durum indicates a decrease from last year. Conversely, winter wheat production is forecast higher on larger harvested area and higher yields. Gains for all wheat production are partly offset by smaller beginning stocks, which are lowered 18 million bushels to 580 million as indicated in the Grain Stocks report, issued June 30. The 2023/24 ending stocks are forecast at 592 million bushels, 30 million higher than last month. The projected season-average farm price is forecast at $7.50 per bushel, down $0.20 from last month.
Nathaniel Bruce, Farm Business Specialist, University of Delaware and Mark Townsend, Agriculture Agent Associate, University of Maryland Extension, Frederick County
June proved volatile for grain markets. To recap, the December 2023 contract rallied off its $4.90 lows from late-May, peaking at $6.29 on June 21st and has precipitously fallen back below $5.00 at the time of writing this article. As it does, the soft red winter wheat market followed suit in the September contract with a big swing from the $5.87 lows on June 1st to a high on June 26th at $7.70 only to plummet back to earth reaching $6.51 currently. No less, the November soybean market followed a similar pattern rising from $11.30 on June 1st to peaking at $13.77 on June 21st, and then tumbling back some in the last week of June only to find levity on the last day of the month.
It’s not difficult to convey the gravity of these swings: In one singular month, we saw a $1.39 gain and decline in the corn market, a $1.87 upswing and $1.19 downfall in the wheat market, and a $2.07 upswing with a $1.13 retracement followed by an $0.76 movement higher on the last trading day of the month in the soybean market.
The summary begs the questions: how can we explain the volatility of these markets and what can we do as producers to limit our risk to any further price loss?
Firstly, the phenomena we have encountered this last month can be described as the result of a “weather market”—a period of time in which traders make decisions based on current and prospective weather conditions that affect the production (supply) of a particular commodity in hopes of capturing a premium related to production risk. Put another way, this is a “supply-side” market driver as there is a risk to the volume of production.
The weather in question is that of the central United States as the region is under varying degrees of drought. The most recent USDA Drought Monitor (6/29/2023) report indicates that 53% of the contiguous United States is experiencing some level of drought. On a per crop basis the monitor indicates that 70% of corn growing regions and 63% of soybean growing regions are in some degree of drought. Reports in June indicated progressively higher levels of moisture stress in large swaths of the corn belt. As we well know, corn demands roughly an inch of rain each week when in the rapid growth stages and entering pollination. With this, traders bet on a reduction in yield for this year’s corn crop, thus raising the price through market actions.
Traders not only looked at retrospective reports like the drought monitor, but also analyzed weather forecasts for these regions. For much of the month, neither the GFS (U.S. based) nor the ECMWF (European based) weather models predicted any significant rainfall for these regions. In some instances, the models added further uncertainty as the GFS forecasted sporadic precipitation events while the ECMWF left the radar screen blank. On the ground, drought regions experienced high winds and high temperatures further drying out soils and inducing greater rates of transpiration from an already moisture-stressed crop.
With these factors at play, market participants found reason to purchase grain futures contracts or options in hopes of realizing some future increases in commodity prices. The Commodity Futures Trading Commission (CFTC) reports the commitment of traders market positions in which the non-commercial speculative entities (aka “the funds”–referring to money managers like hedge funds or mutual funds) with significant market power were in a net short position by about 60-70k contracts of corn entering the month of June. As the month progressed, the most recent report indicates that these market participants held a 100-115k net long position (As of 6/27/2023). Effectively, this means that these market participants were betting on a decline in the corn futures market at the end of May, only to quickly reverse course and bet a far larger position on an increase in the corn futures market price. There is a significant delay in the release of these reports, so it is difficult to ascertain where the funds stand after the last week in June ending in a Friday sell-off in corn and wheat. Though current estimates place fund positions back to near neutral (equal quantity of long and short positions) in corn. Traders in the wheat futures market followed a similar path to corn, while traders in the soybean futures market are currently estimated to be in a significantly long position.
The weather trading continued later into the month; price action in the last week of June saw falling prices as regions of the Midwest realized modest precipitation accumulations. No less, the GFS and ECMWF weather models agreed on additional future precipitation events thus indicating a potential for salvage of the current crop.
To cap off an already topsy-turvy last week in June and generally volatile month, the USDA released Quarterly Grain Stocks and Planted Acreage reports on Friday, June 30th. The grain stocks report followed analysts estimates, however the planted acreage report unexpectedly and significantly deviated from the market sentiments. Reported planted corn acreage rose roughly 2 million acres from a previous prediction report, and an increase of about 5% from last year. Soybean acreage fell by about 5% compared to last year, which is about 4.2 million acres lower than the average trade estimate. Markets traded this supply-side news as corn fell back to prices not seen since December of 2020. On the other hand, the soybean market is trading back to levels from mid-June.
The volatility of these markets is unmistakably high. Not only is the current implied volatility of these markets (based on options prices) higher than 60-80% of all trading days in the previous year, but trading strategies involving options require larger investments.
Figure 1. Corn 2012 vs 2023.
Marketing a crop in these conditions is undoubtedly challenging. We may look to previous years for guidance, though even this is uncertain. Analysts have likened the run-up in the grain markets to those in 2012 when a similar drought induced crop failures across the Midwest. Currently, there exists a 0.56 correlation coefficient between the 2012 December contract and the 2023 December contract (Figure 1). In truth, this exact discussion is nothing new; many marketing professionals and memorious farmers recall the drought of 2012 that spurred a dramatic run-up in the corn price reaching a peak of $8.49 on August 10th, 2012 and will refer to this observation whenever a drought emerges in the Midwest. Although, there is a correlation in prices between Dec’12 Corn and Dec’23 corn, the fundamental supply and demand picture is vastly different between 2012 and 2023 as there is nearly 4% larger Stocks-to-Use ratio in 2023 than 2012 given the current lack-luster export, feed, and ethanol demand we have experienced for the current marketing year.
Figure 2. USDA WASDE June 2012 vs. June 2023.
Other more bearish investors have noted that the current price trend is more similar to 1992 in which an early season drought induced volatility and rising prices. Contrary to 2012, the 1992 corn market saw a dramatic price decline after timely and significant rains busted the drought and produced a near trend-line crop yield.
So how does one effectively market a crop this year? The first step as always is to know the cost of production taking into actual input price figures to uncover an operation’s breakeven price and yield. Yield does play a critical role in determining these figures, though as we know yield is not the sole driver of profitability. Please refer to the University of Maryland Extension website for enterprise budget templates here: https://extension.umd.edu/programs/agriculture-food-systems/program-areas/farm-and-agribusiness-management/grain-marketing.
Certainly a next step would be to look for ways to offset future price risk. Depending on the level of familiarity, options strategies could offer additional downside protection. However, this is most commonly accomplished by forward contracting some of the new crop. At the time of writing, the soybean market continues to rise modestly above estimated cost of production figures for Central Maryland. Producers may find these prices profitable and would be well advised to limit potential downside risk.
Marketing professionals offer that producers may find shelter in short-run run-ups to sell new crop corn and stored wheat. Some analysts predict that the USDA may have to revise yield estimates lower given the potential damage done to the corn crop of the Midwest. The market may react to this revision lower, whereby the watchful marketer could capitalize on a small upward price movement. Yes it is tempting to wait for the next larger rally in the market, but waiting to find the top of the curve may prove far more risky than taking smaller profits. A wise farmer once said that he stayed in business for many years because, “I always took my profits too early.”
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/.
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.
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.
The 2023/24 U.S. corn outlook is for larger production, greater domestic use and exports, and higher ending stocks. The corn crop is projected at a record 15.3 billion bushels, up more than 10 percent from last year on increases to both area and yield. The yield projection of 181.5 bushels per acre is based on a weather-adjusted trend assuming normal planting progress and summer growing season weather, estimated using the 1988-2022 time period. With beginning stocks up slightly, total corn supplies are forecast at 16.7 billion bushels, the highest since 2017/18. Total U.S. corn use for 2023/24 is forecast to rise about 5 percent relative to a year ago on higher domestic use and exports. Food, seed, and industrial use is projected to rise 55 million bushels to 6.7 billion. Corn used for ethanol is projected to increase 1 percent, based on expectations of modest growth in motor gasoline consumption and ethanol’s inclusion rate into gasoline. Feed and residual use is projected higher on a larger crop and lower expected prices. U.S. corn exports for 2023/24 are forecast to rise 325 million bushels to 2.1 billion, as lower prices support a sharp increase in global trade following the decline seen during 2022/23. U.S. market share is expected to increase slightly albeit remain below the average of the past 5 years. Exports are higher for Argentina and Brazil, with the former reflecting a return to normal weather conditions after a drought during 2022/23. Despite a rebound in U.S. exports, Brazil is forecast to be the world’s largest exporter of corn for the second consecutive year. Exports for Ukraine are projected to decline based on lower production prospects. With total U.S. corn supply rising more than use, 2023/24 ending stocks are up 805 million bushels from last year and if realized would be the highest in absolute terms since 2016/17. Stocks would represent 15.3 percent of use, the highest since 2018/19. The season-average farm price is projected at $4.80 per bushel, down $1.80 from 2022/23.
Soybean
The 2023/24 outlook for U.S. soybeans is for higher supplies, crush, and ending stocks, and lower exports compared with 2022/23. The soybean crop is projected at 4.51 billion bushels, up 5 percent from last year’s crop mainly on higher yields. With lower beginning stocks partly offsetting increased production, soybean supplies are forecast at 4.75 billion bushels, up 4 percent from 2022/23. Total U.S. oilseed production for 2023/24 is projected at 132.8 million tons, up 6.9 million from 2022/23 mainly on higher soybean production. Production forecasts are also higher for canola, peanuts, and cottonseed. The U.S. soybean crush for 2023/24 is projected at 2.31 billion bushels, up 90 million from the 2022/23 forecast on favorable crush margins and strong demand for soybean oil as a biofuel feedstock, which is projected to increase 900 million pounds to 12.5 billion. Domestic soybean meal disappearance is forecast to increase 2 percent from 2022/23 on lower soybean meal prices and modest growth primarily in poultry production. U.S. soybean meal exports are forecast at 14.8 million short tons, leaving the U.S share of global trade slightly above the prior 5-year average. U.S. soybean exports are forecast at 1.98 billion bushels, down 40 million from 2022/23 with strong competition from increasing South American production and limited gains in global import demand. U.S. ending stocks for 2023/24 are projected at 335 million bushels, up 120 million from the revised 2022/23 forecast. Soybean and product prices are all forecast lower for 2023/24. The 2023/24 U.S. season-average soybean price is forecast at $12.10 per bushel compared with $14.20 per bushel in 2022/23.
Wheat
The 2023/24 outlook for U.S. wheat is for reduced supplies and exports, increased domestic use, and smaller stocks compared with 2022/23. U.S. wheat supplies are forecast lower than last year with smaller beginning stocks and only slightly larger production. All wheat production is projected at 1,659 million bushels, up modestly from last year on increased harvested area. However, the harvest-to-plant ratio is down from last year with above-average abandonment in Texas, Oklahoma, and Kansas. The all wheat yield, projected at 44.7 bushels per acre, is 1.8 bushels lower than last year. The first survey-based production forecast for 2023/24 winter wheat is up 2 percent from last year as higher Soft Red Winter production more than offsets a decline in Hard Red Winter and White wheat. Total 2023/24 domestic use is projected at 1,112 million bushels, up 1 percent from last year, primarily on increased feed and residual use. Exports are projected at 725 million bushels, 50 million lower than last year. Ending stocks are projected 11 percent lower than last year and the lowest in 16 years. The projected 2023/24 season-average farm price is $8.00 per bushel, down $0.85 from last year’s record.
This month’s ‘22/23 U.S. corn outlook is for reductions to imports and food, seed, and industrial (FSI) use, with unchanged ending stocks. Corn imports are lowered 10 million bushels based on observed trade to date. Feed and residual use is unchanged at 5.275 billion based on indicated disappearance during the December-February quarter. FSI is lowered 10 million bushels reflecting cuts to corn used for glucose and dextrose and starch. With supply and use falling by the same amount, ending stocks are unchanged at 1.342 billion bu. The season-average price is unchanged at $6.60 per bu.
Soybeans
U.S. soybean supply and use forecasts for ‘22/23 are unchanged relative to last month. Soybean and soybean meal prices are also unchanged. The soybean oil price is projected at 64.0 cents per pound, down 2 cents. Global ‘22/23 soybean supply and demand forecasts include lower production, crush, and exports. Global soybean production is reduced 5.5 million tons to 369.6 million. Lower crops for Argentina and Uruguay are partly offset by higher production for Brazil. Soybean production for Argentina is lowered 6.0 million tons to 27.0 million on hot and dry weather conditions through March. Uruguay production is lowered 0.9 million tons to 1.2 million on a lower harvested area and yield. Partly offsetting is higher production for Brazil, increased 1.0 million tons to 154.0 million on higher area. Soybean crush is lowered on reduced supplies and slow pace to date for Argentina, China, Bangladesh, Pakistan, and Egypt. Crush for Argentina is reduced 3.3 million tons to 32.0 million leading to lower product exports. Partly offsetting is higher crush and higher soybean oil and meal exports for Brazil. Soybean exports are lowered 0.4 million tons to 168.0 million on lower exports for Uruguay. Imports are lowered for Bangladesh, Egypt, and Pakistan and raised for Argentina. Soybean ending stocks are raised fractionally with higher stocks for China and Brazil that are mostly offset by lower stocks for Argentina.
Wheat
The outlook for ‘22/23 U.S. wheat this month is for slightly higher supplies, reduced domestic use, unchanged exports, and increased ending stocks. Supplies are raised 5 million bushels on higher imports, based on the pace of Census imports reported to date. Domestic use is lowered 25 million bushels on reduced feed and residual use, which is decreased to 55 million. The downward revision is based on the implied disappearance for the second and third quarters indicated in the NASS Grain Stocks report. Wheat exports remain at 775 million bushels but there are offsetting by-class changes for White and Hard Red Spring exports. Projected ‘22/23 ending stocks are raised 30 million bushels to 598 million but are still 14% below last year. The ‘22/23 season-average farm price is forecast $0.10 per bushel lower at $8.90, based on NASS prices reported to date and expectations for cash prices for the remainder of ‘22/23. The global wheat outlook for ‘22/23 is for increased supplies, higher consumption, and reduced trade and stocks. Supplies are raised 0.7 million tons to 1,061.1 million, primarily on higher beginning stocks for Syria and increased production for Ethiopia. Global consumption is increased 2.9 million tons to 796.1 million, mainly on higher food, seed, and industrial use for India, and increased feed and residual use for China and the EU. World trade is lowered 1.2 million tons to 212.7 million on reduced exports by the EU, Argentina, and Brazil more than offsetting increases for Russia and Ukraine. China’s wheat imports are raised 2.0 million tons to 12.0 million, which would be the highest imports for China since 1995/96. China’s imports are raised on strong imports to date, particularly from Australia; China is now the leading 2022/23 global wheat importer. Projected 2022/23 world ending stocks are lowered 2.1 million tons to 265.1 million, the lowest since 2015/16. This month, India, the Philippines, and Ukraine are projected to have lower stocks, more than offsetting increases for Syria, the EU, and the United States.
Galen Dively, Professor Emeritus | galen@umd.edu University of Maryland, College Park
Listed below are the corn trait packages to make it easier to understand seed guides, sales material and bag tags. It is an abbreviated version of the Bt trait table plus related extension materials free online at: https://www.texasinsects.org/bt-corn-trait-table.html. Information listed Includes the name of each trait package, bag tag code, Bt toxins expressed (Cry1 types and Vip3A for caterpillars, Cry3 types for rootworms), refuge requirement (RIB=% refuge in the bag or REF=% structured refuge) and herbicide tolerance (GLY= glyphosate /Roundup-Ready, LL=glufosinate/Liberty Link, 2,4D or group 1 ‘fops’ type herbicides). Note that older trait packages, with limited or no commercial availability, are listed, so you can look back and interpret previous year’s planting records, seed guides, and research results.
The widely adopted use of Bt corn has resulted in major benefits to growers and the general public. However, resistance evolution in target insect populations has become a major threat to the sustainability of these crops. In some parts of the US Corn Belt, western corn rootworm rapidly adapted to Bt corn, and currently, some populations show resistance to all commercially available Cry3 traits. The high dose expression of Cry1 and Cry2 traits continues to provide excellent control and areawide suppression of the European corn borer in the US; however, the first case of resistance to the Cry1F toxin was reported in Nova Scotia in 2018 and resistance to other Cry toxins was recently confirmed in several eastern Canadian provinces. For corn earworm, we now have widespread field-evolved resistance to all Cry toxins in Bt corn. However, the Vip3A trait still provides excellent protection against this pest but studies show early stages of resistance developing since 2017, mainly in the southern states. Fall armyworm has been targeted by the Cry1F toxin since 2003, without any evidence of field-evolved resistance until 2010 when widespread control failures in Bt corn were reported in Puerto Rico and recent studies show high levels of resistance in several southeastern U.S. states.
Maria Cramer, Graduate Student and Kelly Hamby, Entomology Specialist Department of Entomology, University of Maryland, College Park
Recently planted field crops may be at risk from slug damage due to the heavy rains and cooler temperatures we have experienced in the mid-Atlantic from the end of April into the beginning of May. Therefore, the UMD fact sheet “Managing Slugs in Field Crops Using IPM Principles” may be of interest. This fact sheet summarizes the most up-to-date research on managing slugs in our area. Highlights include:
Identify the pest and monitor. Make sure the issue is slugs. If it is cool and overcast you may find slugs (Figure 1A+B) or slug eggs (Figure 2) in crop residue. Otherwise, as they are nocturnal, you may only find their damage on plants (Figure 3A+B). Corn is generally tolerant to defoliation, while soybeans are at risk if the growing point of the plant is damaged.
Prevent. If you have not planted yet and if possible, use row cleaners and adjust the planter so that the seed slot fully closes to reduce the risk of damage. In the long term, reducing insecticidal seed treatments may favor slug predatory insects and harvestmen.
Treat. If you use a slug bait, maximize efficacy by applying just prior to slug activity (in the afternoon or evening when weather is still and mild), but not before periods of heavy rain which may make the active ingredient less effective. Remember, the label is the law. Make sure the product you use is registered in your state and for your crop(s). Follow all application restrictions.
Figure 1. A) Gray garden slug and B) Marsh slug.Figure 2. Slug eggs in corn residue.Figure 3. A) Foliar feeding in corn with dried mucus, and B) feeding on soybean cotyledons showing characteristic pitting.
Andrew Kness, Senior Agriculture Agent | akness@umd.edu University of Maryland Extension, Harford County
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 is a foliar disease of corn caused by the fungus Phyllachora maydis and we confirmed it for the first time in Maryland from a grower field in Harford County in 2022; however, it is likely that it has been present in fields at low levels earlier than the 2022 growing season. Weather conditions across northern Maryland and Southern PA in August and September were favorable for tar spot development and pockets of disease outbreaks were reported, leading to much discussion about the disease amongst farmers and ag service providers over the 2022-2023 winter months about what to do to manage this disease in the future.
The pathogen that causes tar spot is favored by cool, wet weather. Tar spot spores overwinter in old corn crop residue and it seems to survive our winters just fine, as demonstrated by winter survival in Pennsylvania, as well as many northern corn belt states.
Temperatures between 60-70°F, coupled with 7+ hours of leaf wetness from dew, humidity, rain, or irrigation, trigger sporulation and subsequent spore germination on susceptible corn plants. Roughly 14-21 days later, signs and symptoms of tar spot will develop on corn plants in the form of small, raised black spots that have the appearance of tar or splattered black paint (Figure 1). These spots are the reproductive structures which provide secondary inoculum that repeatedly infect more tissue for as long as temperature and moisture conditions remain conducive.
In the Midwest where tar spot has been present since 2015, yield losses have been reported upwards of 60 bushels in bad years. It is also important to note that tar spot can make corn plants senesce and dry down much faster than normal, going from green to brown in 10-14 days under optimum conditions. This can make silage harvest tricky, which is why scouting is so important.
We do not know how prevalent and severe this disease will become in Maryland, so I encourage farmers to diligently scout corn fields to get ahead of it and also to determine where the disease is distributed. Scouting will also help you determine if a fungicide application is warranted. Fortunately, most fungicides that are labeled for corn do a fairly good job of protecting against tar spot, but there is data that suggests that the two and three way mode of action (MOA) products work better than single MOA products.
Fungicides should be applied as close to disease onset as possible; for tar spot this can be tricky because it can infect corn at any growth stage and it can still have significant yield impact as late into the season as R4. University research in the corn belt has found that the best chance for an economic return on investment is a single application around VT-R1; however, there are some instances where a second application was necessary but these were only when weather conditions for tar spot remained favorable during these later reproductive growth stages.
A few things to consider for tar spot management as we go into the 2023 growing season are as follows:
Avoid highly susceptible hybrids, especially in corn-on-corn fields or if you have a field with history of tar spot. There is no complete resistance to tar spot in commercial corn hybrids, but we do know there is some variability in susceptibility. Work with your seed dealers to try to identify your best hybrids and plant them in these fields where you think tar spot may be a problem.
Tillage and residue management appears to play a minor role in the management of this disease. Tillage may slightly reduce primary inoculum, but we need to keep in mind that tar spot spores can blow in from neighboring fields; so, I would not roll out the heavy tillage and blow up your no-till system just to try managing tar spot because it will only have a marginal effect.
Corn-on-corn has a higher risk for developing tar spot, especially if the previous corn crop was infected. Rotate with other crops to break up this cycle. P. maydis only infects corn (including dent, sweet, and popcorn); all other crops are not hosts.
Hybrid maturity also plays a role in disease severity. Research from the Midwest has shown that longer maturing hybrids suffer greater yield loss than shorter maturing hybrids. This is because the longer you push the grain fill period into the cooler late summer/fall months, the more likely tar spot will infect during earlier grain fill growth stages.
Scout fields this year starting a little before tasseling through to maturity. As mentioned above, this will help you determine if a fungicide is likely to pay off or not.
We will be conducting some field trials this year looking at tar spot management in Maryland with funds from the Maryland Grain Producer’s Utilization Board. Part of this project will also include a survey of corn across the state to determine the distribution of tar spot. If you think you find tar spot in a field this year, I would be interested in knowing about it. You can call or email me (410-638-3255, akness@umd.edu), or report a sighting at corn.ipmpipe.org.
