Soybean Cooperative Agricultural Pest Survey: Vigilance against Potentially Invasive Species

Jaime Cummings and Ken Wise (NYS Integrated Pest Management Program), Mike Hunter, Mike Stanyard, Aaron Gabriel and Kevin Ganoe (Cornell Cooperative Extension), and Michael Dorgan (NYSDAM)

Cooperative Agriculture Pest Survey Header
 Image courtesy of Purdue University CAPS website

Annual funding in the Plant Protection Act 7721 supports the Cooperative Agricultural Pest Survey (CAPS) pest detection program, led by the USDA Animal and Plant Health Inspection Service (APHIS), to safeguard against introductions of potentially harmful plant pests and diseases.  These surveys ensure the early detection of potentially invasive species that could negatively impact U.S. agriculture and/or environmental resources.  The NYS Department of Agriculture and Markets (NYSDAM) works with APHIS to prioritize the potentially invasive species to monitor in economically important commodities in NY each year.  In 2019, NYSDAM partnered with the NYS Integrated Pest Management (IPM) program to coordinate a soybean CAPS survey to monitor for two potentially invasive moth species, as well as to expand monitoring of the soybean cyst nematode across New York soybean production areas.

The overarching goal of the CAPS program is to monitor for species that shouldn’t be here, and to confirm that they still aren’t in NY or even the U.S.  These surveys are often the result of cooperation among state and federal employees, such as APHIS pest inspectors, NYSDAM inspectors and extension specialists.  This ‘boots on the ground’ approach allows for broad coverage of the surveys across the state involving many individuals with agricultural and pest identification expertise.

Larva and moth
Figure 1. Golden twin spot moth and looper larva. (photos by S. Hatch and P. Hampson, Bugwood.org)

For the 219 soybean CAPS survey, two moth species that are already problematic elsewhere in the world, but not known to exist in the U.S. were selected.  The Golden Twin Spot moth (Chrysodeixis chalcites), which currently causes yield losses in Africa, Europe, the Middle East and Canada, has a larval stage known as a ‘looper’ which can cause significant damage to soybeans, tomato, cotton, tobacco, beans and potatoes (Fig. 1).  Feeding by the loopers can result in defoliation, and they can also cause foliar damage due to rolling leaves with webbing for nests.  The Silver Y moth (Autographa gamma), which is already a concern in many countries in Asia, Europe and Africa, also has a caterpillar larval state that can cause significant damage to soybeans and many other agronomically important crops, including beets, cabbage, hemp, peppers, sunflower, tomato, potato, wheat, corn and wheat (and many more) (Fig. 2).  These caterpillars also defoliate and harm leaves through rolling and webbing.  Given how potentially damaging an introduction of these pests could be to U.S. agriculture, it’s important that we are vigilant in our efforts to monitor for them and ensure they aren’t in NY.

Silver Y moth and larva
Figure 2. Silver Y moth and caterpillar larva. (photos by P. Mazzei and J. Brambila, Bugwood.org)

In addition to monitoring for these two moth species, we also prioritized a pest that has very high potential to affect soybean yields in NY, and one that has thus far only been confirmed in one field in NYS.  The soybean cyst nematode (SCN) is considered the number one pest of soybeans nationally and globally, causing an estimated 109 million bushels of yield loss in the U.S. in 2017.  Extensive collaborative sampling for this pest from 2014-2017, supported by the NY Corn and Soybean Growers Association and Northern NY Agricultural Development Program, was coordinated by Cornell University and Cornell Cooperative Extension programs.  Over the four years of the SCN survey, numerous fields in 17 counties were sampled, and one field in Cayuga County was identified as positive for SCN in 2016, albeit at very low levels (Fig. 3).  Though it’s promising that SCN wasn’t identified widely across NY, we are fairly confident that it is very likely in many more than just one field in one county.  Given the potential impact this pest could have on NY soybean (and dry bean) production, we decided to include this pest in the 2019 CAPS survey.

Soybean Cyst Nematode
Figure 3. Soybean cyst nematode survey efforts in 17 counties in NY from 2014-2017, with one positive ID in Cayuga County in 2016, and information from the SCN Coalition on why you should test for SCN.

Six collaborators (Jaime Cummings and Ken Wise of NYS IPM, and Mike Stanyard, Mike Hunter, Aaron Gabriel and Kevin Ganoe of CCE) spent part of their typical summer soybean scouting efforts from western, to central, to eastern and northern New York setting up and checking pheromone traps intended to monitor for the Golden Twin Spot moth and Silver Y moth (Fig. 4).  They communicated the importance of these surveys to cooperating farmers who agreed to host these traps in 25 fields across the state.  Any suspicious moths caught in the traps are submitted to the Cornell Insect Diagnostic Clinic for thorough identification.  Thus far, we have not caught any Silver Y or Golden Twin Spot moths.  And that’s good news!  As the growing season winds down, we will collect soil samples from the same 25 fields for SCN testing at the SCN Diagnostics laboratory.

CAPS survey distribution
Figure 4. Distribution of the 2019 soybean CAPS survey.

A funding proposal to continue this work in 2020 has been submitted.  If accepted, it may also be expanded to include a corn CAPS survey for other potentially invasive pests with additional locations in southwest and central NY.  For more information on the national CAPS program, please visit their website.  For additional information on the soybean cyst nematode, please visit the SCN Coalition website, and check out these resources on SCN efforts in NY:  Soybean Cyst Nematode Now Confirmed in NY, Sudden Death Syndrome and Soybean Cyst Nematode in Soybeans, Fall is the Time to Test for Soybean Cyst Nematode.

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Managing Oat Crown Rust to Prevent Yield Loss

Michael R. Fulchera, Gary C. Bergstroma, Mark E. Sorrellsb, and David Benscherb
aPlant Pathology and Plant-Microbe Biology Section and bPlant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY

Crown rust is a continuing threat to oat production in New York, and recent epidemics have cast a spotlight on this disease. To better advise growers on crown rust management, we examined the impact of crown rust on oat grain yields and the disease resistance of available and soon to be available varieties.

The fungal pathogen that causes this disease, Puccinia coronata var. avenae, is widespread in New York and often found on susceptible oat varieties. Characterized by bright-orange, blistering pustules, this disease can be seen from June through August (Figure 1). Once established in a field, disease progresses quickly as the spores of the fungus are dispersed by the wind. The spores are blown to new leaves, different plants and even other fields. Older crown rust lesions develop a black rust spore stage, and these spores can infect the alternate host, common buckthorn, providing early inoculum for oat infections in fields adjacent to infected buckthorn in the following May.

Pustules of crown rust
Figure 1. Orange-brown uredinial pustules (bearing urediniospores) of crown rust on oat leaves.

The pathogen requires living plants to survive so it rarely persists through the winter on oat in New York. However, viable crown rust spores from maturing oat crops in states to our south arrive in New York on wind currents each spring to commence annual epidemics. Some overwintering can occur in New York when the fungus moves back and forth between oat and common buckthorn (Figure 2).

Aecia of crown rust
Figure 2. Yellow-orange aecia (bearing aeciospores) of crown rust on buckthorn leaves in May.

Management of crown rust is best achieved through careful selection of an oat variety. Few options exist to combat the disease after plants are in the field. Some fungicides are labelled for crown rust control in New York, and some growers have realized a return in investment from a timely fungicide spray at or prior to panicle emergence. Crown rust significantly impacts the yield of susceptible varieties and in extreme cases may cause crop failure. Even slight visual symptoms around the soft dough growth stage can translate to yield loss (Figure 3). Rust pathogens are known to evolve quickly to overcome resistance, but based on several years of observation we have identified the varieties that currently are most resistant in New York (Table 1). If you are considering a spring oat planting, choose a variety with proven resistance to current populations of the crown rust fungus in New York.

Bar chart showing effect of crown rust on oat yields
Figure 3. Effect of crown rust infection on oat yields.
Crown rust infection can significantly impact spring oat yields. This plot shows the average predicted yields observed at different disease severities. This data was taken from 360 small research plots spread across western, central and eastern New York in 2015-17. The amount of crown rust damage to flag leaves in each plot was measured during early grain filling. Even when visual disease severity recorded at the soft dough growth stage appears as low as 5%, yield may be limited by crown rust.

Crown rust susceptibility tableLate summer forage plantings are at a higher risk for infection since the spores that cause disease will increase and spread throughout the growing season. When these forage plantings are infected, pathogen overwintering on buckthorn can be increased. This contributes to crop epidemics the following year and may speed the breakdown of oat varietal resistance.

Crown rust will continue to threaten oat yields, but you can reduce the spread of this disease by planting resistant varieties and notifying your local Cornell Cooperative Extension Field Crop Specialist or the Cornell Field Crops Pathology Program if you find the pathogen in your fields.

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What’s Cropping Up? Volume 29 Number 3 – July/August 2019

Organic compared to Conventional Crop Rotations lost $ during the Transition but made more $ in the 2 years after the Transition and in the total 4 Years of the Study

Bill Cox, John Hanchar, Eric Sandsted, and Mark Sorrells

2016 July corn, soybeans, and wheat
The organic corn-soybean-wheat/red clover rotation was the most profitable rotation from 2015 to 2018.

We conducted a 4-year study at the Aurora Research Farm from 2015 to 2018 to compare different sequences of the corn, soybean, and wheat/red clover rotation in conventional and organic cropping systems under recommended and high input management. Unfortunately, we were unable to plant wheat after soybean in the fall of 2016 because green stem in soybean, compounded with very wet conditions in October and early November, delayed soybean harvest until November 9, too late for wheat planting. Consequently, corn followed soybean as well as wheat/red cover in 2017 so we compared two sequences of the corn-soybean-wheat/red clover rotation with a corn-soybean rotation (Table 1). Please refer to previous What’s Cropping Up? articles from 2015 to 2018 for the various inputs for each crop for each year within each cropping system (https://scs.cals.cornell.edu/extension-outreach/whats-cropping-up/). Also, you can refer to Table 2 for a general overview of the management inputs for each crop within cropping systems across years. This article will first discuss the economics of the three crops in Year 3 or 4 of the study. We will then discuss the economics of the three rotations during the 36-month transition period (Year 1 and 2 of the study), the 2-year period after the transition (when the organic premium is in place), and the total 4 years of the study.

Tables 3-6 show the revenue, selected costs, and returns above selected costs for corn in 2017, soybean in 2017, and wheat in 2018. The selected costs differed slightly for each crop across years because of changes in input prices (for example fertilizer and fuel prices change somewhat from year to year). The differences in selected costs between cropping systems for each crop, however, are consistent across years so Tables 3-6 are very representative of selected costs of each crop. On the other hand, revenue and returns for each crop differed significantly across years mostly because of different yields (for example, organic corn averaged ~115 bushels/acre in 2015 but ~185 bushels/acre in 2017), but also because commodity prices varied somewhat across years. So use Tables 3-6 as references in the discussion on selected costs for each crop but not for the revenue and returns for each crop in each year. We didn’t include the 2018 soybean economics data, however, because the differences in revenue and returns between organic and conventional systems were similar as were comparisons between rotations, and  the costs did not vary by more than $6/acre for each treatment.

Organic compared with conventional corn with recommended inputs had ~$15/acre lower selected costs following wheat/red clover (C3 vs. C1 comparison, Table 3) but ~$275/acre higher selected costs following soybean (C3 vs. C7 comparison, Table 3). With high inputs, organic compared with conventional corn had ~$120/acre higher selected costs following wheat/red clover (C4 vs. C2 comparison, Table 4) and ~$365/acre higher selected costs following soybean (C8 vs. C6 comparison, Table 4). As expected, organic compared with conventional corn had lower seed costs because the organic hybrid did not receive a seed treatment and did not have GM traits (Tables 3 and 4). Organic compared with conventional corn had higher fertilizer costs because of the much greater cost for composted poultry manure relative to conventional starter and N fertilizer. The fertilizer and selected costs were much greater for organic corn following soybean (C7 and C8, Tables 3 and 4) compared with following wheat/red clover (C3 and C4) because of the greater N requirement for corn when following soybean. Organic compared with conventional corn also had higher labor, repair and maintenance, and fuel and lubricant costs because of the 4-time use of labor and equipment for mechanical weed control in organic corn (rotary hoe 1x and cultivation 3x) compared with the 1-time use of labor and equipment in conventional corn (herbicide application). Organic compared with conventional corn also had greater fixed costs because of greater wear and tear with the 4-time use of tractors and equipment compared to 1-time use of tractors and equipment for weed control purposes.

Organic compared with conventional corn with recommended inputs had ~$70/acre greater revenue when following wheat/red clover in 2017 (C3 vs C1 comparison, Table 3) and similar revenue when following soybean (C7 vs. C5 comparison, Table 3) in the absence of an organic premium. All prohibited inputs (synthetic fertilizer, GM crops, pesticides, etc.), however, had been applied to the three fields in our study by June of 2014, more than 36 months prior to corn harvest in 2017, so organic corn would have been eligible for the organic premium. We will thus use organic prices for 2017 corn and soybean crops grown under organic management in this study. Organic compared with conventional corn with recommended inputs had ~$830/acre greater revenue following wheat/red clover and ~$685/acre greater revenue when following soybean in the presence of the organic premium (Table 3). Likewise, organic compared with conventional corn with high inputs had ~$990/acre greater revenue when following wheat/red clover (C4 vs. C2 comparison, Table 4) and ~$780/acre greater revenue following soybean (C8 vs. C6 comparison, Table 4). Please keep in mind that organic corn yields averaged ~185 bushels/acre; whereas conventional corn yields averaged ~175 bushels/acre in 2017.  In 2015, however, organic compared with conventional corn had much lower revenue because of ~35% lower yields and the organic premium was not in place (first year of the transition). Likewise, in 2016, organic corn had lower revenue because of 7% lower yields, similar or higher selected costs, and no organic premium (2nd year of the transition). So please use Tables 3 and 4 as representative of selected costs but not of revenue and returns above selected costs.

Organic compared with conventional soybean had ~$20/acre higher selected costs with recommended inputs (S3 vs. S1 comparison, Table 5) but ~$5/acre lower selected costs with high inputs (S4 vs. S2 comparison, Table 5). Organic compared with conventional soybean had lower variable costs because of lower seed and other crop input costs, despite higher labor, repair and maintenance, and fuel and lubricant costs (Table 5). As with organic corn, organic compared with conventional soybean had higher fixed costs because of more wear and tear on the machinery with 5 trips (1x rotary hoeing and 4x cultivations) compared to 1 trip over the field (herbicide application) with recommended inputs or 2 trips over the field (herbicide and fungicide applications) with high inputs .

Organic compared with conventional soybean had ~$55/acre lower revenue with recommended inputs (S3 vs. S1 comparison, Table 5) or with high inputs (S4 vs. S2 comparison, Table 5) in 2017 because of ~8% lower yield in the absence of an organic premium (Table 5). In the presence of an organic premium, organic compared with conventional soybean had ~$370/acre greater revenue with recommended or high inputs. Unlike corn that had inconsistent yield differences between organic and conventional corn across years, organic and conventional soybean yield differences did not vary much (similar yields in 2015 and 2016; ~8% lower in 2017; and ~11% lower in 2018).  Because of the small differences in yield and selected costs, organic and conventional soybean had similar returns above selected costs in 2015 and 2016 and higher returns in 2017 and 2018. Organic soybean with recommended and high inputs had similar returns in 2017 (S4 vs. S3 comparison) as well as in 2015 and 2016 but somewhat higher returns in 2018.

In 2018, organic compared with conventional wheat had ~$160/acre greater selected costs with recommended inputs (W3 vs. W1 comparison, Table 6) and ~$190/acre greater costs with high inputs (W4 vs. W2 comparison, Table 6). Organic compared with conventional wheat had lower seed costs (same variety but no seed-applied pesticide), but much higher fertilizer costs, associated with the use of composted chicken manure, which costs almost 13x the cost of the ammonium nitrate (33-0-0) used on conventional wheat. Organic compared with conventional wheat with recommended inputs in 2018 had ~$205/acre greater revenue because the yields were similar and organic wheat received the organic price premium. Also, organic compared with conventional wheat with high inputs had ~$255/acre greater revenue because of ~7% higher yields and the presence of an organic premium.

Organic compared with conventional wheat with recommended inputs (W3 vs. W1 comparison, Table 6) had ~$45/acre higher return in 2018, despite the ~$160/acre higher selected costs. Obviously the increased revenue, associated with the organic premium, offset the higher selected costs, associated with the use of composted chicken manure. Likewise, organic compared with conventional wheat with high inputs had ~$65/acre higher returns above selected costs (W4 vs. W2 comparison, Table 6). Despite the higher revenue of organic wheat with high vs. recommended inputs, organic wheat with recommended inputs had ~$75/acre higher returns (W3 vs. W4 comparison) because the added revenue from the ~7% yield increase did not offset the higher selected costs, associated mostly with the higher rates of composted manure. Organic compared with conventional wheat, however, had lower returns in 2016 because yields were ~7% lower, selected costs were higher, and the organic premium was not in place (2nd year of transition).

Table 7 shows the costs, revenue, and returns above selected costs of the red clover-corn, corn-soybean, and soybean-wheat/red clover rotations during the transition period, the first 2 years (2015 and 2016) of the study. (A value in Table 7 equals the sum of the 2015 and 2016 values for that treatment). As explained in previous news articles, we planted red clover alone in the early summer of 2015 and plowed it under in the spring of 2016 to see if a green manure crop would provide agronomic and economic benefits to subsequent organic crops in the rotation. The 2-year organic compared with conventional rotations generally had higher selected costs, especially with high input management, mostly because of the very high costs for the composted manure applied to corn and wheat. Revenue was similar as were returns between conventional ($152/acre) and organic ($179/acre) red clover-corn rotations with recommended inputs. Most conventional growers, however, would not plant a green manure crop so a comparison of the organic red clover-corn rotation vs. the conventional corn-soybean rotation with recommended inputs is more appropriate. In this comparison, the organic red clover-corn rotation had ~$455/acre lower returns, similar to the comparison between the conventional vs. organic corn-soybean rotation. The organic compared with the conventional soybean-wheat/red clover rotation with recommended inputs had ~$220/acre lower returns, which proved to be the most economical organic rotation in this study during the transition years. Many conventional growers, however, use high inputs on soybean (200,000 seeds/acre, fungicide/insecticide seed treatment, and foliar fungicide application) and even more so on wheat (high seeding rate, seed treatment, fall herbicide application, split-N application, and foliar fungicide application). A comparison of the organic soybean-wheat/red clover rotation with recommended inputs vs. the conventional soybean-wheat/red clover rotation with high inputs shows only ~$95/acre lower returns during the first 2 years of the transition. All rotations in conventional and organic cropping systems with recommended vs. high inputs had greater returns, except for the conventional corn-soybean rotation, which had similar returns.

During the first 2 years after the transition (2017 and 2018) in this study, selected costs were once again mostly higher in the organic compared with the conventional rotations, especially with high input management (Table 8, a value in the table equals the sum of the 2017 and 2018 values for that treatment). Again, the higher costs for composted manure on organic corn and wheat compared to synthetic fertilizer contributed to the higher costs. The organic compared with the conventional cropping system in all three rotations had much greater revenue because of similar to greater corn and wheat yields or slightly lower soybean yields, coupled with the organic premiums. So despite the mostly higher selected costs for organic compared with the conventional rotations, higher costs did not offset the higher revenue, resulting in much higher returns above selected costs for the organic rotations (Table 8). When averaged across input treatments, organic compared with the conventional cropping system had ~$410/acre higher returns in the red clover-corn-soybean-wheat/red clover rotation, ~$720/acre higher in the corn-soybean rotation, and ~$1200/acre higher in the soybean-wheat/red clover-corn-soybean rotation. When averaged across input treatments in the organic rotation, the organic soybean-wheat/red clover-corn-soybean rotation had ~$435/acre higher returns than the organic corn-soybean rotation and ~$930/acre higher returns than the organic red clover-corn-soybean-wheat/red clover rotation. Similar to the transition period, the soybean-wheat/red clover-corn-soybean rotation was the most economical organic rotation during the first 2 years after the transition.

The organic compared with the conventional cropping system had much higher total selected costs in all 4-year crop rotations, which was more than offset by the much greater revenue in all 4-year crop rotations (Table 9). When averaged across input treatments, the organic compared with the conventional cropping system had ~$270/acre higher returns above selected costs in the red clover-corn-soybean-wheat/red clover rotation, ~$200/acre higher returns in the corn-soybean rotation, and ~$955/acre higher returns in the soybean-wheat/red clover-corn-soybean rotation. When averaged across input treatments in the organic rotation, the organic soybean-wheat/red clover-corn-soybean had ~$470/acre higher returns than the organic corn-soybean rotation and ~$1030/acre higher returns than the organic red clover-corn-soybean-wheat/red clover rotation. Obviously, planting a green manure crop was the least profitable organic rotation to select. Despite the lower returns for organic wheat compared with organic soybean or organic corn, the inclusion of wheat/red clover in the organic rotation was far more profitable than just the corn-soybean rotation over the 4-year period. In contrast, the corn-soybean rotation was most profitable for the conventional cropping system.

In the organic cropping system, recommended input compared with high input management had $412/acre higher returns above selected costs in the red clover-corn-soybean-wheat/red clover rotation and $169/acre higher returns in the corn-soybean and soybean-wheat/red clover-corn-soybean rotation. Consequently, the results clearly suggest that organic cropping systems, regardless of rotation, did not respond to high input management in this study. Many organic growers have been advised to use higher than recommended seeding rates with the goal of improved weed control. In our study, we saw statistically fewer weeds with high input management in corn, soybean and wheat but differences were so small that it had no effect on crop yield in this environment. Based on the returns above selected costs in our study, the use of higher seeding and N rates is not justified in the first 4 years of organic soybean-wheat/red clover-corn-soybean rotation on silt loam soils in central New York.

Conclusions

Field crop producers who transition to organic corn, soybean, and wheat production can generate greater returns above selected costs than conventional field crop producers after 4 years under the environmental conditions of this study, if they can successfully manage the cash-flow challenges during the transition period. To help manage the cash-flow challenges, transitioning growers should not apply prohibited inputs in their last conventional crop after late spring/early summer so the 36-month transition period can be accomplished in two growing seasons. Given the growing conditions during this study and the economic analyses reported here, transitioning growers should not use a green manure crop in the first year of transition but rather plant soybean. Soybean does not require N fertilizer, a major constraint to organic corn and wheat production, so growers should begin their transition in a field where soybean is the intended crop. In addition, soybean with the use of aggressive cultivation is also competitive with weeds, the other major constraint to organic field crop production.

Based on the economic results of this study, field crop producers should include winter wheat as the second crop in the transition after soybean. Organic growers may be able to no-till wheat after soybean harvest, if few winter perennial weeds are observed in the soybean crop. Growers should also frost-seed red clover into standing wheat in early spring, a typical practice for many conventional wheat growers.

Economic analyses of this study suggests that field crop producers, who transition to an organic cropping system, should plant corn in the 3rd year, or the first year when crops are eligible for the organic premium. Organic corn typically has a higher premium when compared with premiums for organic soybean and organic wheat. Corn should follow wheat with interseeded red clover, which provides considerable slow-release N to the subsequent corn crop. In addition, the wheat/red clover crops can disrupt weed cycles, as evidenced by the much lower weed densities in organic corn in the soybean-wheat/red clover-corn-soybean rotation compared with the corn-soybean rotation in 2017. In the 4th year of the study, field crop producers should begin the soybean-wheat/red clover-corn-soybean rotation again by planting soybean.

Based on the economic results of this study, field crop producers should use current recommended inputs for conventional crops and not use elevated seeding rates to improve weed control or use higher N rates to provide more available soil N to corn and wheat. Although the organic compared to the conventional cropping system generated greater returns above selected costs in this study, we recognize that commodity prices, farm size, individual/personal beliefs, and other factors influence a grower’s decision on whether to transition to an organic cropping system. Furthermore, we recognize that the growing conditions and soils were unique to this study so results could differ for different years or locations in New York.

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White Mold of Soybean: What to expect with variable growth stages

Jaime Cummings and Ken Wise, NYS IPM

White mold
Figure 1. White mold infected soybean stem. (Photo by J. Cummings, NYS IPM)

It’s that time of year where we typically consider fungicide applications for white mold protection in our soybeans.  However, this year is a little different.  Soybeans across NY range from V4 to R4 this week, making it a challenging decision regarding whether or when to spray.  As you know, white mold (Sclerotinia stem rot) is our most challenging and undermanaged disease of soybeans across the state (Fig. 1).  It typically rears its ugly head when the rows and canopies close between growth stages R3-R6.  We have no silver bullet for this disease, and therefore rely on an integrated management approach for the best results.

The pathogen produces sclerotia, which are the hard, black survival structures that can easily survive in the soil for at least 10 years, with some reports of up to 20 years.  These long-lived sclerotia, and the wide host-range of this pathogen, make crop rotation as a management strategy difficult, if not impossible.  Resistance to this devastating disease is moderate, at best, in some elite commercial varieties, but none are immune or strongly resistant.  Canopy management is a goal of some growers who struggle with white mold, and efforts include reduced seeding rates and wider rows.  There is plenty of evidence that increased airflow in the crop rows can reduce white mold infection, because the disease is favored by the humid conditions of a dense and closed canopy.  Research on biological control with a product called Contans WG has shown limited or variable efficacy in New York and Michigan, and requires a multi-year commitment for applications for the best results.  However, some NY soybean growers have been successful at reducing white mold incidence and severity in their fields treated with Contans WG, and consider the results well-worth the $35 per acre cost.  Recent research at Cornell by Dr. Sarah Pethybridge (vegetable pathologist) has shown that planting soybeans into roller-crimped rye cover crops can significantly reduce the sporulation of the white mold fungus, resulting in significantly less disease.  Paying attention to the expected weather patterns and forecasting models, such as Sporecaster, are also critical in making white mold management decisions, because this disease can be particularly devastating in times of high precipitation or humidity during temperatures below 85°F.  Though, we have seen fairly severe epidemics in some fields even in hot, dry years.

Nozzle recommendations
Figure 2. Nozzle recommendations for white mold suppression from Michigan State University.

Timely foliar fungicide applications with appropriate nozzles for canopy penetration (Fig. 2), in combination with crop rotation, genetic resistance, canopy management, and biological control remains our best approach for managing white mold in soybean fields.  The main goal for your fungicide applications should be to get them applied BEFORE you have a major outbreak of white mold in your field.  If you have soybeans in a field with a history of the disease, and if the weather conditions are forecasted to be favorable for disease, it’s recommended to get a protective fungicide on between the R1 and R3 growth stages.  Fungicide applications can be a waste of money after R4.  It’s important to note that once you have an epidemic in a field, no amount of fungicide will stop or cure the spread.

Research results table
Figure 3. Research from North Dakota State University shows that combining wider row spacing with timely fungicide applications can decrease white mold disease severity and increase yields.

A number of foliar fungicides are labeled in NY for white mold protection on soybean that are rated ‘Good’ to ‘Very Good’ in the Cornell Guide for Integrated Field Crop Management, based on national replicated field trials.  These include Aproach, Endura, and Omega.  Other fungicides are rated as ‘Fair’, including Topguard, Proline, Domark, and Topsin-M.  It’s important to follow all label recommendations, and note that some products, such as Aproach, recommend two applications when other products may only require a single application.

Field trial results table
Figure 4. Field trial results in Michigan show that both Omega and Propulse fungicides each significantly increase soybean yields, particularly when white mold disease pressure is high.

There have been a lot of soybean white mold fungicide efficacy trials in other states that have similar weather patterns and epidemics to ours, including Michigan, Wisconsin and N. Dakota.   Dr. Michael Wunsch of N. Dakota State University demonstrated that increased row spacing in combination with timely application of Endura fungicide resulted in significantly lower disease incidence and higher yields compared to narrow rows and the non-treated control (Fig. 3).  Mike Staton of Michigan State University demonstrated that a comparison of the fungicides Omega and Propulse showed that they both significantly increased yields compared to the non-treated control, especially in trials with high disease pressure, but that Propulse was a much more cost-effective option (Figs. 4 and 5).  Dr. Damon Smith of University of Wisconsin evaluated the effect of various fungicide combinations and application timings on disease incidence and yield, and found significant improvements in yields from applications of Propulse + Delaro, Proline + Stratego, and a double application of Delaro (Fig. 6).  All registered products evaluated in these trials are labeled for use against white mold of soybeans in NY.

 

Fungicide trials results
Figure 5. White mold fungicide trials in Michigan demonstrate the economics of fungicide applications in fields with high and low disease pressure.
Fugicide efficacy data table
Figure 6. A table from University of Wisconsin outlines fungicide efficacy data on disease suppression and yield for various fungicides products and application timings. (Not all products evaluated in this trial are labeled for use in NY.)

Though we have a number of fungicides labeled for use on white mold in NY, not all field crop dealers carry all products, and pricing may vary by location.  When opting to utilize a fungicide application as part of your integrated management strategy for white mold, keep in mind that there are wide ranges in efficacy and cost among products.  A quick inquiry with only two sources provided prices or price ranges per acre of some of the products you may consider using, as outlined in Table 1 (in alphabetical order, at the highest labeled rates).

Fungicides for white mold in soybeans in NY

Considering the abnormally wide range in growth stages and canopy closure as we experience or approach flowering in our soybean fields, I think we can expect some difficulty in managing white mold in some locations this year.  One of the most perpetuated fallacies I hear is that white mold requires soybean flowers for infection.  Even though this is consistently mentioned in fact sheets and other resources, it is not entirely true.  A soybean plant at any growth stage can succumb to infection by the white mold fungus if the conditions are favorable and if the spores are in the air.  However, soybean flowering usually coincides with canopy closure, and this canopy closure encourages a humid environment within the rows which does enhance disease initiation and progression.  And, shed flower petals do provide a nice food source for germinating spores.  But, again, the flowers are not required for infection.

Although I have seen some nice soybean fields this year that were planted on time, either before or between all of the spring rain events we experienced, much of the soybean planting across the state was delayed this year due to wet conditions.  That means there may be closed canopies with flowering soybeans across the road from fields with much younger or smaller plants.  If the weather favors white mold with moderate temperatures, precipitation and humidity, the disease may initiate in one dense, flowering field and spread among many others.  Or, it may initiate in a field where the plants are stunted with a fairly open canopy, if it’s a field with a history of this disease and favorable weather conditions.  It’s anyone’s guess at when and where a white mold epidemic may happen this year given the variable growth stages and ranges in canopy closure.

Don’t despair, there’s still hope.  I haven’t heard many reports of white mold yet from across the state, which means you still have time to make management decisions.  Get out in your fields to scout, and pay attention to the weather.  Know what growth stages your soybeans are at and how your canopies are looking, and what your neighbors’ beans are doing.  If you have a history of white mold in your fields, and you know that the weather forecast for your area is favorable for the disease, then consider the most cost effective fungicide application to protect your crop.  If you expect dry conditions in a field without a history of white mold, then you can probably skip the fungicide application.  You know your fields best.  But, be aware that the variable growth stages this year may add an unexpected layer of complication to white mold management and timing of fungicide applications.

Thank you to Jeff Miller and Josh Putman of CCE, and Danny DiGiacomandrea of Bayer for assistance with fungicide price ranges.

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Corn and Soybean Weed Control in a Wet Year

Mike Hunter, CCE – North Country Regional Agriculture Team

small common lambsquarters
Small common lambsquarters that emerged before the soybean planted in this field. Photo taken in Jefferson County June 2019

The cool, wet month of May and start of June has created some challenging weed management situations for both corn and soybean.  Unfortunately, delayed planting seasons force growers to focus so much on getting the corn and soybean planted they may not have had the opportunity to make a timely planned preemergence (PRE) herbicide application.

Here is a common situation that we are already encountering this season.  We have a field with corn or soybeans planted and cool conditions have delayed crop emergence but the weeds have already emerged before the PRE herbicide treatment was made.  Do we stick to our original plan and apply a PRE herbicide to this field or do we need to make adjustments to the herbicide program?

If your planned PRE herbicide application has been delayed, it is very important to carefully consider your herbicide choices and make necessary adjustments if any weeds are emerged at the time of application.  With adequate rainfall, PRE herbicides can provide excellent weed control; however, once the weeds are emerged they will generally need some additional product to the tank mix.  The additional product could be another herbicide to add to the tank mix or just an adjuvant such as non-ionic surfactant (NIS), crop oil concentrate (COC) or methylated seed oil (MSO).  There will be many more options in corn than soybeans.

Corn fields not treated with an herbicide prior to crop emergence need to be looked at carefully.  If very small weeds are emerged at the time of the PRE application the answer may be as simple as adding adjuvant to the PRE herbicide.  Consult the herbicide label and follow the adjuvant recommendations based on the products in the tank mix.

If the corn has emerged and the annual grasses are over 1 inch tall and the broadleaf weeds are 2 to 3 inches tall, it may be necessary to add another herbicide to the PRE herbicide.  If the corn is glyphosate tolerant, you may only need to add glyphosate to the preemergence herbicide program.  Using this same scenario with conventional corn, you will likely need to include a postemergence (POST) herbicide to the PRE herbicide.  Examples of POST tank mix herbicides to consider for control of both emerged annual grasses and broadleaf weeds include: Revulin Q, Realm Q, Resolve Q, Capreno, Laudis, Armezon.  The effectiveness of these POST herbicides varies with the control of different annual grasses making proper weed identification critical.  Again, check the herbicide label prior to making any herbicide applications.

If you are using a PRE soybean herbicide it will likely be an Herbicide Group 2 (Pursuit, Python, Firstrate), 3 (Prowl, Treflan, Sonalan), 5 (TriCor, Dimetric, metribuzin), 7 (Lorox, Linex), 14 (Valor, Sharpen) or 15 (Dual, Warrant, Outlook).  Soon after soybeans are planted, there is a narrow window to make certain PRE herbicide applications.  Valor (flumioxazin), Sharpen (saflufenacil), metribuzin and any premixes containing these active ingredients must be applied prior to crop emergence.  Lorox (linuron) is another PRE soybean herbicide that must also be applied prior to crop emergence.  Prowl, Treflan and Sonalan are applied prior to planting soybeans.

Soybean fields not treated with a PRE herbicide after crop emergence where very small weeds have emerged can be more difficult to deal with, especially if a population herbicide resistant tall waterhemp is present.  Recently, Dr. Bryan Brown, NYS Integrated Pest Management Program, conducted tall waterhemp herbicide resistance screening trials at Cornell University.  Using tall waterhemp seeds collected from three different fields in New York, preliminary results indicate that two populations were resistant to glyphosate (i.e. Roundup, Group 9), three populations resistant to atrazine (i.e. Aatrex, Group 5) and two populations resistant to imazethapyr (i.e. Pursuit, Group 2).  Fortunately, none of the tall waterhemp screened were found to be resistant to lactofen (i.e. Cobra, Group 14).

If a population of multiple resistant tall waterhemp is present, our effective herbicide options are limited.  The PRE herbicides that will provide control of multiple resistant (Group 2, 5, 9) tall waterhemp include Dual, Warrant, Outlook (S-metolachlor, acetolchlor, dimethenamid-P), Prowl, Treflan, Sonalan (pendimethalin, trifluralin, ethafluranlin) Valor SX (flumioxazin) and Lorox, Linex (linuron).  If both the soybeans and multiple resistant tall waterhemp have emerged, our effective herbicide options are very limited.  Dual, Warrant and Outlook are the only PRE herbicides listed that can be applied POST; however, these products will not control emerged weeds.  In this situation it would be necessary to include either Reflex or Cobra (Group 14) to the tank mix to provide control of the emerged tall waterhemp.

Soybeans with the herbicide resistant technologies such as Liberty Link (glufosinate tolerant i.e. Liberty), Xtend (dicamba tolerant i.e.Xtendimax, Engenia, FeXapan) and Enlist E3 (2,4-D i.e. Enlist, glufosinate and glyphosate tolerant) provide additional options for POST control of resistant tall waterhemp.

This spring has provided very limited opportunities to plant corn and soybeans due to frequent rainfall and wet field conditions.  This challenging spring has also made it difficult to apply planned PRE herbicides in a timely manner.  It is important to carefully scout your fields before making any herbicide application to make sure the right products are included in the tank mix. And as always, check the herbicide label prior to making any herbicide applications.

 

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