What's Cropping Up? Blog

Articles from the bi-monthly Cornell Field Crops newsletter

August 7, 2018
by Cornell Field Crops
Comments Off on What’s Cropping Up? Volume 28, Number 3 – July/August 2018

What’s Cropping Up? Volume 28, Number 3 – July/August 2018

July 23, 2018
by Cornell Field Crops
Comments Off on Impact of Alfalfa Snout Beetle on Dairy Finances in Times of Low Milk Prices

Impact of Alfalfa Snout Beetle on Dairy Finances in Times of Low Milk Prices

Elson Shields, Dept of Entomology – Cornell University, Ithaca, New York

It has been estimated that Alfalfa Snout Beetle costs NNY farmers $445 per cow (or per acre) per year or $44,500 per 100 cows (range $30,000-$60,000), once it has become established on the farm.  The cost estimates are broken down in the following paragraphs.  The Biocontrol Nematode solution to control alfalfa snout beetle currently costs $28 per acre plus application cost.  Research shows a single application provides multiyear control of alfalfa snout beetle. After application, biocontrol nematodes will also reduce the populations of wireworms and corn rootworm when the field is rotated to corn.

Initially, when alfalfa snout beetle move onto a farm, its presence is unnoticed for several years.  The farmer begins to notice a more rapid loss of alfalfa stands, and shortening of alfalfa stand life, requiring more frequent replanting of alfalfa fields or farming them as grass fields.  As ASB moves into additional fields, the farmer gradually begins to purchase more off-farm protein to offset the losses of high quality forages from alfalfa snout beetle.  It is often a decade after the initial infestation of alfalfa snout beetle that the farmer realizes the farm is no longer as profitable as it once was and the causes of this lost profitability is often misidentified.

The true cost of alfalfa snout beetle moving onto the farm can be separated into three distinct areas.  1)  The cost of alfalfa stand loss (stand establishment and loss of yield, 2)  The cost of the off-farm protein to replace the lost forage quality and 3)  Resulting impact on the farm CAFO plan from the increased phosphorus brought on the farm with the increased purchases of protein like soybean meal.  The following cost estimates do not include the impact on the farm CAFO plan.

1)  Cost of Stand Loss from Alfalfa Snout Beetle damage:

With the assistance of Ev Thomas, Oak Point Agronomics, Ltd, Mike Hunter, NNY CCE and Tom Kilcer, Advanced Ag Systems LLC, it was estimated that alfalfa stand loss from alfalfa snout beetle cost the farmer between $200-$400 an acre per year in a three cut 4 yr rotation system and $200-$500 per acre per year in a 4 cut – 3 yr rotation system.  The cost figure is a combination of establishment costs, loss of yield and fixed land costs.  The variation in cost is dependent on the speed of stand elimination by alfalfa snout beetle.  If stand is eliminated in a single year, the higher cost is appropriate and if the stand is eliminated over 2-3 years, the lower cost is appropriate.  A middle of the road figure would be $325 per acre per year.  Using the rule of thumb that one acre of forage feeds a cow for a year, stand losses from alfalfa snout beetle equals $325 per cow per year.

2) Increased Feeding Costs due to loss of high quality forage from Alfalfa Snout Beetle:

With the assistance of Ev Thomas, Oak Point Agronomics and Michael Miller, W.H. Miner Institute, using a diet of 30% forage & 70% corn, the cost of soybean meal to replace the lost alfalfa was estimated to be:

Situation 1:  Clear Seeded Alfalfa is lost and replaced to High Quality Grass (15% CP)

Extra Soy Cost in Diet = $9.30 per cow per month ($111.60 per cow per year).

100 cows = $930 per month or $11,160 per year.

Situation 2:  50% alfalfa and the alfalfa is replaced with High Quality Grass (15% CP)

Extra Soy Cost in Diet = $4.70 per cow per month ($56.40 per cow per year).

100 cows = $470 per month or $5,640 per year.

Situation 3:  Clear Seeded Alfalfa is lost and replaced to Ave Quality Grass (11% CP)

Extra Soy Cost in Diet = $16.80 per cow per month ($201 per cow per year).

100 cows = $2,010 per month or $20,100 per year.

Situation 4:  50% alfalfa and the alfalfa is replaced with Ave Quality Grass (11% CP)

Extra Soy Cost in Diet = $8.40 per cow per month ($100.80 per cow per year).

100 cows = $840 per month or $10,080 per year.

A middle of the road figure would be $10 per cow per month ($120 per cow per year) and 100 cows = $1,000 per cow per month ($12,000 per year) (range $5,640 – $20,100 per 100 cows per year).

This brings the cost of alfalfa snout beetle on the farm to $445 per cow per year (every year) and that cost is broken down in the following manner (Not accounting for the impact on the CAFO plan for the dairy).

Stand and Yield Loss:             $325 per acre (per cow) per year (range $200 – $500)

Extra Soy costs:                      $120 per cow per year (range $56.40 – $201)

Total:                                       $445 per cow per year (every year).

(100 cows  = $44,500, range $30,000 – $60,000)

Control of Alfalfa Snout Beetle with Biocontrol Nematodes:

Research has shown a single application of biocontrol nematodes in a field at a current cost of $28 per acre plus application costs will control alfalfa snout beetle for multiple years.  When the field is rotated into corn, research has also shown impact on wireworms and corn rootworm.  After 4 years of corn, research has shown that the biocontrol nematodes remain in the field at sufficient populations to provide continual control of alfalfa snout beetle.  Even with terrible milk prices a farmer cannot afford not to apply biocontrol nematodes.  (savings = $445 – $28 = $417 per acre (cow) or $41,700 per 100 cows).

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March 9, 2018
by Cornell Field Crops
Comments Off on Western Bean Cutworm and Mycotoxin Screening – 2017 New York and Vermont Corn Silage Hybrid Trials

Western Bean Cutworm and Mycotoxin Screening – 2017 New York and Vermont Corn Silage Hybrid Trials

Joe Lawrence, Gary Bergstrom, Jaime Cummings, Elson Shields, Ken Wise, Mike Hunter

Mold and mycotoxin development in corn ears and the resulting corn silage continues to be a major concern for dairy producers. Mycotoxins can result in a range of problems for livestock throughout the year as they are ingested with the feed. The presence of mold does not always have a strong correlation to mycotoxin development but it does present the chance for incidence to occur.

A number of factors influence the prevalence of molds from year to year. Conducive weather conditions for mold and mycotoxin development are outside the control of management options. But hybrid characteristics and physical damage to the ears can be managed through the selection of hybrids and pest resistance traits in the hybrids.

The presence of Western Bean Cutworm (WBC) in NY corn fields continues to expand as shown in the WBC Pheromone Trap Network coordinated by the NYS IPM program, though the insect’s apparent population varies significantly across the state (Figure 1).

Where WBC populations are high, the corresponding ear damage from WBC feeding can leave wounded corn ears more susceptible to pathogen development, but a clear relationship between ear damage and mycotoxin development has not been documented. A number of mold species may develop on corn ears and a relatively few of these produce mycotoxins. Principal concern in New York is with the mycotoxins deoxynivalenol (DON or vomitoxin) and zearalenone, both produced by the fungus Fusarium graminearum.

While WBC damage to corn ears can be significant and may have detrimental effects on corn grain yield and quality, the economic impact on corn silage is less understood. For corn silage growers, understanding whether or not this pest significantly impacts the yield or quality of the forage is critical to their decision making for managing this pest.

Since the Cry1F protein, which has most commonly been utilized for protection against numerous corn insect pests, has been found to be ineffective against WBC, producers are left with limited management options. Currently the Vip3A trait in select corn hybrids in combination with a scout and spray program is the best option for WBC management in areas where the pest is prevalent.

The Commercial Corn Silage Testing program conducted by Cornell University in collaboration with the University of Vermont and the Northeast dairy industry offers a good opportunity to evaluate numerous hybrids for ear damage from WBC and mycotoxins. This was done in 2017 with support from both the New York Corn Growers Association and the Northern New York Agricultural Development Program.

In 2017, 49 hybrids were selected and planted in replicated plots at two locations in NY (Aurora and Madrid). Each plot was scouted prior to harvest for WBC feeding damage to the ears. Composite samples, of whole plant silage, for each hybrid were taken at harvest and submitted to the Dairy One forage laboratory for a mycotoxin screening package which included aflatoxins B1, B2, G1, G2, vomitoxin, 3-acetyl DON, 15-acetyl DON, zearalenone, and T2 toxin.

The results of the WBC and mycotoxin screening project revealed large differences in the number of hybrids damaged by WBC, but surprisingly few hybrids tested positive for measurable mycotoxins (Table 1).

The most prevalent species of mycotoxin-producing mold found in the screening was Fusarium graminearum which can also infect corn ears through the silk channels at the time of pollination during favorable weather conditions and result in contamination of the grain and silage with the mycotoxins DON, 3-ADON, 15-ADON, or zearalenone. A review of the 2017 weather data at both trial sites showed wet conditions conducive to this type of infection. As expected for New York, no aflatoxins were detected.

While there are numerous ways in which molds can establish themselves in forages, this study reflects a common challenge researchers face while attempting to document the conditions where mycotoxin development is likely. Recognizing that results are specific to the growing season experienced in 2017, which was conducive for silk channel infections. A different relationship between WBC damage and mycotoxin development may be found during a growing season less conducive to silk channel infections. These results from one year of data do not provide strong evidence that WBC damage is a significant concern for corn silage growers who are worried about mycotoxins in their silage. Multiyear studies, including years of varying weather conditions, are required for further evaluating these risks and providing recommendations. It is also important to note that these results do not reflect what may occur in corn harvested for grain as the time between silage harvest and grain harvest offers additional opportunities for infection and growth.

Additionally, there was no correlation between crop yield or starch content with WBC damage in this study. Growers should continue to scout for this pest and weigh the cost of control with the potential for damage.

An article addressing integrated pest management (IPM) practices for WBC has been generated by the NYS IPM team.

Integrated Pest Management for Western Bean Cutworm (Richia albicosta), https://blogs.cornell.edu/ipmwpr/

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February 9, 2018
by Cornell Field Crops
Comments Off on What’s Cropping Up? Volume 28, Number 1 – January/February 2018

What’s Cropping Up? Volume 28, Number 1 – January/February 2018


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February 1, 2018
by Cornell Field Crops
Comments Off on Cover Crop Induced Insect Problems

Cover Crop Induced Insect Problems

Elson Shields, Entomology Department, Cornell University

The increased adoption of cover crops as a soil conservation and soil health building strategy is not without increased risk from insect pest problems.  Increased insect pest risk can be managed with a combination of timely killing of the cover crop, pest scouting, and additional timely application of insecticide.

The best-case scenario for the management of the cover crop to reduce insect risk is to kill the cover crop far enough in advance that the cover crop is completely dead prior to the planting of the crop.  Foliar feeding insects often can survive on the dying cover crop, and if the new crop emerges before the cover crop is completely dead, the foliage feeding insects simply move from the dying cover crop onto the newly emerged and tender crop plants.  This is termed a green bridge.

The worst-case scenario for insect risk is to plant into a green cover crop which has been rolled prior to planting and then sprayed with an herbicide to kill it after the crop has been planted.  This provides an excellent green bridge for the insects, like black cutworm larvae and armyworm larvae, to move directly onto the newly emerging crop.

Cover Crop Bridging Insects:

Black cutworm:  Black cutworm is a long-ranged migrant which overwinters in the southern US.  Moths typically arrive in NY during mid-April to early-May on the early weather systems.  Moths are attracted to grassy areas, grassy cover crops, grass waterways, and fields with grassy weed problems.  Eggs are laid on these plants and larvae begin feeding on these plants.  In the situations where producers kill the cover crops or grassy weed areas with herbicide or tillage, the black cutworm larvae continue to feed on the dying plants for 1-2 weeks.  When corn seedlings start emerging, the existing larvae then move from the dying plants onto the growing corn.  Since black cutworm larvae do not start their cutting behavior until mid-size (L-4), the early larval development on the grassy weeds is a critical association with the economic association of black cutworm to seedling corn.  In the situations where eggs are laid on emerging corn, corn development to V6, a stage where black cutworm has difficulty cutting occurs before the black cutworm develops to the larval stage where they begin cutting (L4).

Since black cutworm larval development on existing plants in the field prior to the planting and emergence of the corn is a critical component in the development of economic infestations, the management of the green plants prior to corn planting is important.  Elimination of the green bridge between the cover crop and/or grassy weed cover at least 2 weeks before the emergence of corn seedling dramatically reduces the risk of a black cutworm infestation in NY corn fields.  If the separation between the killing of the cover crop/grassy weeds and the emergence of the corn crop cannot be at least 14 days, the corn seedlings need to be scouted for the presence of foliar feeding, early cutting and the presence of larvae.  To the trained eye, pre-cutting foliar feeding is very obvious and easily detected.

Armyworm:  Armyworm is a long-ranged migrant similar to black cutworm, but often arrives 15-30 days later in NY.  It overwinters in the southern US, and the moths emerging in April in the south use the weather systems to move long distances.  When the moths arrive, they are attracted to grass hay fields or grassy cover crops.  If the eggs are laid in the hay field, larvae will feed on the grass and only move when the field has been stripped, thus the name armyworm.  Neighboring corn fields are then attacked by the larger marching larvae.  When eggs are laid in a grassy cover crop, the larvae will feed on the cover crop until it is stripped before moving.  If corn is emerging in the cover crop, they will simply move onto the young corn plants.  Armyworm larvae are totally foliage feeders and do not cut plants like black cutworm.  With timely scouting, this insect is easily controlled with an application of foliar insecticide.  Usually, the infestation is missed until the field is stripped and the larger larvae are moving into a neighboring field.

Seed corn maggot:  Seed corn maggot (SCM) adults (flies) are attracted to decomposing organic material.  This organic matter can range from animal manures to decomposing plant material/killed cover crop.  Fresh decomposing organic matter is more attractive to the flies for egg deposition than composted organic matter; although, SCM will also lay eggs in composted organic matter.  Adult flies are present for egg laying from early May until late September.  The highest risk fields for SCM problems would be a green manure crop covered with a thick layer of animal manure prior to planting the crop.  High manure application rates without thorough incorporation before planting of large seed crops is a high SCM risk field.  Damage from SCM is plant stand reduction, and without insecticide protection, plant stands can be reduced 30%-80%.  The primary reason for insecticide treatment (Poncho, Cruiser, etc) on large seed crops (corn, soybeans) is protection against SCM-related plant stand loss.  Under extremely heavy SCM pressure, the insecticide seed treatment can be overwhelmed, resulting in corn/soybean stand losses.

To reduce risk from SCM, cover crops should be killed and allowed to turn brown before planting the season’s crop.  In addition, applications of manure should be subsurface rather than surface applied.

Wireworms:  Adult wireworms (click beetles) are attracted to small grains, grass fields, run-out alfalfa fields which are mostly grass, and grass-based cover crops.  Adult beetles search out these hosts during the growing season (June-August) and lay eggs.  The larvae (wireworms) hatch and feed on a wide array of roots for multiple years.  In cropping sequences where grassy/small grain/cover crops are present in the field during the June-August period, wireworms feeding on new seedlings and root crops can become an economic problem. While corn is technically a grass, wireworms do not find corn fields attractive for egg laying.  However, small grains are very attractive.  Generally, spring planted grains are more attractive than fall planted grains which mature in early summer.  In conventional production systems, the insecticide seed treatment generally is effective at reducing the impact of wireworm feeding.  However, in the organic production system, there are no effective rescue treatments for wireworm infestations/feeding damage.  If grassy cover crops are the only grass in the cropping sequence, timely crop termination before June will reduce the attractiveness to wireworms for egg laying.

White grubs:   In NYS, there are two different groups of white grubs which can be problematic.  The first group is the native white grubs which have multi-year life cycles and the second group is the invasive annual white grubs (Japanese Beetle, European Chafer).  Adults from both groups are attracted to grassy habitats to lay their eggs during mid-June to mid-July.  Eggs hatch during August, and the larvae begin to feed on grass roots.  In the case of the invasive annual white grubs, the larvae grow quickly and achieve more than 50% of development before winter.  In the spring, the larvae resume development and are quite large when the grassy field is rotated to corn or soybeans and the new plants are quite small.  Plant death is caused by these large larvae feeding on plant roots faster than the plant can generate roots.  Larvae become adults in June and the cycle repeats.  In the case of the native multiyear white grubs, the life cycle is similar but larval development requires 2-4 years depending on the species.  Subsequent crops following the grassy/cover crop/small grain field are then impacted differently.  With annual white grubs, the damage to the subsequent crop is confined to the following year only.  In the case of native white grubs, subsequent crops could be impacted up to 4 years with declining damage levels each year.

The following two different cropping scenarios seem to place subsequent crops at higher risk.  The most common case is the alfalfa field which has become mostly grass or a grass hay field which is then rotated into a large seed crop like corn or soybeans.  The second scenario is the field which has been planted to a grass-based cover crop and not killed during the June-July egg laying period.  In most cases, the insecticide seed coating on all corn and some soybean seeds reduce the impact of white grubs on subsequent crops.  High white grub populations can overwhelm the insecticide, however.

Slugs:  Increasing the organic soil cover with either the use of cover crops or last year’s crop waste increases the slug problem.  In cool wet springs, which slow plant emergence and growth, damage from slug feeding can be severe.  There is a little anecdotal evidence to suggest the presence of green cover reduces the slug damage because of the surplus of green tissue.  In these cases, slugs miss the newly emerging plants and feed on the green cover crop.

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January 30, 2018
by Cornell Field Crops
Comments Off on Corn Rootworm Management Strategies for 2018

Corn Rootworm Management Strategies for 2018

Elson Shields, Entomology Department, Cornell University

The excessive wet soil conditions during the 2017 corn rootworm (CRW) hatching period during late May – early June caused a major reduction in corn rootworm adult populations during the 2017 growing season.  Adult surveys in most fields during early August showed a scarcity of adult beetles during the egg-laying period.  As a result, most fields in NY will have a reduced risk for CRW damage during the 2018 growing season.  In these lower risk fields, CRW management costs can be reduced by growing non-Bt-CRW corn and using either a reduced rate of soil insecticide or the 1250 rate of seed treatment.  First year corn is never at risk from CRW and therefore Bt-CRW corn, a soil insecticide or the 1250 rate of seed treatment is an unnecessary expense.  This includes any application of Capture in the pop up fertilizer.    Well drained fields which did not experience the typical periods of water logged soils during late May – early June 2017 will be at higher risk from CRW injury in 2018 and should be managed accordingly.  These higher risk fields may benefit from planting Bt-CRW corn varieties.  In “normal” years, the risk of economic damage from CRW is 0% – 1st year corn, 25%-35% – 2nd year corn, 50%-70% – 3rd year corn and 80%-100% for 4th year and longer continuous corn.

Status of Bt-CRW resistance in the US:

CRW Bt resistance continues to build across the corn growing regions of the US with multiple localized resistant populations identified for each of the Bt-CRW traits.  Cross resistance has been identified within the Cry3 family (Cry3Bb1-Yieldgard Rootworm, eCry3.1Ab-Duracade, mCry3A-Agrisure RW) and if one of the Cry3 traits are failing in your field, the planting of another toxin within the Cry3 family may lead to disappointing CRW management results.  Resistance has also been reported in several states to Cry 34Ab1/Cry35Ab1. There has been no reported cross resistance between the Cry3 family of toxins and Cry34Ab1/Cry35Ab1 toxin combination.

The rootworm Bt-toxin pyramids consist of two different Bt-RW toxins in the same plant.  Some seed companies have included two different toxins from the Cry3 family where cross resistance has been reported where other seed companies utilize the pyramid mix of a toxin from the Cry3 family and Cry34Ab1/Cry35Ab1 where no cross resistance has been reported.  If control failures have been reported in your fields/region to any one of the Cry3 family of toxins, planting a pyramid composed of two different Cry3 toxins is not recommended.  Instead, it is a better CRW resistance choice to plant a pyramid consisting of a Cry3 toxin with the Cry34Ab1/Cry35Ab1 toxin.

A very handy resource to identify the Bt traits in your corn varieties is the annually updated Bt trait table.  The 2018 Handy Bt Trait Table for US Corn Production is made available by Dr. Chris Difonzo, MSU, Dr. Pat Porter, Texas A&M and Dr. Kelley Tilmon, OSU can be found at the following URL:


As Bt –CRW traits are failing to resistance by corn rootworm, the promise of the next effective trait is ever appealing.  The development of the RNAi technology against CRW has been touted as the next effective plant incorporated toxin with a very slim chance of resistance development by CRW.  However, it only took about 20 million individuals from a single Illinois continuous corn field and a few generations to generate an RNAi resistant laboratory population. In addition, field results with RNAi containing corn varieties suffer a noticeable amount of root feeding damage before the slow-killing toxin kills the insect larvae.  As a result, the new RNAi technology will not be the “silver bullet” everybody has hoped for.  Stewardship of the Bt technology has become increasingly important in areas where Bt resistance has not been reported because the next technology needs effective Bt toxins to help it out.

Bt Trait Stewardship Suggestions:

A few simple management adjustments can go a long way in preserving the efficacy of the Bt-CRW traits in NY.

  • Long-term corn fields need to be rotated to a non-corn crop on a regular basis.  Continuous corn matched with a long-term use of same Bt-CRW trait promotes the development of a resistant population.
  • Rotate toxins between the Cry3 family and Cry34Ab1/Cry35Ab1 toxins. There is no recorded cross resistance between these two groups of toxins.
  • Use the Bt-CRW technology only in fields of 3rd and longer continuous corn fields. Rotate the toxin groups and rotate the long-term corn to at least 1 year away from corn to break the CRW cycle.
  • Plant some fields to non-Bt-CRW varieties and use either a granular soil insecticide or the 1250 rate of seed treatment. Liquid insecticides in the popup fertilizer are not effective and not recommended.
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