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Weekly Field Crops Pest Report 2009

May 7, 2009            Volume 8 Number 3

1. View from the Field

2. Assess Alfalfa Stands for Brown Root Rot This Spring

3. Prevent Glyphosate-Resistant Lambsquarters

4. Start Scouting for Cereal Leaf Beetle

5. Early Season Corn Diseases!

6. Using NEWA to Determine Growing Degree Days

7. Alfalfa Snout Beetles Begin Spring Emergence

8. Soybean Rust Update

9. Alfalfa Weevil and Growing Degree Days in NYS

10. Clipboard Checklist

11. Mark Your Calendars

12. Contact Information

View from the Field

Ken Wise

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This week I discovered a few clover leaf weevil larvae at the Cornell Research Farm in Valatie. They look similar to alfalfa weevil larvae but are larger with a light brown head and have a white stripe edged with pink that runs the down the back.


Clover leaf weevil             Alfalfa Weevil

For more information about clover leaf weevil please view the Clover Leaf Weevil Fact Sheet from the University of Illinois Extension.

There are many reports of winter kill in alfalfa this spring across New York. Alfalfa winter kill can be caused by a number of factors often involving some type of root disease. Stand counts are a good indication of the health of your alfalfa crop and to help make decisions about the future use of the field. The following chart indicates what an optimum and adequate stand constitutes by years in production. If the number of alfalfa crowns falls below the adequate stand minimum it is considered a poor stand of alfalfa. Take stand counts in 10 locations across the field that are representative of the overall field condition. After collecting the 10 counts, average the number of crowns per square foot.

Crowns per square foot
Harvest Year
Optimum Stand
Adequate Stand
New Spring Seeding
1st hay year
2nd hay year
3rd and older

For more information on this see last week’s weekly pest report for Alfalfa Winter Kill, Root Diseases and Frost Heaving article.

Alfalfa weevil feeding has been observed in the central Finger Lakes region. Although the GDD’s on the particular farm were only 115 GDD, small alfalfa weevil were detected in young leaf buds. The observation comes from a field with light sandy soil that warms up quickly. The field is adjacent to a hedgerow where alfalfa weevil adults likely overwintered. Growers are encouraged to look for signs of weevil feeding while doing early season alfalfa monitoring.

 Brain Aldrich ( CCE Cayuga County) has found cereal leaf beetle eggs in a wheat field. This same field was damaged by cereal leaf beetle last season.

Mike Stanyard (NWNY Dairy, Livestock, & Field Crops Team) also found cereal leaf beetle adults in spring oats.  See article below on cereal leaf beetle management.

Joe Lawrence ( CCE Lewis County) reports alfalfa snout beetle have emerged from the soil and are on the move. For more information on alfalfa snout beetle see the article below.

Assess Alfalfa Stands for Brown Root Rot This Spring

Gary Bergstrom
Cornell University

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If your alfalfa that looked great last October is slow to emerge this spring or if it has suffered apparent ‘winterkill’, brown root rot (BRR) may be one of the main contributing causes.

Brown root rot, caused by the fungus Phoma sclerotioides, is a cold-weather disease affecting the roots and crowns of alfalfa during the dormant period when plants are not actively growing. April through early May is the best time to assess over-wintered alfalfa plants for the symptoms and signs of BRR. It is difficult to diagnose BRR in dead plants, but characteristic lesions can be discerned on the roots and crowns of plants showing slow regrowth of shoots from the crown buds in spring. You will need a good shovel or trowel to dig up plants and a bucket of water to rinse off adhering soil for a closer inspection. A pocket knife is useful for slicing through roots to determine the depth of lesions. BRR lesions vary in appearance, but they are generally light to dark brown, often with a darker border. BRR lesions that girdle the upper tap root or the crown result in winterkill. BRR lesions that girdle the lower tap root or affect just part of the root or crown, can lead to reduced plant vigor and slow emergence of alfalfa in the spring. You can be fairly certain that BRR was a factor in poor winter survival and reduced plant vigor when you see characteristic root symptoms on a high percentage of plants in early spring and there are winterkilled plants interspersed with slowly emerging plants in patches scattered across the field. The severity of brown root rot increases as the plants age and experience more winters.

Absolute confirmation of brown root rot requires a molecular laboratory test that is recently available from the Cornell University Plant Disease Diagnostic Clinic for $40 per composite field sample. The result will be yes/no whether the BRR fungus was present at any level in the overall sample. We suggest you call the clinic at 607-255-7850 prior to submission of samples for diagnosis.

First confirmed within New York in Clinton Co. in 2003, BRR is now known to occur throughout New York, Vermont, New Hampshire and Maine. In New York, high incidence levels of the disease have been observed in alfalfa production fields across western, southern tier, and northern parts of the state. The disease is most severe in regions with harsh winters such as in northern New York and northern New England. Many other stresses to alfalfa plants interact with BRR to cause plant death. Winterkill is not a new problem for New York alfalfa producers. The brown root rot fungus may not be new either though our recognition of it in the Northeast is very recent. The widespread finding of BRR in association with winterkill represents an opportunity to reverse one of the main factors that reduces the productivity and longevity of alfalfa in our region. There is no action that an alfalfa producer can take currently to control BRR, but we hope that ongoing research at Cornell University and elsewhere will change that. With support from the Northern New York Agricultural Development Program we are assessing alfalfa varieties adapted to this region in BRR-infested soils in order to identify varieties that may perform better than others in the presence of the BRR fungus.

Figure 1. Range of typical brown root rot symptoms in alfalfa. Note the light to dark brown lesions and the flaky epidermal tissues within the lesions. Photos by Kent Loeffler, Cornell University.

Prevent Glyphosate-Resistant Lambsquarters

Brian Aldrich
CCE Cayuga County

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Reports continue to come in of poor control of lambsquarters in fields where only glyphosate has been used in glyphosate-resistant soybeans and corn. Prof. Russ Hahn has been collecting seed from these escapes and growing them out in the greenhouse, where glyphosate was applied at various rates and heights. Based on these experiments and field studies, he emphasizes the importance of the height of the lambsquarters when it is sprayed, especially in total post-emergent programs. To better control lambsquarters in a one-pass system in conventionally tilled soybeans, spray glyphosate when lambsquarters is no more than three inches tall. If it is more than three inches tall, increase the rate of glyphosate, or tank-mix with 1/12th oz. Harmony GT XP or 1/12th oz. Unity WDG.

To better control lambsquarters with a two-pass system, apply any of the following preemergents for residual control: 0.89 oz. Python, 1.5 pt. Linex 4L, 1.5 lb. Lorox DF or 2 pt. Prefix. Then apply glyphosate 24-30 days after planting.

For glyphosate-resistant soybeans planted with no-till, if there is significant weed cover prior to planting, a burndown herbicide should be sprayed first.

For better controlling lambsquarters in glyphosate-resistant corn, the introduction of Halex GT in 2007 provided a new option. Halex GT is a mixture of Dual Magnum and Callisto, designed to delay or prevent glyphosate-resistant weeds. This cocktail provides three different modes of action in the way it attacks the physiology of weeds. It’s less likely that any given weed species will be resistant to all three of these ingredients, which helps to prevent the development of resistance.

Remember, Mother Nature loves it when we use the same practices every year, over and over, with no change. Consistency makes it easier for pests to find weaknesses in your defenses and exploit them. That’s why it’s important to change your pest control practices periodically, to throw the enemy off balance; otherwise, slowly but surely, they will find a way through your defensive lines!

Start Scouting for Cereal Leaf Beetle

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It is prime time to begin scouting oats and winter wheat for cereal leaf beetle eggs, larvae, and adults.   Adults of the cereal leaf beetle are 3/16 of an inch long, and their wing covers are a metallic bluish black color, while their legs and front sections are reddish.  Eggs are laid on upper leaf surfaces near the midrib. Eggs are elongate, 1/16 of an inch long, and yellow-brown.  They are laid singly or end to end in short chains of 2 or 3 eggs.  Larvae are about 1/4 inch long, rounded, and usually covered with a slimy black coating.  Only one generation develops per year.

Wheat is now in the stem extension stage of growth, and the flag leaves will emerge within a couple of weeks. Because the flag leaf is so important for grain development and head filling, CLB larvae will be especially damaging if they feed on the flag leaf.  Larvae feed on leaf surfaces between leaf veins, giving the leaves a striped appearance. Heavy infestations give the crop a yellowish white or frosted appearance, but plants can sustain considerable damage before you see any economic losses.  And timing is everything - serious feeding damage in the late head-filling stage does not typically cause economic losses. 

Careful field monitoring for numbers of larvae present is the only reliable way to determine if insecticide application will be cost-effective.  Periodic monitoring should begin now and continue through early heading stages. To monitor a field, carefully inspect 30 stems throughout a field for the presence of eggs and larvae.  The economic threshold is three or more eggs and larvae per stem before the boot stage, or one larva per flag leaf after the boot stage.  If mostly eggs are observed, come back and scout again in about 5 days.

Use of insecticides is usually not recommended because natural enemies, including beneficial parasitic wasps and predators (such as lady beetles) almost always keep populations in check.   It is important to remember that if insecticides are sprayed unnecessarily or excessively, our allies, the natural enemies, will be killed before they can do their job. 

Overall, when sound agronomic practices are used to ensure a healthy crop, impact from cereal leaf beetle will be minimized.


Cereal leaf beetle adult           Cereal leaf beetle larva

Early Season Corn Diseases!

Keith Waldron

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Early season corn seed and seedling diseases can reduce plant populations, thus reducing yields. Some expected yield losses can range from about 5% to 10%. If your average silage harvest is 20 tons/acre, a 10% loss in yield would be 2 tons/acre. The following is how to identify early season seed and seedling diseases:

Seed Decay
Seed decay is caused by a number of soil-inhabiting fungi such as Pythium, Fusarium, Diplodia, Rhizoctonia and Penicillium. The fungi can infect seed before it germinates causing mortality. Seeds infected with decay fungi are discolored and soft. Many times fungal material may grow on the seed. Often when the seed has rotted it may be completely decomposed and cannot be found.

Seedling Blight
Sometimes the seed may germinate and grow but will die as the plant emerges from the soil. Seeding blights are caused by many of the same fungi that cause seed decay. Seedling blight symptoms include discolored seedling coleoptiles and roots. Seedlings may have a wet, rotted appearance before they reach the soil surface. Above ground symptoms of blight may include seedlings that turn yellow, wilt and die.

To manage these diseases make sure a fungicide protectant is on the seed when it is planted. This will limit the disease’s ability to enter the seed or plant.

Using NEWA to Determine Growing Degree Days

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Temperatures have a great effect on insect activity, growth and development. Researchers have extensively studied the biology of some of our key pests in relation to heat accumulation from the environment, and thus we are able to monitor and predict the potential timing of development of damaging stages.  One example of such a pest is the alfalfa weevil.

In past years, we have provided growing degree day accumulation tables for a few locations around New York State in this weekly report.  This year, we encourage our readers to use the NEWA website, where many more locations than we are able to summarize in our brief GDD section can be accessed.

NEWA is NYS IPM’s network for environment and weather awareness.  It is a network of electronic weather instruments associated pest forecast models, and radar weather forecasts.  Weather and pest data is relevant for farmers across commodities, from field crops to fruit to vegetables. Data available include hourly rainfall, temperature, leaf wetness, relative humidity, and soil temperature readings.  All of this information, as well as degree day accumulations are available from almost 50 on-farm locations around NYS, primarily in western NY, the Finger Lakes region, and the Hudson Valley.  Additional information is available from many regional airports.

NEWA homepage

NEWA Growing Degree Day site

NEWA Predictions for Alfalfa Weevil

Be sure to bookmark these locations and check back as often as you need. 

Alfalfa Snout Beetles Begin Spring Emergence

Keith Waldron

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Alfalfa Snout Beetle emergence time....
One indication that spring is here is the sighting of newly emerged alfalfa snout beetle populations. Warmer temperatures should continue to enhance ASB viewing opportunities as adults of this unique species emerge and begin moving to new alfalfa fields.

Alfalfa snout beetles (ASB) are root-feeding weevils found only in nine northern New York counties  (Cayuga, Clinton, Essex, Franklin, Jefferson, Lewis, Oswego, St. Lawrence and Wayne). ASB was also discovered on a number of the thousand islands in the early 1960s. and in Prescott Ontario, Canada in 1986.  The native home of snout beetle is Europe where it can be found from Italy to England and Poland.

ASB adults are mottled gray, humpbacked, 1/2 inch long, do not fly, and are all females. Adult alfalfa snout beetles leave fields void of alfalfa this time of year en mass (by the tens of thousands) in search of new alfalfa fields to lay their eggs. Once they find a suitable location, ASB adults feed on alfalfa foliage and lay eggs that hatch into root feeding larvae. While adult feeding can trim the tops of alfalfa and other hosts, the vast majority of plant death comes from direct root loss caused by ASB larvae feeding.

Alfalfa snout beetle larvae are legless, white, and 1/2 inch long. ASB larvae are found shallow in the soil when very small but move deep in the soil during mid July to late August (18-24 inches). In September the large larvae move back up to the top 8 “ and do most of the tap root severing in September and October.  After development is completed, they then move deep in the soil to overwinter. Larvae move deep in the soil in the fall after feeding (18-24”) and remain there for the next 18 months.  Midway through the summer they pupate but remain deep in the soil until the following spring.

ASB damage in the spring looks similar to winter killed alfalfa with plants failing to “green up”. Areas of dead alfalfa may also indicate presence of brown rot rot.

Alfalfa Snout Beetles in your neighborhood? In addition to alfalfa, other host plants for ASB include: red clover, dock, wild carrot, quackgrass, and white clover. ASB control is best achieved with a three year rotation of alfalfa with a row crop. Non hosts, i.e. good crops to have in rotation to minimize ASB losses include: corn, wheat, oats, soybeans, and potatoes. Insecticides are not recommended to control ASB.

Soybean Rust Update

Gary Bergstrom
Cornell University

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On April 24th, soybean rust was detected on kudzu in Gadsden and Leon counties in Florida. The disease had been detected in both counties on kudzu earlier this year but had not been observed since January.

Soybean rust scouting continues in the Southern U.S. and Mexico. Soybean sentinel plots continue to be established in the Gulf Coast states and kudzu is breaking dormancy throughout the region. In 2009, soybean rust has been found in five states and 17 counties in United States, and in two states and five municipalities in Mexico.

In 2008, soybean rust was found in 16 states representing 392 counties in the United States. Rust was also reported in 14 municipalities (counties) across four states in Mexico.

NYS Soybean Rust Information Center

National Soybean Rust Website

Alfalfa Weevil and Growing Degree Days in NYS

Ken Wise

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Growing degree Days for peak (50%) Occurrence of Alfalfa Weevil growth stage:

Stage or Event
Accumulated growing degree days (48F base temperature)
Eggs hatch
Instar 1
Instar 2
Instar 3
Instar 4
Adult Emergence
(Note: for alfalfa weevil predictions use Base Temp of 48F)

Note: Alfalfa weevil populations may be observed earlier on fields adjacent to overwintering habitat (hedgerows) that have a tendency to warm up more quickly such as those fields planted on light sandy soils, south facing slopes, etc.

CURRENT Accumulated Growing degree days (48F Base)

March 1 -   May 6, 2009

Base 48 F
Base 50 F
Clifton Park
*Indicates missing data

Clipboard Checklist

Keith Waldron

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Emergency contact information ("911", local hospital, Chem. Spill emergency contact, other?) posted in central posting area
*Review EPA Worker Protection Standard training and posting compliance needs
*Walk fields to check tile flow, check and clear drainage outlets.
*Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.
*Watch for winter annual and other early season weed

Finish corn planting by May 15, if soil conditions allow
*Use corn insecticide seed treatment in the planter box, if available, or plant insecticide pre-treated seed
*Monitor for weeds, note presence of "who", "how many" and "where"
*Adjust post emergence weed control actions
*Monitor early emergence, determine corn plant populations, make notes on germination problem

Small Grains:
Monitor winter grains for crop stage, insect and disease problems
*Assess crop for adequate stand and plant vigor

Alfalfa & Hay:
Monitor alfalfa seedings for weeds, insects & diseases.
*Check established alfalfa stands for over wintering injury, frost heaving, alfalfa weevil, weed and disease problems.
*North country counties: Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)
*Timothy stands: check fields for symptoms of cereal rust mite

Check and mend fences as needed.
*Check crop growth
*Review/Plan rotation system
*Early season assessment of field condition and potential noxious weed problems

Check forage allocation and anticipate feed program adjustments as forages are used up from previous year
*Plan where forages should be stored for optimum allocation for feeding
*Keep areas around storage bins and silos clean and mowed

Note any repairs needed for corn planter, seeding equipment, alfalfa harvesting equipment, and tillage implements as they are cleaned and lubricated.
*Service corn planter as needed.
*Calibrate manure spreaders - maintain records on amount spread per field

Emergency responder information on pesticide spills and accidents
CHEMTREC:  800-424-9300
For pesticide information
National Pesticide Information Center: 800-858-7378
To Report Oil and Hazardous Material Spills in New York State
NYS Department of Environmental Conservation Spill Response:
800-457-7362 (in NYS)
518-457-7362 (outside NYS)
Poison Control Centers
Poison Control Centers nationwide: 800-222-1222

If you are unable to reach a Poison Control Center or obtain the information your doctor needs, the office of the NYS Pesticide Coordinator at Cornell University, 607-255-1866, may be able to assist you in obtaining such information.

Mark Your Calendars

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June 4, 2009 -- Small Grains Management Field Day, Musgrave Farm, 1256 Poplar Ridge Rd, Aurora, NY
July 7, 2009 -- Cornell Seed Growers Field Day, Ithaca, NY
July 15, 2009 -- Weed Science Field Day, Thompson Research Farm, Freeville, NY (morning program)
July 15, 2009 -- NYSABA Summer, BBQ, Musgrave Farm, Aurora, NY 12:00 noon
July 15, 2009 -- Weed Science Field Day, Musgrave Farm, Aurora, NY (afternoon program)
Aug. 10-14, 2009 -- Soil Health Training Workshop, Ithaca, NY

Contact Information

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Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316

Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360