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Weekly Field Crops Pest Report 2008

May 8, 2008                 Volume 7 Number 4

1. View from the Field

2. Weather Outlook May 8

3. Early Season Foliar Diseases of Alfalfa

4. Start Scouting for Cereal Leaf Beetle

5. Quantifying Row Crop Plant Populations

6. Fungicides for Management of Foliar Diseases of Wheat

7. Alfalfa Weevil Growing Degree Days Update

8. Soybean Rust Status

9. Clipboard Checklist

10. Up-Coming Events

11. Contact Information

View from the Field

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Eastern NYS-Ken Wise

At the Cornell Research Farm in Valatie this week I saw a few alfalfa weevil adults. There were not alfalfa weevil eggs to be found injected into the stems of alfalfa or henbit. I did see a substantial amount of clover root curculio adults.  This is a small beetle that lives in alfalfa and clover fields. Adults nip at the leaves and their below the ground feeding grub-like larvae feed on root nodules and damage alfalfa roots, which can predispose plants to infection by root diseases.

Clover Root Curculio Adult

This prompted me to look at some of the tap roots of alfalfa and clover at the farm. I did find substantial root and crown rot in some of the fields. Root and crown rot can infect an alfalfa or clover plant in many different pathways. As suggested above, root injury by insect feeding creates openings that allow pathogens to enter. Most of these diseases are different kinds of fungi like Fusarium spp., Phoma, Pythium, and Rhizoctonia, as well as a few kinds of bacteria that can enter the root and cause root rot and/or crown rots. Seen in the photos below are the typical signs of root and crown rot in alfalfa and clover.

Root Openings

Root and Crown Rot

Poor soil drainage and wet spots in the field can also affect alfalfa/clover growth and development. The same diseases listed above can also infect the plant if the soil is overly water logged or wet.

Western NYS

Dean Sprague reports that 40 to 50 deer were feeding on a wheat field earlier in the spring. The farmer was concerned to know if the grazing would reduce the yield of wheat. If the deer feeding occurs before wheat stem elongation the grazing should not cause a yield loss. If stem elongation has started deer grazing could affect the yield.

Dr. Gary Bergstrom reports that wheat streak spindle mosaic virus symptoms (WSSMV) have diminished due to the warmer temperatures that occurred in Western NYS a couple of weeks ago. Wheat soil borne mosaic virus (WSBMV) was very prominent in fields that had the disease. Gary states that most of the wheat varieties we grow in NYS are susceptible to WSBMV.

Janice Degni reports there were substantial amounts of chickweed and purple deadnettle growing in the under-story of alfalfa fields. Dr. Russ Hahn suggests that if there are a lot of these weeds in a new seeding it would be a good idea to control them. In an established stand of alfalfa it may or may-not be a good idea to control them depending on the economics.

Weather Outlook

Kathy Vreeland
NOAA Northeast Climate Center, Cornell

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 An approaching warm front last Friday was followed by a cold front that quickly exited New York on Sunday. Rainfall during this period generally ranged from 0.25 to 0.75 inches. After a few rain-free days, mainly light showers traversed the state late Wednesday into Wednesday night. Temperatures for the week ending May 7th averaged about 3 degrees below normal with the greatest departures in the central lakes, eastern plateau and northern plateau.

There were 25-50 GDD days during the last week which put the seasonal total in the 50 to 200 range across the state. This was greater than the same time period last year. The state averaged 3 to 14 GDD above normal with the greatest departures in the north, central and western parts of the state.


Today will dry out from northwest to southeast as high pressure builds over New York. Temperatures will be near or slightly below normal.  Low pressure over the Tennessee Valley will lift north and east, bringing the chance of rain to the southern and eastern parts of the state on Friday. Chance of rain is greater in southern and central NY and less to the north. Up to 1 inch of rain possible in areas of heaviest rainfall across NY with higher amounts (up to 3 inches) possible across PA and NJ. Temperatures will be below normal to the south and near normal to the north. A weak ridge is expected to build over the region on Saturday before the next system comes into play later on Sunday. Discrepancies in model, but expect rain, possibly heavy, later on Sunday into Monday with cooler temperatures.

Longer outlook

Temps below normal and above normal precipitation.

Early Season Foliar Diseases of Alfalfa

Ken Wise

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Spring Black Stem: is favored by cool and moist weather in early spring. Symptoms appear as irregularly shaped brown to black spots that can merge to form a larger blotch. This disease can infect the petiole, form elongated blackened areas on the stems, and may be a contributor to a crown rot. Spring Black Stem

Common Leaf Spot: proliferates when the weather is cool and wet. This disease first develops on the lower leaves near the soil surface and then progresses upward through the canopy. Common leaf spot appears as small, circular, dark brown to black spots, about 1/16 inch in diameter. When observed through a hand lens, tiny raised, light brown disk-shaped fungal fruiting bodies are visible in the center of mature lesions. See photo at: Common Leaf Spot

Leptosphaerulina Leaf Spot (aka “Lepto”): is also favored by cool and moist weather in early spring and late summer to early fall. The lesions usually start as small black spots and enlarge to oval or round “eyespots” 1/16 to 1/8 inch across. As lesions develop they become light brown or tan with dark brown borders; often surrounded by a chlorotic (yellow) area. This disease primarily attacks young leaflets but may also attack petioles and other plant parts. See photo at: Leptosphaerulina Leaf Spot

Downy Mildew: causes leaves to become blotched or chlorotic (light green or yellow). Many times young leaflets can become distorted. Often a dark purplish-gray fungal mat covers the underside of the leaves. This disease is common early in the spring. See photo: Downy Mildew

While alfalfa leaf spots may be easily found in most stands the real impacts for this harvest would be if 30% or more of the leaves on plants were shed as the result of infection.

For more information view our on-line management guide: Alfalfa Diseases (Leaf Spots) Management

Start Scouting for Cereal Leaf Beetle

Julie Dennis

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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

Quantifying Row Crop Plant Populations

Keith Waldron

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Weather outlook for the next week looks like temps below normal and above normal precipitation. These conditions may slow seed germination or seedling emergence. Slower emergence can favor some emergence problems such as seedling blights and seed corn maggot. Checking emergence of corn populations is critical to detect stand problems early.

Seeing gaps within rows? Check for proper soil pH? N-P-K matched to soil test recommendation? Nice seedbed preparation? Timely planting? Plant Population? - Check?

How many corn seeds did you plant and what did you get?
It's important to evaluate stands early to determine if the optimal plant population has been achieved. A good stand or a replant situation? One EZ method for determining plant populations is to count the number of plants per 1 / 1,000th of an acre. Determine the length of row you'll need to count plants in by referring to the row width table below. Then determine the average of three sets of emerged plant counts found at several locations throughout the field to get the average number of plants per acre. Finally, determine the average number of plants found in the length of row sampled and multiply by 1,000 to get the average plant population.

Locate wheel tracks and make observations for each row planted. Check at least three areas within the field for consistency and to determine if all planter boxes were operating well.

Row Width (in)                 Length of Row per 1/1,000 of an acre

                                          Feet                                   Inches

7                                        74                                      8

15                                      34                                      10

28                                      18                                      8

30                                      17                                      5

32                                      16                                      4

36                                      14                                      6

A 10% reduction in number of plants observed vs number of seeds dropped is not uncommon. Large deviations from what was expected can signal a variety of potential problems. If your plant population counts are not up to snuff, sometimes waiting a few days and re-doing the estimate can make a difference if there is uneven germination from cool temps or variations in seeding depth. Other potential problems can be related to poor seed germination, planter calibration, performance and planting associated problems, poor soil conditions, seed rots or seedling diseases, seed corn maggot, wireworm, white grubs, birds, mice, and other factors.

Fungicides for Management of Foliar Diseases of Wheat

Julie Dennis

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Wheat is now in the stem extension stage of growth, and it is time to be scouting for fungal diseases including powdery mildew and the leaf blotch diseases.  See recent issues of this Pest Report for Ken’s photos and discussion of the leaf blotch diseases, including Stagonospora nodorum blotch, which may cause small to moderate yield losses almost every year.

Gary reminds us that yield losses from fungal diseases are greatest when disease develops on the two upper leaves during flag (top) leaf emergence (late May) through kernel dough (late June) stages.  Protecting the flag leaf is a key to preventing losses.

Gary reports this week that powdery mildew is prevalent on susceptible varieties of wheat in several locations in western NY. Spores of leaf rust arrive on air currents from southern regions of the US , and are not usually present in NY until June or July.

Viral diseases of wheat, particularly wheat soil borne mosaic virus in certain areas of the Finger Lakes Region, are present now, but bear in mind that foliar fungicides have no effect on viral diseases (also including wheat spindle streak mosaic and barley yellow dwarf).

With the high grain prices, many farmers are more likely to be considering the use of foliar fungicides on their wheat crop than they have in recent years.  Gary Bergstrom, Cornell Extension Plant Pathologist, recently brought us up to date on the current information on disease management with fungicides. For a full update from Gary , including fungicide recommendations, please visit: Wheat Fungicide Options for 2008

Alfalfa Weevil Degree Days Update

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*

Eggs hatch             280

Instar 1             315

Instar 2             395

Instar 3             470

Instar 4             550

Cocooning              600

Pupa                            725

Adult Emergence          815

* 48F base temperature

CURRENT Accumulated Growing degree days (48F Base)

March 1 -  May 7, 2008

                                    48F                 50F

Batavia:                        268                  226
Chazy:                          227                  194

Clifton Park:                 394                  345
Geneva:                        257                  213
Ithaca:                          179                  148*

Prattsburg:                    218                  182

*Missing Data

Soybean Rust Status

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Soybean rust was confirmed by the USDA on a new host, Coral bean or Cherokee Bean (Erythrina herbacea) on samples collected in Marion County, Florida.

Rust continues to be found in the southern U.S. Active disease is still being reported on kudzu in six counties in Florida and one county in Texas. Efforts continue in the Gulf Coast Region to establish soybean rust sentinel plots.

Coordination of soybean rust sentinel plots in New York State is currently underway. Many of last year’s cooperators will be volunteering their time again to establish and scout these plots. Please visit us again for future updates.(Updated May 5, 2008 )

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

*Maintain crop records by field, including variety, planting date, pesticides used, nutrient inputs including manure, etc.

*Watch for winter annual and other early season weeds, any patches of herbicide resistant weeds?

*Storage areas cleaned and ready to accept upcoming hay harvest?


*Finish corn planting by May 15, if soil conditions allow

* Determine plant populations, make notes on germination problems

* Gaps in row? Check for seed corn maggot, wireworm, seedling blights, birds, seed placement issues

* Check no-till fields/fields with high residue or weeds for slug damage

* Monitor for weeds, note presence of "who", "how many" and "where"

* Adjust post emergence weed control actions

Small Grains:

* Monitor winter grains for crop stage, insect and disease problems

Check wheat for powdery mildew and soil borne wheat mosaic virus (susceptible varieties such as Harus and Jensen)

* Evaluate crop for adequate stand and plant vigor

Alfalfa & Hay:

* Monitor alfalfa seedings for weeds, insects & diseases.

* Check established alfalfa stands for alfalfa weevil, weed and disease problems.

* Timothy stands: check fields for symptoms of cereal rust mite

* Storage areas cleaned and ready to accept upcoming harvest?


* Field preparations, planter ready, Rhizobium inoculum?

Dairy Livestock Barn Fly Management:

* Sanitation, sanitation, sanitation - clean animal resting areas, feed troughs, minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard

* Check waterers, drainage, roof gutters for leaks and potential overspill

* Begin fly monitoring: install "3X5" index card fly speck monitoring cards through out barn

* Order fly management materials: fly tapes, insecticide baits, natural enemies (parasitoids)


*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 recently used equipment: tractors, tillage implements, planters, etc. as they are cleaned and serviced.

* Service corn planter as needed. alfalfa harvesting equipment, and tillage implements

* Soybean planter and alfalfa harvesting equipment ready?

* 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.

Up-coming events

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Small Grains Field Day

June 5, 2008

Cornell Research Farm at Aurora, NY

Seed Growers Field Day

Tuesday July 8

NYSIP Foundation Seed Barn

Cornell University, Ithaca, NY

Contact Information

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Julie Dennis: IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 252-5440

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

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