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Weekly Field Crops Pest Report 2007

April 24, 2007                Volume 6 Number 2

1. View from the Field

2. Early Season Alfalfa Root Diseases

3. Hessian Fly in Winter Wheat

4. Roundup Ready Alfalfa Cannot be Planted This Year!

5. Know When Weeds Wake Up and Maintain Good Corn Yields

6. Foliar Early Season Fungal Diseases of Wheat and Other Cereal Grains

7. CORRECTION: Planting Bt Corn this Year-Don’t Forget the Refuge!

8. Russ Hahn’s Weed Alert

9. Looking for Cornell Pest Management Guidelines on-line?

9. Clipboard Checklist

10. Contact Information

View From The Field

Eastern NYS
Ken Wise, NYS IPM

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Western NY and Finger Lakes-Julie Dennis, NYS IPM

We have a new feature in this week’s pest report:  Russ’s Weed Alert.  Every few weeks, we’ll tap into the expertise of Russ Hahn, Weed Scientist Extraordinaire, from Cornell’s Department of Crop and Soil Science.  Please let us know if this is a useful feature, and please drop us an email if you have a suggestion for a question for Russ to address. 

I have nothing to report from field visits yet. All I caught in a sweep net in alfalfa last week was snow!  I’ve seen my first mourning cloak butterfly of the season, a sure sign of spring.  Stay tuned for early season pest sightings next week.

Eastern NYS-Ken Wise, NYS IPM Program

News from Eastern NYS is limited to what I have seen at the Cornell Research Farm at Valatie. Tom Kilcer is evaluating triticale varieties for a forage study and some of them appear to be susceptible to snow mold. We are now evaluating the different varieties for the level of infection that occurred with snow mold.

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I saw what appears to be Stagonospora nodorum blotch in tritical and a rye cover crop at the Cornell Research Farm at Valatie. The disease appeared on the leaves touching the soil surface. See more about this disease in the article below.

xx

Statewide - Keith Waldron, NYS IPM Program

Dairy Fly Management - IPM Teleconference - May 3, 2007

Summer is just around the corner and with it the fly season for livestock producers.. If you are a dairy producer or work with them you might be interested in participating in an upcoming Dairy Fly IPM Training Teleconference.

A two hour Dairy Fly Management Integrated Pest Management (IPM) teleconference is now scheduled for Thursday, May 3, 2007. This northeast SARE sponsored program will provide extension personnel, producers, veterinarians and other agriculture professionals with an overview on what one needs to know about managing house and stable fly populations in confined dairy facilities. The workshop will present IPM principles and practices to help producers avoid, minimize, or manage dairy house fly and stable fly populations. Topics will include pest identification and biology, assessment techniques, management including discussions on cultural control, biological control using natural enemies, trapping, insecticides including insecticide resistance and suggestions for additional resources. A portion of the program will be devoted to a "questions from the audience" session.

This workshop will be held on Thursday, May 3, 2007 from 10 am until noon. This workshop will be offered via using live video conferencing and as a web streamed broadcast. To help us in our planning we ask those interested in participating contact Keith Waldron (jkw5@cornell.edu, 315-787-2432, c/o NYS IPM Program, NYSAES, Geneva, NY 14456).. When corresponding please provide your facilities technical contact person for video conferencing, the IP address that you would be viewing from for live video or the email address you would use if participating by "webstreaming".

Early Season Alfalfa Root Diseases

Ken Wise, NYS IPM

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There are many potential causes of alfalfa winter kill often involving some type of root disease.

Crown rot, one of the possible problems can occur in older fields with a history of stress, heavy traffic or grazing, poor drainage, fertility and pH problems, previous insect damage, etc. Plants exhibiting crown rot appear stunted and have few stems. Crown rot progresses slowly in the crown and taproot area of the plant. In many situations, crown rot cannot be attributed to a single pathogen. Several fungi (Fusarium spp., Phoma, Pythium, Rhizoctonia) as well as some bacteria, have been implicated in the disease. Often, a complex consisting of several of the pathogens attacks the plant. The way to tell if a plant has the disease is to dig up (not pull up) a plant showing symptoms. Then use a knife to split open the crowns and roots. Healthy tissue should be white, moist, and firm. Rotted tissue usually has a black or brownish- red color, but the color may vary from yellowish to pinkish or gray.

Another common alfalfa problem observed this time of year is frost heaved crowns. Low areas of the field that tend to accumulate water are sites worth checking for this ailment. Frost heaving may indicate potential disease problems such as Pythium or Phytopthora root rot which attack lateral and main root systems leaving plants with limited holding power for staying in the ground.

Hessian Fly in Winter Wheat

Julie Dennis, NYS IPM

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Hessian flies are making their presence felt in Missouri and Oklahoma in the past couple of years, and last year, an infestation was found near Lafayette, Indiana, for the first time in 10 years.

When you are scouting wheat, look for stunted, dark green plants.  Another tell-tale sign is that stems of infested plants are thickened. Look for larvae or pupae tucked in to the tight leaves around the base of the plant.  The pupa has the characteristic “flax seed” appearance.

Keeping track of when and where infestations of Hessian fly occur is of interest to researchers and other farmers. Please alert your local cooperative extension educator if you find an infestation.

Planting wheat crops after the Hessian fly free date is common practice, especially since this practice also decreases the risk for other disease and insect pests.  When planting winter wheat as a cover crop, Hessian fly free dates may be overlooked given that growing a harvestable grain crop is not the priority.  However, planting cover crop wheat after the fly free date remains important.  In some areas of the country, entomologists speculate that Hessian fly populations may be building up in areas because of the planting of wheat as a cover crop before the Hessian fly free date.

Roundup ready alfalfa cannot be planted this year

Julie Dennis, NYS IPM

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As the weather warms up, the possibility of spring seedings is looking a little less hopeless than it was a week ago! 

To remind our readers of a court decision in California on March 12, 2007, glyphosate resistant alfalfa seed can no longer be purchased.  Additionally, any seed that may be on hand from last season can no longer be planted.  (Those states to our south and west were permitted an exemption until March 30th.)

The court ruling was made based on the argument as to whether the USDA conducted proper testing of glyphosate-resistant alfalfa prior to its approval in June of 2005.  Of specific concern to organic producers and conventional alfalfa seed producers is the risk of unwanted pollen movement from glyphosate-resistant varieties to non-resistant varieties under normal production settings. The feed safety of glyphosate resistant alfalfa is not brought into question.

If you are interested reading more from the legal end of things, here is the court filing from the U.S. District Court for the Northern District of California.

Know when weeds wake up and maintain good corn yields!

Ken Wise, NYS IPM

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It is important to know approximately when you might see certain species of weeds in the field. By knowing when certain species of weeds emerge, selection of the best control measures can be employed. Remember that in corn, early weed control is critical. If you let corn grow beyond the v3 to v4 stage of growth without controlling weeds you start to lose yields very quickly.

We can break weeds down into categories based on the accumulation of growing degree-days (GDD)(48F Base Temp.) as a means of predicting when plants might start to emerge:

Group 0 (Emergence occurs in fall or early spring)
Winter annuals normally complete emergence prior to planting of corn.
Examples: horsetails (mares tail), white cockle, field penny cress, shepherd's purse

Group 1 (Emergence begins several weeks prior to corn planting, GDD <150)
Examples: giant ragweed, lambsquarters, Penn. Smartweed, common sunflower

Group 2 (Emergence begins soon before or at corn planting, GDD 150-300)
Examples: common ragweed, green foxtail, velvetleaf

Group 3 (Emergence begins at the end of corn planting season, GDD 250-400)
Examples: yellow foxtail, black nightshade, common cocklebur, wild proso millet

Group 4 (Emergence begins after corn emergence, GDD 350 >)
Examples: large crabgrass, fall panicum, waterhemp, morning glory species

(Source: Purdue Field Crops Pest Management Handbook)

Foliar Early Season Fungal Diseases of Wheat and Other Small Grains

Ken Wise-NYS IPM

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Stagonospora nodorum blotch: I found Stagonospora nodorum blotch on the lower leaves in a rye cover crop at the Cornell Research Farm at Valatie on Friday April 20. Splashing rain or thunderstorms can move spores from soil surface on to the plant. This fungal pathogen may also reside in residue on the field surface. In wheat, greatest yield losses occur when the flag leaf and the next two lower leaves become infected by the time the wheat flowers in late May. Leaf lesions begin as very dark brown flecks or spots, sometimes with a yellow halo. These small irregular lesions expand into oval light brown lesions with dark brown centers. As lesions enlarge, they become dark brown and the centers turn grayish-white in color as tiny brown or black dots (pycnidia) develop within them.

Powdery Mildew: While I have not seen Powdery Mildew this year, it is a common disease of cereal grains in NYS. Powdery mildew forms a white to gray, fungal coating on the above-ground parts of the wheat plant. Lower leaves are usually the most severely infected because of the high humidity in the lower canopy. As disease lesions age, small black fruiting bodies (cleistothecia) develop with in white infected areas. Powdery mildew is favored by wet and humid days with moderate temperatures of 600 F or above. Powdery mildew is disseminated by airborne spores.

Leaf Rust: Leaf Rust does occur in NYS and is commonly found in Late April through June.  Rust lesions are small, circular, and vivid orange in color. They may occur on stems, but are most common on the upper surface of leaves. Leaf rust is favored by warm and humid weather with thunderstorms in June. Leaf rust is disseminated on by winds which carry the airborne spores great distances. Temperatures between 600 and 800 F are optimal for disease development.

Thresholds and Management

Thresholds for foliar fungal diseases of wheat are based on potential yield and the level of infection of the disease in the field. For Economic Thresholds and making decisions on fungicides please refer to the 2007 Cornell Guide For Integrated Crop Management On-line, or more specifically:

5.7.4 Guidelines for Wheat Fungicide Decisions

Correction!
Planting Bt Corn This Year?  Don’t Forget the Refuge

Julie Dennis, NYS IPM

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Because of a typo in an article last week, let’s review the refuge concept for using Bt rootworm corn for control of corn rootworms one more time!

Why is a refuge planted?

  1. To keep a portion of the population from being exposed to the Bt toxin
  2. To prevent the development of CRW or ECB populations resistant to Bt

Because the EPA requires growers by law to plant a refuge - 20% of the acres must be planted to corn without the Bt trait.  When the seed is purchased, an agreement to plant the refuge is signed.

If pests become resistant, this tool will be lost. (Remember, having more options available allows us to better implement IPM!)

Here’s a brief overview of refuge requirements for Bt Rootworm corn:

  • (The refuge requirements are more strict for CRW than for ECB, so if CRW requirements are followed, you’re all set for both pests)

  • Plant at least 20% of corn acres with a corn hybrid that does not contain Bt technology for CRW

  • The refuge can be treated with soil insecticide or seed applied insecticide, but NOT with other Bt insecticides

  • Plant the refuge at the same time as the Bt corn, in a field with similar crop history

  • Plant the refuge within the field or in an adjacent corn field (your neighbor’s corn field is NOT considered your refuge!)

Options for the configuration of refuge include:

  • Adjacent to Bt corn field (not further away than a road, path, or ditch)
  • Field end rows or field perimeter

Mixing of non-Bt seed with Bt rootworm seed for inter-planting is not permitted

Russ’s Weed Alert

Russ Hahn (with Julie Dennis, NYS IPM)

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This week, I asked Russ Hahn to update us on new herbicides available for the 2007 season.  Below he describes the results of recent research conducted in 2006 on Resolve herbicide.

“Resolve (rimsulfluron) was registered in March 2006 for use on field corn in NY State.  Rimsulfuron is a sulfonylurea herbicide that is also marketed as Matrix for use on potatoes and as component in Basis, Steadfast, and Steadfast ATZ for field corn.  The sulfonylurea herbicides are ALS (acetolactate synthase) inhibitors and are in GROUP 2 site of action classification.  Resolve is being marketed for added residual and/or burndown activity on emerged weeds in preplant or preemergence (PRE) programs, in planned PRE followed by postemergence (POST) programs, and in total POST programs with glyphosate in Roundup Ready corn.

“Although limited research had been done with Resolve in NY prior to 2006, additional research was done this past season to accumulate information on the residual activity of this product.  Resolve was included in PRE treatments and in early postemergence (EPO) combinations with glyphosate at Aurora and Valatie in 2006.

“At Aurora, 1.5 oz/A of Resolve alone and a tank mix of 1.5 oz/A of Resolve + 1 qt/A of AAtrex were compared with a PRE standard of 2.5 qt/A of Lumax + 1 pt/A of AAtrex in an experiment planted May 25.  PRE treatments were sprayed May 30.  Rainfall was plentiful for herbicide activation with 6.25” inches recorded during June.  Common ragweed and giant foxtail were the dominant weeds.  The Lumax + AAtrex combination controlled 73% of the ragweed while Resolve and Resolve + AAtrex treatments controlled 50 and 97% of the ragweed respectively.  Foxtail control was 98% with Lumax + AAtrex and averaged about 65% with the two Resolve treatments.

“At Valatie, 1.5 oz/A of Resolve alone and a tank mix of 1.5 oz/A of Resolve + 1 qt/A of AAtrex were compared with 2.5 qt/A of Lumax + 1 pt/A of AAtrex in an experiment planted May 24.  PRE treatments were sprayed May 25.  Following PRE treatments, rainfall was 0.92 inches in May and 9.35 inches in June.  At this site, dominant weeds were common ragweed and large crabgrass.  The Lumax + AAtrex combination controlled 96% of the ragweed while the two Resolve treatments averaged 75% ragweed control.  Crabgrass control was 97% with Lumax + AAtrex and averaged 55% with the two Resolve treatments.

“The combination of 1 oz/A of Resolve + 1 pt/A of AAtrex applied with 24 oz/A of Touchdown Total was compared with a reduced rate of Lumax (1.5 qt/A) with Touchdown Total at Aurora and Valatie.  Weeds were 1 to 3 inches tall at the time of EPO application.  These Lumax and Resolve treatments with Touchdown Total controlled 97+% of the ragweed compared with 91% ragweed control with Touchdown Total alone.  At Aurora, the Lumax + Touchdown Total tank mix controlled 99% of the giant foxtail while Resolve + AAtrex + Touchdown Total  controlled 60% of the foxtail.  With crabgrass at Valatie, both the Lumax and the Resolve + AAtrex combinations with Touchdown Total provided excellent crabgrass control (98+%).”

Russ advises that Resolve is not a weed management “silver bullet” that will replace other herbicide options.  “While Resolve demonstrates significant residual activity, it is not clear that it has distinct advantages over more familiar residual herbicides” says Russ.  Another important point that Russ emphasizes is that Resolve is a sulfonylurea herbicide, and there are more weeds resistant to herbicides with this site of action (Group 2 Herbicides) than any other site of action.

Looking for Cornell Pest Management Guidelines on-line?

Keith Waldron, NYS IPM

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See Pest Management Guidelines for your one stop Cornell guidelines information connection. This website has links to all Cornell Pest Management Guidelines On-Line including: Berry Crops, Field Crops, Floral and Greenhouse Crops, Grapes, Herbaceous Perennials, Livestock, Pests Around the Home, Tree Fruit, Trees and Shrubs, Vegetable Crops and Wildlife Damage Management.

Cornell Guide to Integrated Field Crop Management

Clipboard Checklist

Keith Waldron-NYS IPM

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General:

  • Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks.
  • Observe wet areas and plot on aerial photo of farm for future drainage considerations and crop decisions

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

  • Watch for early season weeds: winter annuals, chickweed, henbit, field penny cress, shepherd's purse, giant ragweed, lambsquarters, Pennsylvania  smartweed, common sunflower

  • Store snow shovel, summerize sno-blower?

Alfalfa and Small Grains:

  • Monitor alfalfa for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin  counties)

  • Monitor alfalfa for Alfalfa weevil as weather continues to warm

  • Evaluate established legume stands for winter damage, determine average alfalfa stand count, adjust crop plans if necessary

  • Monitor winter grain fields for overwintering survival, virus disease symptoms, goose damage

Corn:

  • Prepare land for corn if it is dry enough and begin planting the last week of April if it is dry (even if it is cold!)

  • Calibrate corn planter

Pastures:

  • Check and mend fences as needed.

  • Check crop growth

  • Review/Plan rotation system

Storage:

  • Check forage allocation and anticipate feed program adjustments as forages from previous year are used up

  • Plan where forages should be stored for optimum allocation next feeding season

Equipment:     

  • Arrange for custom weed control or check your own application or cultivator equipment for repairs.   

  • Check nozzles, pumps, etc., recalibrate pesticide application equipment regularly before use.

  • Calibrate manure spreaders - maintain records on amount spread per field

Contact Information

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Julie Dennis:
IPM Area Educator, Livestock and Field Crops, Western NY
Phone: (315) 331-8415
Fax: (315) 331-8411
Email: js38@cornell.edu

Keith Waldron: NYS Livestock and Field Crops IPM Coordinator
Phone: (315) 787 - 2432
Fax: (315) 787-2360
Email: jkw5@cornell.edu

Ken Wise: Eastern NYS IPM Area Educator: Field Crops and Livestock
Phone: (518) 434-1690
Fax: (518) 426-3316
Email: klw24@cornell.edu