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Weekly Field Crops Pest Report 2006

April 18, 2006 Volume 5 Number 1

1. View from the Field

2. Alfalfa Winter Kill, Root Diseases and Frost Heaving

3. Status of Winter Wheat: Diseases to Watch For!

4. Soybean Rust Center

5. Clipboard Checklist

6. Contact Information

View From The Field

Ken Wise-NYS IPM

Coming to you again is the 2006 season opener of the “NYS IPM Field Crop Pest Report.” Like last year this will be a statewide email and on-line publication. The purpose of this publication is to provide Field Crop Extension Educators with weekly updates on field crop pests. As in past years, we encourage our readers to use the material provided in the weekly report in their extension programming and newsletters. We greatly appreciate any contributions of pest information and feedback so that we can continue to make the pest report a useful resource for our audience!

While scouting alfalfa this last week at the Cornell University Research Farm in Valatie I observed some over-wintering injury. Most likely this was a combination of root disease and frost heaving. For more information see article below. No signs of alfalfa weevil in the fields as of last Friday. With the warmer weather we have been experiencing we most likely will begin to see this insect pest soon.

I found a tiny blue weevil last Friday called Ischnopterapion virens, aka clover stem weevil a pest of clover. This weevil is native to Europe and is relatively new to the United States. Adults are metallic blue, about 3/16 inches long, with a distinctive snout and straight antennae. Adults make small circular holes in leaves of white clover. Larvae tunnel in the runners of clover and stems of red clover. The economic damage status of this weevil is not known.

Alfalfa Winter Kill, Root Diseases and Frost Heaving

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, getting as much of the tap root as possible. Then use a knife to split open the crown and root. 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 (see photo below).

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. The photo shown came from a field in Freeville NY (Year 2004) which was poorly drained and had a history of Phytopthora root rot.

Status of Winter Wheat - Diseases to Watch For

Julie Stavisky-NYS IPM

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Many wheat fields I’ve observed this spring are greening up fast and growing well. But there are some problem areas, too. Bare spots in fields may be the result of unhealthy plants that do not grow vigorously in the spring due to infection with pathogens that cause root and crown rots.

Many different fungal organisms cause root and crown rot diseases of wheat, and it is often difficult to distinguish which causal agent is present. The most common organisms that cause root and crown rots include Fusarium and Pythium. Seedling blights and rots are more likely to be severe under excessively wet conditions and when soil temperatures are too low for good growth. Plants injured from frost heaving, resulting from repeated freezing and thawing, are especially vulnerable. Over the past winter, we didn’t have snow cover to insulate plants, so dormant plants were more exposed to the elements than usual.

Fusarium seedling blight: Seedlings and tillering plants infected with Fusarium seedling blight are generally stunted and yellow, and the crown, roots, or lower stem take on a brown to reddish-brown water-soaked rotten appearance. If plants survive, they have a brittle, stunted appearance and are paler green than healthy plants. Plant death can result in patchy stand reduction. The Fusarium fungi can survive in plant residue or as dormant spores in the soil for several moths.

Pythium root rot: The “water mold” that causes Pythium root rot may first infect the seedlings in fall-planted cereals, though seedlings are rarely killed. The stunting of seedlings resulting from Pythium infection may go unnoticed until other plants in the field begin healthy, vigorous growth in the spring. Roots of infected plants begin to turn brown then disintegrate beginning at the root tips. Plant mortality can occur if infection is severe enough for the rotted roots to break away from the crown. Pythium spores survive several years in soil without a host, and spores are present in all soil types. Infection of plants is greatest in cold, wet, clay soils.

Soybean Rust Updates

Julie Stavisky-NYS IPM

The USDA soybean rust website (http://www.sbrusa.net/) and the New York State Soybean Rust Information Center will continue to be our best first resource as things develop in the soybean crop this year.

Clipboard Checklist

Keith Waldron-NYS IPM

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* 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

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 virus disease symptoms

* 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!)

* Check and mend fences as needed.
* Check crop growth
* Review/Plan rotation system

* 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

* 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 Stavisky: 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

Previous Issues:
Weekly Field Crops Pest Report, 2005 -- Index 2005, 85k pdf file
Eastern New York Field Crops Pest Report, 2004
Eastern New York Field Crops Pest Report, 2003
Eastern New York Field Crops Pest Report, 2002