Weekly Field Crops Pest Report 2009

View from the Field

Ken Wise
NYS IPM

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This was the first week I was able to get down to the Cornell Alfalfa Research plots at SUNY Cobleskill. The alfalfa looked very good. I could not find any signs of early season foliar diseases. I discovered many alfalfa weevil adults in the older fields at the farm. See the article below for more information on alfalfa weevil.  I did find some adult Clover-root curculio weevils. Clover-root curculios can often be found cruising alfalfa this time of year. Unfortunately, there is not much we can currently do to manage this insect with the exception of rotating to a different crop. This pest builds in population in a field over time. These small weevils are 1/8 inch long and 1/16 inch wide with short, broad snouts. The adult weevil is brownish-black and covered with grayish hair and scales. Adult curculios chew the margins of leaves leaving C shaped notches.

Clover-root curculio larvae feed below-ground on nodules, small rootlets, and chew out portions of the main root. As a result of larval feeding on roots, diseases such as fusarium crown and root rot can enter the plant. Clover-root curculio will feed on several types of clover and alfalfa. 

I also found a tiny blue weevil 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.

Foliar Early Season Fungal Diseases of Wheat and Other Small Grains

Ken Wise
NYS IPM

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Stagonospora nodorum blotch: I have seen small amounts what appears to be Stagonospora nodorum blotch on triticale at the Cornell Research farm in Valatie this spring (April 23). 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 2008 Cornell Guide For Integrated Crop Management On-line: www.fieldcrops.org or more specifically: Guidelines for Wheat Fungicide Decisions

Hessian Fly in Winter Wheat

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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.

Looking for Cornell Pest Management Guidelines on-line?

Keith Waldron
NYS IPM

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See http://ipmguidelines.org/ 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: WWW.fieldcrops.org

National Asian Soybean Rust Report

Gary C. 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

Ken Wise
NYS IPM

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Adult alfalfa weevils are now moving back into established alfalfa fields. Remember alfalfa weevil populations can build up over the life of the alfalfa stand. The longer an alfalfa field is in production the higher the risk of alfalfa weevil damage. Adult weevils that enter fields in the spring are light brown and 3/16" long. They have a band of darker brown down the center of their back and a long snout.

If you keep track of growing degree days you can predict when certain stages of alfalfa weevil development occur. Remember that alfalfa weevil’s base temperature for determining its growth stages by growing degree days is 48 degrees F. You should start scouting and sampling fields at about 350 growing degree days. For more information on alfalfa weevil, view the Alfalfa weevil management guide.

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

(Note: for alfalfa weevil predictions use Base Temp of 48F)

CURRENT Accumulated Growing degree days (48F Base)

Check out these websites for correct identification: Alfalfa Weevil Eggs and Alfalfa Weevil Larvae. Check out our on-line publication, IPM for Alfalfa Weevil.

Remember the base temperature for alfalfa weevil is 48F to determine developmental growth stage.

March 1 -  April 28, 2009

*Indicates missing data

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, purple deadnettle, field penny cress, shepherd's purse; annuals: 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 (thinning stand, frost heave, Brown Root Rot), determine average alfalfa stand count, adjust crop plans if necessary
*Monitor winter grain fields for over wintering survival, virus disease symptoms, weed pressure, goose damage

Corn:
*Pre-plant weed evaluation
*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!)

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

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.
*Check/tune up corn planting equipment
*Calibrate planting equipment - maintain records on crop planting rate per field
*Calibrate manure spreaders - maintain records on amount spread per field

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

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
Email: klw24@cornell.edu

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