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NY Weekly Field Crop Pest Report, 2005

August 5, 2005 Volume 4 Number 16

1. View from the Field

2. Phytophthora Root Rot in Soybean

3. Is Armyworm “Falling” into Your Field?

4. Soybean Aphid Data Collection Need!

5. Growing Degree Days In NYS

6. Clipboard Checklist

7. Contact Information

View From the Field

Western NYS

Julie Stavisky

Eastern NYS

Ken Wise

I’ve seen numerous western and northern corn rootworms in late-planted continuous corn in Ontario County. In Wyoming County, potato leafhoppers continue to be difficult to find in alfalfa. In several alfalfa fields in Ontario County (new seedings and established stands), leafhoppers are abundant but below threshold. Mike Stanyard (NWNY Team) reports that he has seen fungal pathogens causing soybean aphid mortality in Wayne County. With the recent hot, humid weather and heavy morning dews, conditions have been ideal for development of these fungal pathogens. Watch here for photos next week! Reports from Cayuga County indicate that soybean aphids are in decline many places thanks to predators. Also in Cayuga County, grasshopper damage is prevalent, but below economic levels. Nancy Glazier (NWNY Team) checks in with a report from the soybean fields she is scouting in Orleans County: One field has 600 to 800 aphids per plant and numbers are still on the rise. Downy mildew is present in many fields.

Soybeans: During a Soybean TAg meeting Thursday night we observed soybean aphids that ranged for 10 to 50 per plant. This is well below threshold. There were also several lady beetles in the field feeding on the aphids.

File written by Adobe Photoshop® 4.0

A few of the growers stated that they had several grasshoppers in a few of their bean fields. They indicated that the grasshoppers were feeding in the leaves and showed about 20 % damage. Soybeans can withstand up to 35 % leaf feeding without losing yield. The following is a picture of a grasshopper on the soybeans:

File written by Adobe Photoshop® 4.0

Phytophthora Root Rot in Soybeans

Julie Stavisky, NYS IPM

Some areas of plants affected by Phytophthora root rot (PRR) have been seen in soybean fields recently. The symptoms include significantly rotted roots, dark brown or black scars on the stem from the soil line up, and wilting followed by death of leaves at the top of the plant. A photo of the stem injury is shown in the following link:

http://pdc.unl.edu/soybean/phytophthora/stemrot.htm

PRR is caused by a water mold. In a dry year like this season, the disease is most prevalent in low areas of fields and fields with poor drainage due to compaction or soil type. In a wetter year, PRR can affect plants even in well-drained soils.

If a large area of a field is severely affected or killed by the disease, PRR may have an impact on yield. In less severe situations, the ability of soybean plants to compensate for yield when an occasional plant dies will typically prevent significant yield losses.

Many common crop management practices prevent PRR from becoming a serious problem in soybeans. When PRR is of concern, management strategies include improving field drainage, planting resistant varieties, and rotating to another crop.

Is Armyworms “Falling” in to your fields?

Ken Wise, NYS IPM

Lewis and Jefferson counties have been reporting some corn fields with armyworm damage. Most likely this time of the year it the pest would be fall armyworm. Fall armyworm larvae are green, brown, or black about 1/8 inch to 1 ý inches long and have a dark head capsule usually marked with a pale, but distinct, inverted "Y." Along each side of its body is a longitudinal, black stripe, and along the middle of its back is a wider, yellowish-gray stripe with four black dots on each segment. Larvae are active at night, but can be seen feeding on overcast days. Larvae will hide under the canopy of the grass during the day. You will need to be aware that armyworms can move from field to field every quickly. Fall armyworms can show up starting in late June. This armyworm seldom causes economic losses in corn. If there are sufficient numbers and damage is present, an insecticide could be justified. Treat only the affected area and a 20 to 40-foot border around the infestation. (Note: the corn maybe too tall to treat with an insecticide). Rarely does a whole field need to be treated for armyworm. Larger armyworm larvae, greater than 1.5 inches long, are much more difficult to control. These large larvae are more tolerant of insecticides, reducing the effectiveness and economic viability of this option.

Soybean Aphid Data Collection Need!

Keith Waldron, NYS IPM

Soybean Aphid threshold values for SBA populations have not been extensively tested in NY. More field data is needed to establish and validate practical threshold guidelines

• If you have soybeans at the early pod fill growth stage (or earlier), Soybean aphid populations have reached the 250 per plant recommended threshold and you plan to treat the field with an insecticide….

We Need Your Help!

Side by side field trial data with insecticide treated vs. non treated check strips is critical to refine our New York threshold recommendations for managing soybean aphids.

If you have fields meeting the conditions described above and would like to participate..
Please contact your local Cooperative Extension office or the NYS IPM Program office at 315 - 787 - 2432, jkw5@cornell.edu.

Data needed:
-
Soybean aphid population assessments

- average number of SBA's per plant

-Soybean variety, growth stage at time of treatment
-Insecticide used, rate of application
-Yield information, date of harvest
-Field Location, grower contact information

PLEASE RECORD THE FOLLOWING:
Grower contact information
Field location (GPS if available)
Date Treated
Average number of SBA's per plant pre-treatment
Soybean growth stage

Insecticide Treated Not Treated with Insecticide

Insecticide used
Rate of application
Date of harvest
Yield
Comments

Growing Degree Days in NYS

March 1 - August 4, 2005

Location

Base 50 F

Batavia

1463*

Chazy

1387

Clifton Park

1936

Geneva

1556

Ithaca

1497

Prattsburg

1367

*missing data

Source: http://newa.nysaes.cornell.edu/

Clipboard Checklist

Keith Waldron, NYS IPM

General:

• Maintain crop production activity records by field, including harvest date, pesticides used, nutrient inputs including manure, etc.

Alfalfa & Hay:

• Continue monitoring for potato leafhopper- harvest early or spray on basis of need.

• Monitor for diseases and record information on type and location for future cropping decisions.

Corn:

• Monitor for foliar and stalk diseases, nitrogen and other nutrient deficiencies, European corn borer, weeds.

• Monitor corn rootworm adults at silking.

Soybeans:

• Monitor for soybean aphid, soybean rust, foliar diseases.

Livestock:

• Continue livestock facility sanitation management (manure, feed bunks and storage areas, waterers, etc.). Cleaner, less fly production

• Mow around facilities to minimize rodent habitat.

• Monitor young stock for cattle lice and mange mites

• Check condition of pastures and animals on pastures

- Evaluate need for face fly and stable fly control measures

- Check and clean pasture water supplies.

Contact Information

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