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NY Weekly Field Crop Pest Report, 2005

August 12, 2005 Volume 4 Number 17

1. View from the Field

2. What Pest Problems to Consider When Planting Wheat

3. How Important is European Corn Borer in Field Corn?

4. Check for Stalk Rots

5. Growing Degree Days in NYS

6. Clipboard Checklist

7. Contact Information

View from the field

Eastern NYS

Ken Wise

Western NYS

Julie Stavisky

On top of seeing a lot of drought stressed corn and soybeans I have seen an excess of corn ear damage created by deer, birds and even chipmunks. The husk covering the corn was pulled back and about a third of the grain was gone. Some of the ends of the ears were bitten right off by deer. In addition, the open husk can allow a variety of diseases to infect the ear of corn. Some of these diseases might be: Common smut, Fusarium ear rot, Gibberella ear rot, Diplodia ear rot, Cladosporium ear and kernel rot, and more.

File written by Adobe Photoshop® 4.0

Substantial rainfall in parts of Cayuga, Seneca, Wayne, and Ontario Counties this week provided much-needed relief for soybeans and corn. Rain will also help in the battle against spider mites. Natural enemies of spider mites (including predators and fungal pathogens) can do a great job of alleviating a spider mite infestation in soybeans, but the natural enemies are moisture-dependent.

Spider mites continue to pose a threat to soybeans in Orleans County, and Mike Stanyard (NWNY Team) reports on a serious spider mite infestation in Monroe County.

Reports of white mold in soybeans have come in from Cortland County.

What pest problems to consider when planting winter wheat.

There are several factors to consider when planting winter wheat. The first is to never plant wheat in the same field two years in a row. By rotating you reduce the risk of several diseases like eyespot foot rot, powdery mildew, leaf rust, stagonospora nodorum blotch, glume blotch and more. The second item to consider is what winter wheat variety to plant. Of course you will look at potential grain yield, grain test weight and straw quality. It is also important to consider resistance to diseases in the varieties you select. Diseases of particular concern are wheat spindle streak mosaic virus, soil borne mosaic virus, yellow dwarf virus (formally called “barley yellow dwarf virus”), powdery mildew, leaf & stem rust and/or other disease problems your farm has had in previous years. For a list of potential wheat varieties consult your Cornell Guide for Integrated Field Crop Management (available online at www.fieldcrops.org). Next, remember to plant AFTER the Hessian fly free date. By doing so, not only are you avoiding infestations of Hessian fly but also certain aphids that can transmit yellow dwarf virus. The following figure shows the “Hessian Fly Free Dates” in NYS:

File written by Adobe Photoshop¨ 4.0

The use of certified wheat seed should be considered. When seed is certified you can be confident of the quality and it is void of diseases and weed seed. Next is to remember to always use a fungicide seed treatment to protect the crop from certain seed and seedling related diseases. Another core consideration is having a sound fertility program. When a plant is healthy it can complete with weeds and may tolerate more insect pest pressure and still maintain good yield.

How important is European Corn Borer in Field Corn?

Julie Stavisky, NYS IPM

Catches of European corn borers (ECB) in pheromone traps have increased dramatically over the past 2 weeks. The trapping data is available from The Sweet Corn Pheromone Trap Network coordinated by Abby Seaman with the NYS IPM Vegetable program. The increase in numbers of ECB indicates that the second generation of moths is flying. While ECB causes much less worry in field corn than in sweet corn, concern about severe ECB infestations and the disease problems that may follow requires our attention.

The primary injury from the second generation of ECB is caused by the larvae tunneling into stalks and ear shanks (see photo), which can result in poor ear development, broken stalks (see photo), and dropped ears. The later in the kernel-filling period that an ECB infestation starts, the lower the yield impact will generally be.

To scout for ECB in August, look for egg masses on the undersides of leaves near ear level on the plant. Tunneling larvae can be found by looking for areas of frass (insect droppings) at the point of entry into the stalk.

At times, a large infestation of ECB may cause a localized problem. Late harvesting and/or adverse weather conditions that cause plants to break at the points of injury may exacerbate those losses. Although the ECB damage can be conspicuous on an occasional plant, it does not generally cause significant yield losses in NY in corn harvested for grain or silage. However, drought stress conditions (which corn is experiencing in many locations in NY this year) can magnify the effects of ECB damage. Another reason to be concerned with an ECB infestation is that stalks or ears injured by ECB can be the entry point for disease-causing organisms. For more information, see Ken’s stalk rot article!

Check For Stalk Rots!

Ken Wise, NYS IPM

It is important to monitor your fields for stalk rots as you start thinking of your corn harvest. If you have an infection of stalk rot it can cause the plant to die early losing grain or silage yields. Stalk rots are caused by many different fungi that enter the plant. They occur when the plant is under stress or when it may be injured by insect pests, hail, deer and bird damages, drought or soil saturation, lack of sunlight, extended cool weather, and the lack of fertility. The following are symptoms of specific stalk rots:

Anthracnose stalk rot symptoms may appear after tasselling as vertical, tan to reddish brown, water-soaked lesions (streaks) in the stalk rind. Lesions become large, dark brown to shiny black. Fields with high amounts of anthracnose leaf blight (both diseases have the same causal agent) should be checked for indications of anthracnose stalk rot.

Diplodia stalk rot symptoms may appear as numerous black pycnidia in the lower internodes of the stalk. The black dots are the size of a pinhead or smaller. When conditions are wet a white mold may develop on the stalk surface.

Fusarium stalk rot normally starts just after pollination and symptoms appear later in the season. When you cut open the stalk, the pith appears as a whitish to pink (salmon) color. There are also distinctive brown streaks on the lower internodes.

The first symptom of gibberella stalk rot is the onset of grayish-green color of the leaves. The stalk will turn dark green to tan near the base of the plant. The pith of the stalk becomes soft and will appear as a red to pinkish color.

Pythium stalk rot normally appears as a decay of the first internode above the soil. The pith will become soft, turn brown and appear water-soaked. Many times the stalk can twist and/ or lodge. Even though it may have lodged the plant will stay green for several weeks because the vascular tissue is not destroyed.

If you discover certain stalk rot diseases make notes of the hybrid, tillage methods, rotation history, and planting date. By doing this you be able to avoid the disease occurrence in the future. The following is the effectiveness of specific management practices for stalk rots:

Resistant Crop Clean Plow

Corn Disease Variety RotationDown of Residues Fungicides

Stalk rots

Anthracnose 1 1 1 4

All other 2 3 3 4

1= highly effective, 2= moderately effective, 3=slightly effective, 4= not effective, 5 = not usually economical,

Reference: Purdue University Field Crops Pest Management Manual

As with most diseases that attack corn, if you can reduce stress on the plants you most likely can reduce the occurrence of certain stalk rots. Having a sound fertility program based on soil testing is important for keeping a corn plant healthy. Select a hybrid with resistance to certain diseases and good standability that is adapted to your region. Some of these stalk rots can produce mycotoxins that can be toxic to livestock. You should consider having silage tested for certain mycotoxins if you had fields with stalk rots this season. For more information on corn diseases checkout our online publication: IPM for Corn Diseases

Growing Degree Days in NYS

March 1 - August 11, 2005


Base 50 F





Clifton Park








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

Clipboard Checklist

Keith Waldron,



• 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.


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

• Monitor corn rootworm adults at silking.


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


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